Keeping Children Safe: a multicentre programme of research to increase the evidence base for preventing unintentional injuries in the home in the under-fives

Research questions

The research questions addressed within six work streams in the KCS programme are outlined in the following sections and shown in Figure 1.

FIGURE 1.

The Keeping Children Safe programme of research.

Work stream 1

This work stream addressed the question, ‘What are the associations between modifiable risk and protective factors and medically attended injuries resulting from five common injury mechanisms in children under the age of 5 years?’ This question was answered by a series of five case–control studies exploring risk and protective factors for each of the three most common types of medically attended falls (falls from furniture, stair falls and falls on one level), poisonings and scalds. These five studies are collectively referred to as study A. In addition, a study to validate the self-reported exposures was nested within the case–control studies in study A, and this is referred to as study B.

Work stream 2

This work stream addressed the question, ‘What are the NHS and child and family costs of falls, poisonings and scalds?’ This was answered by a cohort study measuring costs and injury outcomes nested within the case–control studies in study A. In addition, as there were no validated tools to measure health-related quality of life (HRQL) in the short term following a range of injuries in the under-fives, this study also validated the toddler version of the Pediatric Quality of Life Inventory (PedsQL™)43 for this purpose. These two studies are referred to as study C, with the costs study referred to as the study C costs substudy and the validation of the PedsQL study referred to as the study C HRQL substudy.

Work stream 3

This work stream addressed the question, ‘What interventions are being undertaken by children’s centres to prevent thermal injuries, falls and poisonings?’. This question was answered by two national surveys of children’s centre managers and staff. These studies are referred to as study D.

Work stream 4

This work stream addressed the question, ‘What are the barriers to, and facilitators of, implementing thermal injuries, falls and poisoning prevention interventions among children’s’ centres, professionals and community members?’. This question was answered by three studies: first, a systematic review of the quantitative and qualitative evidence on barriers to, and facilitators of, injury prevention (study E); second, a qualitative study consisting of interviews with children’s centres managers and staff to explore their views on barriers to, and facilitators of, implementing injury prevention interventions in children’s centres (study F); and, third, a qualitative study of parents of injured and uninjured children to explore views on barriers to, and facilitators of, implementing home injury prevention nested in the case–control studies in study A (study G).

Work stream 5

This work stream addressed the question, ‘How cost-effective are strategies for preventing thermal injuries, falls and poisonings?’. This question was answered by systematic overviews and systematic reviews of the literature on preventing falls, poisonings, fire-related injuries and scalds (study H), a systematic review and pairwise meta-analysis (PMA) of home safety interventions (study I), network meta-analyses (NMAs) of interventions to promote smoke alarm use and promote falls prevention practices, poison prevention practices and scalds prevention practices (study J) and decision analyses of interventions found to be effective in the NMAs (study K).

Work stream 6

This work stream addressed the question, ‘How effective and cost-effective is implementing an IPB for one exemplar injury prevention intervention?’. This question was answered by a randomised controlled trial (RCT), set in children’s centres, which evaluated the effectiveness and cost-effectiveness of an IPB for the prevention of fire-related injury (study M). The trial was preceded by a review of the literature on the implementation and facilitation of health promotion interventions (study L) to inform the design of the intervention. Evidence from the trial was then incorporated into the development of a second IPB. This covered the prevention of fire-related injury, falls, poisonings and scalds, based on findings from studies A and D–M.

Research question

What are the associations between modifiable risk and protective factors and medically attended injuries resulting from five common injury mechanisms in children under the age of 5 years?

Methods

Five multicentre case–control studies were undertaken (study A). Cases were children aged < 5 years attending secondary care with a fall (three types: fall from furniture, fall on one level or a stair fall), poisoning or a scald. Control subjects (controls) were matched to cases on age, sex and calendar time, and were recruited from the register of the cases’ general practice (or neighbouring general practice). Exposures (safety equipment use, safety behaviours and hazards) were measured using parent-completed questionnaires and were validated by home observations in a sample of cases and controls (study B). Odds ratios (ORs) were estimated using conditional logistic regression adjusted for confounding factors.

Results

Conclusions

Despite a small number of apparently counterintuitive findings (indicated with an asterisk), a range of modifiable risk factors were associated with falls from furniture, falls on stairs, poisonings and scalds in children aged 0–4 years. These results provide evidence on which to base safety advice and recommendations.

Work stream 1 consisted of five case–control studies (study A) quantifying associations between modifiable risk factors and falls from furniture, falls on one level, falls on steps or stairs, poisonings and scalds. Work stream 1 also included a study to validate self-reported exposures in the case–control studies (study B). The findings from work stream 1 informed:

• the decision analyses undertaken in work stream 5

• the development of an IPB for the prevention of fire-related injuries, falls, poisonings and scalds undertaken in work stream 6 (see Chapter 7).

Objectives

The primary objectives of study A were to estimate associations between modifiable risk and protective factors and medically attended injuries resulting from five injury mechanisms in children aged < 5 years:

1. falls from furniture

2. falls on one level

3. stair falls

4. poisoning

5. scalds.

Our secondary objectives were to explore whether or not associations between risk and protective factors and injuries varied by child age, sex, ethnicity, single parenthood, housing tenure and unemployment and injury severity. 49

Study design

We used five multicentre matched case–control studies [one for each of the injury mechanisms (a)–(e)].

Setting

We recruited participants from EDs, minor injury units (MIUs) and hospital wards from acute NHS trusts in Nottingham, Bristol, Newcastle upon Tyne, Norwich, Gateshead, Derby, Great Yarmouth and Lincoln, UK. Recruitment of cases commenced on 14 June 2010 for all studies and finished on (a) 15 November 2011 for the falls from furniture study, (b) 15 November 2011 for the falls on one level study, (c) 30 September 2012 for the stair falls study, (d) 18 January 2013 for the poisoning study and (e) 18 January 2013 for the scalds study. Recruitment of controls commenced with recruitment of the first case to each study and controls were recruited within 4 months of recruitment of cases.

Participants

Cases were children aged 0–4 years with:

1. a fall from furniture

2. a fall on one level

3. a stair fall

4. a poisoning or suspected poisoning from a medicinal or other household product or

5. a scald, resulting in hospital admission or ED or MIU attendance.

Injuries had to have occurred at the address at which the child was registered with a general practitioner (GP) (hereafter referred to as the child’s home). Intentional and fatal injuries were excluded, as were children living in residential care. Cases were eligible to be recruited only once to the study.

We used two sources of controls; community controls and hospital controls. For clarity and simplicity the findings relating to community controls (hereafter referred to as controls) are presented in the main text of the report. Findings relating to hospital controls are summarised in Appendix 1. Children living in residential care were excluded. Controls were children aged 0–4 years without a medically attended injury of the same mechanism as the case on the date of the case’s injury. Controls were eligible to be recruited as a case or as a further control if their second recruitment occurred at least 12 months after their first recruitment. They were not eligible to be recruited more than twice to the study. We aimed to recruit an average of four controls per case, individually matched on age (within 4 months of age of case), sex and calendar time (within 4 months of case injury). To increase the study power and make the most efficient use of controls, when we recruited more than four controls per case (or when cases were later excluded), the extra controls were eligible to be matched to other cases who did not have four matched controls. These were matched on age (within 4 months of age of case), sex and calendar time (within 4 months of the case injury) and study centre, and were eligible to be used only once as an extra matched control.

The eligibility of putative cases to take part in the study was assessed from medical records by clinical staff prior to study invitations being issued. Research staff also assessed eligibility on receipt of completed study questionnaires. Potentially eligible cases were approached by clinical staff face to face during their medical attendance or by telephone or post within 72 hours of their attendance. Controls were recruited by post by general practice or primary care trust (PCT) staff, from the practice register of the case’s GP or, when the case’s practice was unable to participate, from that of a neighbouring practice. To minimise age differences between cases and controls resulting from the time taken to recruit practices and then recruit controls, study invites were sent to children born up to 4 months before and 2 months after the case’s date of birth. Ten children were invited to participate for each case. One reminder was sent to case and control non-respondents 2 weeks after the original mailing.

Variables

Bias

We used several strategies to try to minimise bias. We aimed to minimise recall bias by inviting cases to participate in the study within 72 hours of the injury attendance and measured exposures over a short time period prior to the injury attendance (ranging from 24 hours to 1 week); for controls we measured exposures over the same time period prior to completing the study questionnaire. When possible, we validated the accuracy of self-reported exposures in cases and controls by home observations. To minimise non-response bias, we used methods shown in systematic reviews to increase response rates, including providing a small monetary incentive (£5) for the return of completed questionnaires, using personalised letters, sending mail by first class post, providing Freepost reply envelopes, using reminders including the provision of further questionnaires, keeping the questionnaire as short as possible and using university logos on study documentation. 69,70

Study size

Quantitative variables

All exposures were categorical variables. For confounders measured on a continuous scale, we assessed the linearity of their relationship with outcome measures by adding higher-order terms to regression models and tested significance using likelihood ratio tests with a p-value of < 0.05 taken as significant. When the relationship between age and the outcome of interest was non-linear we grouped age into the three age groups consistent with the age groups for which we had developed age-specific questionnaires (0–12 months, 13–36 months, ≥ 37 months). When other relationships were non-linear, we examined distributions of the confounders and grouped values based on cut-off points that separated the distribution into groups of similar values while ensuring sufficient numbers in each group for analysis. When standard groupings had been used in previous research, for example quintiles of deprivation scores, we grouped values similarly to allow comparisons with previous research. The cut-off points for groupings are given in the results tables.

We devised a score representing parents’ perceptions of their child’s ability to climb by combining responses across eight questions asking about perceptions of ability to climb or reach a range of hazards. Each question had a three-point Likert scale response from ‘not likely’ to ‘very likely’, with a ‘don’t know’ option. The score was created by categorising responses into (1) all not likely, (2) at least one quite likely but none very likely and (3) at least one very likely. Those with missing or ‘don’t know’ responses to individual items were categorised as missing an overall score unless respondents had at least one ‘very likely’ response. We also devised a composite categorical variable describing parents’ perceptions of their stair characteristics by combining responses across seven questions with a three-point Likert response from ‘agree’ to ‘disagree’ (stairs too steep, stairs too narrow, stairs poorly lit, steps in need of repair, banister/handrail in need of repair, stair covering in need of repair and stairs being safe to use). The categories of the composite variable were ‘unsafe’ (answered agree to any of the first six questions or disagree to last question), ‘moderately safe’ (answered combinations of agree, disagree and neither agree nor disagree) and ‘safe’ (answered disagree to all first six questions and agree to last question). Those with missing responses to individual items were categorised as missing a response on the composite variable unless they agreed with any of the first six questions or disagreed with the last question.

When the relationship between distance from hospital and the outcome of interest was non-linear, distance was grouped into quintiles. When the relationship between IMD and the outcome of interest was non-linear IMD was grouped into quintiles.

We used the treatment received as a proxy for injury severity. We created two categories: those who were seen and examined but who did not require any treatment and those requiring treatment in the ED, admitted to hospital or discharged with outpatient or primary care follow-up. We chose these groupings based on the number of cases in each group and combined hospital admissions, those treated in the ED and those discharged with outpatient or primary care follow-up as the numbers admitted to hospital and discharged with outpatient or primary care follow-up were small.

Statistical methods

We calculated kappa coefficients, sensitivities, specificities and predictive values (and 95% CIs) comparing each reported exposure with the observed exposure, with observations used as the ‘gold standard’.

Characteristics of cases and controls have been described using frequencies and percentages for categorical variables and means [standard deviations (SDs)] or medians [interquartile ranges (IQRs)] for continuous variables dependent on their distributions. Conditional logistic regression was used to estimate unadjusted ORs and AORs and 95% CIs for the matched analysis. Analyses were adjusted for area-level deprivation65 and distance from hospital and for confounders identified from DAGs. We developed separate DAGs for each exposure–outcome analysis. All variables that we considered as potential confounders were included in the DAG, and we used Dagitty software [see www.dagitty.net/ (accessed 2 October 2016)] to create a causal diagram for each exposure–outcome analysis and to identify the minimum adjustment set of variables. The regression model for each analysis was adjusted for the variables belonging to the minimum adjustment set for that exposure–outcome analysis by entering them on one step into the model. They were retained in the model regardless of statistical significance or effect on the OR for the exposure. Potential differential effects by child age, sex, ethnicity, single parenthood, housing tenure and unemployment were assessed by adding interaction terms to models. Significance was assessed using likelihood ratio tests with a p-value of < 0.01 taken as significant. When significant interactions were found, the results are presented stratified by socioeconomic variables. Differential effects by injury severity were assessed by stratifying analyses into those who were seen and examined but who did not require any further treatment and those who received treatment or who were admitted to hospital. For the unmatched analyses using hospital controls, unconditional logistic regression was used to estimate unadjusted ORs and AORs and 95% CIs. Analyses were adjusted for age, sex, area-level deprivation65 and distance from hospital, in addition to other confounders identified from DAGs. The population attributable fraction (PAF) per cent was calculated for exposures with statistically significantly raised AORs using a published formula. 73

We followed standard guidance on missing data for the PedsQL score and did not compute mean scale scores when > 50% of the individual scale score responses were missing. When > 50% of questions were answered, mean scale scores were generated with imputation of missing values using the mean of the answered questions. 74 For the HADS score we imputed single missing item values for each subscale using the mean of the remaining six items. When more than one item was missing, subscale scores were not computed. 75 The IBQ, ECBQ and CBQ allowed missing values and were scored as the total score divided by the number of questions answered. 76 We were unable to find guidance for dealing with missing values for the PDH scale so we used the same approach as for the HADS. The main analyses are complete-case analyses, excluding cases and controls with missing data for the exposure or confounding variables. Complete-case analysis gives unbiased estimates when people with missing data are a completely random subset of the individuals in a particular study; the missing data are then called missing completely at random. If, however, missingness is related to other observed or participant data, for example age or sex, this is called missing at random. We undertook multiple imputation, which assumes that missing data are missing at random, to create 20 imputed data sets. These were combined using Rubin’s rules. 77 The multiple imputation models included all sociodemographic characteristics, exposures and confounding variables considered in the analysis models, along with case–control status. The imputation models included interaction terms identified in the complete-case analyses when possible, but in some cases the imputation models would not converge when interaction terms were included so these were omitted. When exposures had > 5% of ‘not applicable’ responses, analyses were repeated coding these as a separate category.

For the validation of exposure measures, to assess whether differences between reported and observed practices may have arisen because of changes made to the home by families after completing questionnaires, we incorporated any changes made in the last 3 months as reported at the home visit to derive a modified value for each exposure. For any cell within the tables comparing reported and observed values, when the percentage of people reporting a change in the previous 3 months was > 20%, the numbers were adjusted to accommodate an assumed change from ‘yes’ to ‘no’ and vice versa, and positive predictive values (PPVs) and negative predictive values (NPVs) were recalculated.

Ethics

Approval for the case–control studies and the validation of exposures study was granted by Nottingham Research Ethics Committee 1 (reference number 09/H0407/14).

Validation of exposures study (study B)

The process of recruitment to study B is shown in Figure 2. In total, 113 cases and 119 controls were contacted by the research team, of whom 81 (72%) and 81 (68%), respectively, received a home visit. This represents 3% of cases and 1% of controls eligible for study A. The period of time between receipt of questionnaire and the visit being carried out varied between 1 and 92 days, with a median of 29 days.

FIGURE 2.

Recruitment to the validation of exposures study (study B). a, Includes eight cases subsequently found not to be eligible for study A (study C, n = 7; study G, n = 1). These eight were not used to compare characteristics of participants in study B. b, Includes 37 controls subsequently found not to be eligible for study A.

Table 1 shows the characteristics of families participating in the home observations and those returning completed questionnaires who were eligible to participate in any of the five case–control studies but who did not have a home observation. For most characteristics, there was no significant difference between families who participated and those who did not. Families for whom the questionnaire respondent was female or the participating child was male were more likely to participate; this was also the case for single-parent families or households with more adults out of work.

Table 2 shows the sensitivities, specificities and predictive values for exposures related to falls. NPVs were high (≥ 70%) for all 12 exposures relating to risk of falls. However, the PPV was ≥ 70% for only five of the fall exposures: safety gates at the top of the stairs; safety gates at the bottom of the stairs; use of safety gates elsewhere in the house; carpeted stairs; and the presence of a landing half-way up the stairs. The sensitivity for eight of the exposures was ≥ 70%. Exposures for which the sensitivity was < 70% were the presence of safety gates other than on the stairs and use of baby walkers, use of stationary play centres and use of travel cots as play pens. The specificity was ≥ 70% for 10 of the 12 exposures, being below this for banisters on stairs and handrails on stairs. Kappa coefficients ranged from 0.2 for use of baby walkers (slight agreement)79 to 0.74 for carpeted stairs (substantial agreement). 79 There was no significant difference [t = 1.77, degrees of freedom (df) = 1.42, p = 0.08] in measured stair steepness (stair height-to-depth ratio) between those reporting that their stairs were too steep (n = 23; mean 0.87, SD 0.21) and those not reporting that their stairs were too steep (n = 121; mean 0.82, SD 0.09). Observed banister gaps were significantly larger than reported gaps (n = 55; Z = 3.12, p = 0.002). The median reported gap was 3.0 inches (IQR 2.0–4.0 inches) whereas the median observed gap was 3.8 inches (IQR 3.5–4.3 inches).

Table 3 shows the sensitivities, specificities, predictive values and percentage agreement for 16 exposures relating to poisoning. All PPVs were low, the highest being 68% for all medicines having CRCs or blister packs. For 11 of the exposures, the NPV was > 70%, whereas sensitivity was > 70% for eight exposures. Kappa coefficients varied from –0.03 for all medicines stored in locked cupboard, cabinet, drawer or fridge (poor agreement)79 to 0.54 for medicines kept in fridge (moderate agreement). 79

Table 4 shows the sensitivities, specificities, predictive values and percentage agreement for exposures relating to scalds. Sensitivity was > 70% for all three scald-related exposures. The PPV was high for two exposures (a kettle with a curly flex and kettle kept at the back of the kitchen surface), whereas the NPV was high for having a safety gate across the kitchen doorway and for having a kettle kept at the back of the kitchen surface. Kappa coefficients ranged from 0.13 (slight agreement) to 0.57 (moderate agreement). 79

Over-reporting of safety practices was more common than under-reporting. We were able to calculate predictive values for 30 safety practices and found that, for 24 of these, more families over-reported than under-reported (NPV exceeds PPV) and, for the remaining six practices, more families under-reported than over-reported (PPV exceeds NPV).

We explored whether or not differences between reported and observed safety practices could be accounted for by families changing safety practices between completing the questionnaire and the home observation. This did not appear to explain the differences between reported and observed practices, as the findings were similar to those from the main analysis when using the adjusted figures. 78 The results are available from the authors on request.

Associations between observations and self-reports differed significantly between cases and controls for only one exposure, which was storage of household products in containers that were different from the ones in which they came (χ² = 4.91, p = 0.03). The results are available from the authors on request.

Case–control study of risk and protective factors for falls from furniture (study A)

A total of 672 cases and 2648 controls participated in the study. The process of recruitment to the study is shown in Figure 3. In total, 35% of cases and 33% of controls agreed to participate. The age and sex of participants and non-participants in the falls from furniture study were similar, as shown in Table 5.

FIGURE 3.

Flow of cases and controls through the falls from furniture study: (a) recruitment of cases; and (b) recruitment of controls. a, Assumed to be 10 times the number of cases as practices were asked to invite 10 controls for each case; b, controls for cases from the falls from furniture study for whom there were more than four controls and controls for fall from furniture cases who were not matched to the case (e.g. because the case was excluded); c, controls for cases from the other four ongoing case–control studies. Reproduced with permission of JAMA Pediatrics 2015;169(2):145–153. 80 Copyright 2015 American Medical Association.

The mean number of controls per case was 3.94. The median time from date of injury to date of questionnaire completion for cases was 10 days (IQR 6–20 days).

Most cases sustained single injuries (86%), most commonly a bang on the head (59%), cuts/grazes not requiring stitches (19%) and fractures (14%). Most cases (60%) were seen and examined but did not require treatment, with 29% treated in the ED, 4% were admitted to hospital and 7% treated and discharged with a follow-up appointment.

Table 6 shows the sociodemographic characteristics of cases and controls. As expected, because controls were recruited after the matched cases, they were slightly older than cases (median age 1.91 vs. 1.74 years). Cases were slightly more likely than controls to live in a household with no adults in paid work (17.7% vs. 12.6%), in a household receiving state benefits (43.0% vs. 35.9%) and in non-owner-occupied housing (39.5% vs. 32.2%).

Table 7 shows the frequency of exposures among cases and controls and unadjusted ORs, and Table 8 shows ORs adjusted for a range of confounding variables. Adjusting for confounders had relatively little impact on most ORs; only one out of 13 ORs changed by > 10% after adjustment (had things child could climb on to reach high surfaces – OR 0.85, AOR 0.94). Compared with parents of controls, in the adjusted analyses parents of cases were more likely not to use a safety gate (AOR 1.65, 95% CI 1.29 to 2.12; PAF 15%), more likely to leave children on raised surfaces (AOR 1.66, 95% CI 1.34 to 2.06, PAF 23%) and more likely not to have taught their children rules about climbing on objects in the kitchen (AOR 1.58, 95% CI 1.16 to 2.15, PAF 16%) and their children were less likely to climb or play on garden furniture (AOR 0.74, 95% CI 0.56 to 0.97). Most of the ORs for the remaining nine exposures were close to 1, with seven being > 1 (ranging from 1.01 to 1.35) and two being < 1 (0.77 and 0.94). All had CIs indicating that associations could have occurred by chance.

There were significant interactions with child age. ORs for each age group are shown in Table 9. Comparing cases to controls, for children aged 0–12 months, parents of cases were more likely to leave children on raised surfaces (AOR 5.62, 95% CI 3.62 to 8.72; PAF 50%), change nappies on raised surfaces (AOR 1.89, 95% CI 1.24 to 2.88; PAF 34%) and put children in car/bouncing seats on raised surfaces (AOR 2.05, 95% CI 1.29 to 3.27; PAF 12%) than parents of controls. In the 13–36 month age group, parents of cases were less likely to put car or bouncing seats on raised surfaces than controls (AOR 0.22, 95% CI 0.05 to 0.94). The effect for children climbing or playing on furniture was only significant in children aged 3 years and older, with cases being more likely to climb or play on furniture (AOR 9.25, 95% CI 1.22 to 70.07; PAF 88%) than controls.

Tables showing the results of the following sensitivity analyses are available from the authors on request. None of the AORs using the multiply imputed data differed by > 10% from those using the complete-case data for the main analysis. Five of the AORs for the interaction analyses differed by > 10% between the analysis using the multiply imputed data and the analysis using the complete-case data. All six exposures with a ‘not applicable’ response option had > 5% of ‘not applicable’ responses. Analyses were undertaken incorporating a separate category for ‘not applicable’ responses. None of the AORs for the six exposures differed by > 10% between the analyses with and the analyses without the ‘not applicable’ category.

Stratifying analyses by the treatment received (as a proxy for injury severity) resulted in AORs with fairly broad and overlapping 95% CIs for those seen and examined in the ED and those admitted/treated in the ED/discharged with follow-up for all exposures. The results from these analyses are available from the authors on request.

Case–control study of risk and protective factors for falls on one level (study A)

A total of 582 cases and 2460 controls participated in the falls on one level study. The process of recruitment to the study is shown in Figure 4. In total, 24% of cases and 24% of controls agreed to participate and were included in the analysis. Table 10 shows that participants and non-participants were similar in terms of sex and age.

FIGURE 4.

Flow of cases and controls through the falls on one level study: (a) recruitment of cases; and (b) recruitment of controls. a, Assumed to be 10 times the number of cases as practices were asked to invite 10 controls for each case; b, controls for cases from the other four ongoing case–control studies; c, controls for cases from the falls on one level study who had more than four controls and controls for falls on one level cases who were not matched to the case (e.g. because the case was excluded). Reproduced with permission from Benford P, Young B, Coupland C, Watson M, Hindmarch P, Hayes M, Goodenough T, Majsak-Newman G, Kendrick D. Risk and protective factors for falls on one level in young children: multicentre case–control study. Injury Prevention 2015;21:381–8. 81 Copyright © 2015 BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health. All rights reserved.

The mean number of controls per case was 4.23. The median time from date of injury to date of questionnaire completion for cases was 10 days (IQR 6–20 days).

The majority of cases had sustained single injuries (80%), most commonly a bang on the head (52%), cuts/grazes not requiring stitches (29%) and cuts needing stitches (17%). In total, 47% of cases were seen and examined but did not require treatment, 46% were treated in the ED, 3% were admitted to hospital and 4% were treated and discharged with a follow-up appointment.

Table 11 shows the sociodemographic characteristics of cases and controls. Controls were slightly older than cases (median age 2.16 vs. 2.08 years). Cases were slightly more likely than controls to have a mother who was aged ≤ 19 years when she had her first child (16.5% vs. 10.8%), to live in a household with no adults in paid work (19.1% vs. 12.4%), to live in a household receiving state benefits (44.3% vs. 37.0%) and to live in non-owner-occupied housing (42.5% vs. 32.7%).

Table 12 shows the frequency of exposures among cases and controls and unadjusted ORs, and Table 13 shows ORs adjusted for a range of confounding variables. Adjusting for confounders had relatively little impact on most ORs. Four out of 13 ORs changed by > 10% on adjustment (having tripping hazards on floors: OR 0.88, AOR 1.07; not using safety gate to prevent access to garden: OR 0.58, AOR 1.01; unsupervised playing in garden: OR 0.76, AOR 0.89; not using a playpen/travel cot: OR 0.76, AOR 0.90). Compared with parents of controls, in the adjusted analyses parents of cases were less likely not to use furniture corner covers (AOR 0.72, 95% CI 0.54 to 0.94) and less likely to have rugs/carpets not firmly fixed to the floor (AOR 0.77, 95% CI 0.59 to 0.99). ORs for most of the remaining 11 exposures were close to 1, with five being > 1 (ranging from 1.01 to 1.37) and six being < 1 (ranging from 0.73 to 0.97). All had CIs indicating that associations could have occurred by chance.

There was a significant interaction between the number of adults living with the child and rugs/carpets not being firmly fixed to the floor. ORs for each category are shown in Table 14. In households where the child lived with one parent, rugs/carpets were more likely not to be fixed firmly to the floor in cases than in controls (AOR 2.54, 95% CI 1.16 to 5.54, PAF 18%), whereas in households where the child lived with more than one adult they were less likely not to be fixed firmly to the floor in cases than in controls (AOR 0.69, 95% CI 0.52 to 0.90).

Tables showing the results of the following sensitivity analyses are available from the authors on request. Two of the AORs using the multiply imputed data differed by > 10% from those using the complete-case data for the main analysis (did not use safety gate to prevent access to garden: multiply imputed AOR 0.78, 95% CI 0.50 to 1.21; complete case AOR 1.01, 95% CI 0.58 to 1.74; not taught rules about running in the house: multiply imputed AOR 0.82, 95% CI 0.64 to 1.06; complete case AOR 0.73, 95% CI 0.54 to 1.00). One of the AORs for the interaction analyses differed by > 10% between analyses using the multiply imputed data and analyses using the complete-case data.

Three exposures with a ‘not applicable’ response option had > 5% of ‘not applicable’ responses. Analyses were undertaken incorporating a separate category for ‘not applicable’ responses. One of the AORs for the three exposures differed by > 10% between the analyses with and the analyses without the ‘not applicable’ category (did not use safety gate to prevent access to the garden: AOR with ‘not applicable’ category 1.01, 95% CI 0.58 to 1.74; AOR without ‘not applicable’ category 0.89, 95% CI 0.54 to 1.48).

Stratifying analyses by the treatment received (as a proxy for injury severity) resulted in AORs with fairly broad and overlapping 95% CIs for those seen and examined in the ED and those admitted/treated in the ED/discharged with follow-up for all exposures. The results from these analyses are available from the authors on request.

Case–control study of risk and protective factors for stair falls (study A)

A total of 610 cases and 2658 controls participated in the stair falls study. The process of recruitment to the study is shown in Figure 5. In total, 33% of cases and 29% of controls agreed to participate and were included in the analysis. Table 15 shows that participants and non-participants were similar in terms of sex, but a higher proportion of participants than non-participants were aged 0–12 months (19.0% vs. 12.3%).

FIGURE 5.

Flow of cases and controls through the stair falls study: (a) recruitment of cases; and (b) recruitment of controls. a, Assumed to be 10 times the number of cases as practices were asked to invite 10 controls for each case; b, controls for cases from the fall from stair falls study who had more than four controls and controls for stair falls cases who were not matched to the case (e.g. because the case was excluded); c, controls for cases from the other four ongoing case–control studies. Kendrick D, Zou K, Ablewhite J, Watson M, Coupland C, Bryony K, Hawkins A, Reading R. Risk and protective factors for falls on stairs in young children: multicentre case–control study. Archives of Disease in Childhood 2016;101:909–16. 82 Copyright © 2016 BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health. All rights reserved.

The mean number of controls per case was 4.36. The median time from date of injury to date of questionnaire completion for cases was 11 days (IQR 7–21 days).

The majority of cases had sustained single injuries (85%), most commonly a bang on the head (66%), cuts/grazes not requiring stitches (14%) and broken bones (12%). Most cases (64%) were seen and examined but did not require treatment, 25% were treated in the ED, 5% were admitted to hospital and 6% were treated and discharged with a follow-up appointment.

Table 16 shows the sociodemographic characteristics of cases and controls. Compared with controls, cases were less likely to live in a household with more than one adult in paid work (50.0% vs. 59.0%). They also lived in areas with higher levels of deprivation (median IMD score 18.7 vs. 15.2), were more likely to have a mother who had had her first child aged ≤ 19 years (18.5% vs. 9.1%) and were more likely to live in a single adult household (14.6% vs. 10.5%), a household in receipt of state benefits (40.9% vs. 32.4%), in non-owner-occupied housing (40.4% vs. 32.2%) or in a household without a car (14.7% vs. 9.7%).

Table 17 shows the frequency of exposures among cases and controls and unadjusted ORs and Table 18 shows ORs adjusted for a range of confounding variables. Ten of the 24 ORs changed by > 10% on adjustment, with all reducing in magnitude (no carpet on stairs: OR 1.91, AOR 1.52; stairs too steep: OR 1.35, AOR 1.21; stairs too narrow: OR 1.35, AOR 1.28; stairs need repair: OR 1.97, AOR 1.71; stair covering needs repair: OR 1.74, AOR 1.41; stairs not safe: OR 1.71, AOR 1.46; no banisters: OR 1.44, AOR 1.27; not taught child rules about going downstairs: OR 1.60, AOR 1.36; not taught child rules about leaving things on stairs: OR 1.00, AOR 0.85; banister width 2.5–3.75 inches: OR 0.84, AOR 0.75).

Compared with parents of controls, in the adjusted analysis parents of cases were more likely not to use safety gates on their stairs (AOR 2.50, 95% CI 1.90 to 3.29; PAF 21%) or to leave the gates open (AOR 3.09, 95% CI 2.39 to 4.00; PAF 24%), not to have carpeted stairs (AOR 1.52, 95% CI 1.09 to 2.10; PAF 5%) and not to have a landing part-way up their stairs (AOR 1.34, 95% CI 1.08 to 1.65; PAF 18%). They were also more likely to consider their stairs not safe to use (AOR 1.46, 95% CI 1.07 to 1.99; PAF 5%) or their steps in need of repair (AOR 1.71, 95% CI 1.16 to 2.50; PAF 5%). Case households were less likely than control households to have tripping hazards on their stairs (AOR 0.77, 95% CI 0.62 to 0.97) or to not have handrails on all stairs (AOR 0.69, 95% CI 0.56 to 0.86). ORs for most of the remaining 16 exposures were close to 1, with 11 being > 1 (ranging from 1.07 to 1.41) and five being < 1 (ranging from 0.69 to 0.97). All had CIs indicating that associations could have occurred by chance.

Table 19 shows significant interactions in the adjusted analysis. Comparing cases with controls, parents of cases aged 0–12 months and 13–36 months were more likely to have left safety gates on stairs open than closed, with a particularly high OR in parents with infants (AOR 0–12 months 8.64, 95% CI 3.99 to 18.68, PAF 46%; AOR 13–36 months 2.64, 95% CI 1.92 to 3.64, PAF 24%). Parents of cases in all age groups were more likely not to have a safety gate on stairs than to have a closed gate and the OR was again higher in parents with infants (AOR 0–12 months 3.27, 95% CI 1.48 to 7.20, PAF 18%; AOR 13–36 months 2.33, 95% CI 1.60 to 3.39, PAF 15%; AOR ≥ 37 months 2.08, 95% CI 1.23 to 3.51, PAF 32%). The association between safety gates and stair falls varied by baby walker use, with a particularly high OR for leaving a safety gate open compared with having a closed gate in walker users (AOR walker users 7.37, 95% CI 4.36 to 12.45, PAF 44%). Parents of cases in households in which no adults were in paid work were less likely not to have taught children rules about carrying things downstairs (AOR 0.44, 95% CI 0.20 to 0.96) or not to have taught children rules about leaving things on stairs (AOR 0.27, 95% CI 0.12 to 0.60). Parents of cases in single adult households were more likely not to have carpeted stairs (AOR 11.07, 95% CI 3.89 to 31.53, PAF 26%) and were less likely not to have taught children rules about leaving things on stairs (AOR 0.33, 95% CI 0.15 to 0.75).

Tables showing the results of the following sensitivity analyses are available from the authors on request. In the analysis using community controls, the AORs for four exposures using the multiply imputed data differed by > 10% from those using the complete-case data for the main analysis. These were not having carpeted stairs (multiply imputed AOR 1.68, 95% CI 1.25 to 2.25; complete case AOR 1.52, 95% CI 1.09 to 2.10), having a stair carpet in need of repair (multiply imputed AOR 1.57, 95% CI 1.13 to 2.18; complete case AOR 1.41, 95% CI 0.99 to 2.03), not using a stationary activity centre (multiply imputed AOR 0.96, 95% CI 0.75 to 1.24; complete case AOR 1.08, 95% CI 0.80 to 1.46) and banister width (2.5–3.75 inches: multiply imputed AOR 0.85, 95% CI 0.61 to 1.20; complete case AOR 0.83, 95% CI 0.53 to 1.29; > 3.75 inches: multiply imputed AOR 0.90, 95% CI 0.65 to 1.25; complete case AOR 0.75, 95% CI 0.48 to 1.18). Four of the interactions from the complete-case analysis remained significant at the 1% level in the multiply imputed analysis and two [interactions between (1) teaching children rules about leaving things on stairs and single parent households and (2) teaching children rules about carrying things on stairs and parental unemployment] had p-values of 0.011 in the multiply imputed analysis. Patterns of risk were similar for the multiply imputed and complete-case analyses, but AORs differed by > 10% between the complete-case analyses and the multiply imputed analyses for 12 out of 20 AORs. Stratifying analyses by the treatment received (as a proxy for injury severity) resulted in AORs with fairly broad and overlapping 95% CIs for the seen and examined in the ED and the admitted/treated in the ED/discharged with follow-up groups for all exposures. The results from these analyses are available from the authors on request.

Case–control study of risk and protective factors for poisonings (study A)

A total of 567 cases and 2320 controls participated in the poisonings study. The process of recruitment to the study is shown in Figure 6. In total, 28% of cases and 28% of controls agreed to participate and were included in the analysis. The age and sex of participants and non-participants in the poisonings study were similar, as shown in Table 20.

FIGURE 6.

Flow of cases and controls through the poisonings study: (a) recruitment of cases; and (b) recruitment of controls. a, The study the participant had previously been recruited to was not recorded; b, includes eight participants previously recruited to one of the other ongoing CC studies as a case and five previously recruited to this study as a control > 12 months previously; c, assumed to be ten times the number of cases as practices were asked to invite 10 controls for each case; d, community controls for cases from the other four ongoing case–control studies; e, controls for cases from poisoning study that had more than four controls; f, includes nine participants previously recruited to one of the other ongoing CC studies as a control and one participant previously recruited to this study as a control > 12 months previously. Reproduced with permission from Kendrick D, Majsak-Newman G, Benford P, Coupland C, Timblin C, Hayes M, et al. Poison prevention practices and medically attended poisoning in young children: multicentre case–control study. Injury Prevention 2016; in press. 83 © 2017 by the BMJ Publishing group Ltd. All rights reserved.

The mean number of controls per case was 4.09. The median time from date of injury to date of questionnaire completion for cases was 12 days (IQR 6–22 days).

The majority of cases had sustained single injuries. Parents of seven cases reported injuries in addition to poisonings. Most cases (84%) were seen and examined but did not require treatment, 6% were treated in the ED, 8% were admitted to hospital and 2% were treated and discharged with a follow-up appointment.

Table 21 shows the sociodemographic characteristics of cases and controls.

Table 22 shows the frequency of exposures among cases and controls and unadjusted ORs, and Table 23 shows ORs adjusted for a range of confounding variables. Four of the eighteen ORs changed by > 10% on adjustment (medicines transferred into different container: OR 1.15, AOR 0.96; household products not stored at adult eye level or above: OR 0.84, AOR 0.95; household products transferred into different containers: OR 1.74, AOR 1.20; no safety gate to stop access to kitchen: OR 0.91, AOR 1.05).

Compared with parents of controls, in the adjusted analyses parents of cases were more likely not to store all medicines at adult eye level or above (AOR 1.59, 95% CI 1.21 to 2.09; PAF 15%) and were more likely not to store all medicines safely (locked away or at adult eye level or above) (AOR 1.83, 95% CI 1.38 to 2.42; PAF 16%). Parents of cases were less likely than parents of controls not to store all household products safely (locked away or at adult eye level or above) (AOR 0.77, 95% CI 0.59 to 0.99). They were also more likely not to put medicines away immediately after use (AOR 2.11, 95% CI 1.54 to 2.90; PAF 20%) or to put household products away immediately (AOR 1.79, 95% CI 1.29 to 2.48;, PAF 11%) and less likely not to have taught their children what to do or not do if medicines were left on the worktop (AOR 0.66, 95% CI 0.45 to 0.96). ORs for the remaining 12 exposures were close to 1, with four being > 1 (ranging from 1.05 to 1.25), and eight being < 1 (ranging from 0.81 to 0.96). All had CIs indicating that associations could have occurred by chance.

Table 24 shows significant interactions in the adjusted analysis comparing cases with controls. Parents of cases living in single adult households were more likely not to store all household products at adult eye level or above (AOR 2.43, 95% CI 1.09 to 5.43; PAF 50%). Parents of female cases were less likely not to keep all medicines locked away (AOR 0.59, 95% CI 0.37 to 0.94).

Tables showing the results of the following sensitivity analyses are available from the authors on request. In the analysis using community controls, four of the AORs using the multiply imputed data differed by > 10% from those using the complete-case data for the main analysis. These were medicines not stored safely (multiply imputed AOR 1.62, 95% CI 1.29 to 2.05; complete case AOR 1.83, 95% CI 1.38 to 2.42), household/cleaning products not stored safety (multiply imputed AOR 0.91, 95% CI 0.73 to 1.13; complete case AOR 0.77, 95% CI 0.59 to 0.99), transferring cleaning products to different containers (multiply imputed AOR 1.47, 95% CI 0.80 to 2.69; complete case AOR 1.20, 95% CI 0.54 to 2.65) and not putting household/cleaning products away immediately after use (multiply imputed AOR 1.61, 95% CI 1.26 to 2.05; complete case AOR 1.79, 95% CI 1.29 to 2.48). Two of the AORs differed by > 10% between the multiply imputed and the complete-case interaction analyses.

One exposure with a ‘not applicable’ response option had > 5% of ‘not applicable’ responses. Analyses were undertaken incorporating a separate category for ‘not applicable’ responses. The AORs did not differ by > 10% between analyses with and analyses without the ‘not applicable’ category. The results from these analyses are available from the authors on request. Stratifying analyses by the treatment received (as a proxy for injury severity) resulted in AORs with fairly broad and overlapping 95% CIs for those seen and examined in the ED and those admitted/treated in the ED/discharged with follow-up for all exposures. The results from these analyses are available from the authors on request.

Case–control study of risk and protective factors for scalds (study A)

A total of 338 cases and 1438 controls participated in the scalds study. The process of recruitment to the study is shown in Figure 7. In total, 32% of cases and 29% of controls agreed to participate and were included in the analysis. The age and sex of participants and non-participants in the scalds study were similar, as shown in Table 25.

FIGURE 7.

Flow of cases and controls through the scalds study: (a) recruitment of cases; and (b) recruitment of controls. a, Assumed to be ten times the number of cases as practices were asked to invite 10 controls for each case; b, controls for cases from the other four ongoing case–control studies; c, controls for cases from scald study that had more than four controls and controls for scald cases that were not matched to the case (e.g. because case was excluded).

The mean number of controls per case was 4.25. The median time from date of injury to date of questionnaire completion for cases was 11 days (IQR 6–21 days).

All cases had sustained a scald and no other injury in addition to the scald. In total, 31% received treatment at the ED, 24% were seen and examined but did not require treatment, 18% were admitted to hospital and 27% were treated and discharged with a follow-up appointment.

Table 26 shows the sociodemographic characteristics of cases and controls. Controls were slightly older than cases (median age 1.56 vs. 1.47 years). Cases were less likely to be of white ethnic origin (81.8% vs. 91.3%) and more likely to have only one child under the age of 5 years (67.5% vs. 62.3%), live in an overcrowded household (15.2% vs. 8.6%) or live in a rented home (49.6% vs. 37.1%). Case households were more likely to receive state benefits than control households (46.0% vs. 35.0%). Cases lived in areas of higher social deprivation (median IMD score 20.6 vs. 15.7) and typically spent less time being cared for outside the home (median number of hours per week 5.5 vs. 12). Parental perception of their child’s ability to climb was lower for cases: 78.6% of case parents thought that it was very likely that their child could climb to at least one of the eight places described on the questionnaire compared with 82.8% of control parents.

Table 27 shows the frequency of exposures among cases and controls and unadjusted ORs and Table 28 shows ORs adjusted for a range of confounding variables. Fifteen of the 28 ORs changed by > 10% after adjustment (no safety gate: OR 1.79, AOR 1.46; things that could be climbed on to reach high surfaces: OR 1.07, AOR 1.24; kettle not at back of worktop/cooker: OR 1.46, AOR 1.20; water temperature too hot: OR 0.67, AOR 0.96; water temperature not known or > 54°C: OR 1.29, AOR 0.99; played/climbed on furniture: OR 0.54, AOR 0.62; held by someone holding hot drink: OR 0.95, AOR 0.83; hot drinks in reach of child: OR 1.99, AOR 2.33; pan handles not turned to back of cooker: OR 1.26, AOR 0.91; child left alone in bathroom: OR 0.53, AOR 0.70; bath run by older child: OR 1.13, AOR 0.74; older child supervised child in bath: OR 0.82, AOR 1.10; not taught rules about bathtubs: OR 2.16, AOR 1.42; not using playpen/travel cot: OR 1.16, AOR 1.33; not using stationary activity centre: OR 1.62, AOR 1.22).

Compared with parents of controls, in the adjusted analysis parents of cases were more likely to have not taught their child rules about things not to climb on in the kitchen (AOR 1.66, 95% CI 1.12 to 2.47; PAF 20%), what to do or not do when parents are cooking using the top of the cooker (AOR 1.95, 95% CI 1.33 to 2.85; PAF 26%) and about hot things in the kitchen (AOR 1.89, 95% CI 1.30 to 2.75; PAF 26%). They were also more likely than control parents to have left hot drinks within reach of their child (AOR 2.33, 95% CI 1.63 to 3.31; PAF 31%). Cases were less likely than controls to have played or climbed on furniture (AOR 0.62, 95% CI 0.40 to 0.96) or to have been left alone in the bath (AOR 0.47, 95% CI 0.30 to 0.75). ORs for most of the remaining 22 exposures were close to 1, with 10 being > 1 (ranging from 1.10 to 1.46) and 12 being ≤ 1 (ranging from 0.70 to 1.00). All had CIs indicating that associations could have occurred by chance.

As shown in Table 29, there were three exposures for which there was a significant interaction with one of the sociodemographic variables. Comparing cases with controls, parents in households with two or more adults in paid work were more likely not to have taught their child rules about what to do or not do when in the bathtub (AOR 2.81, 95% CI 1.43 to 5.53; PAF 33%). Compared with parents of controls, in single adult households parents of cases were less likely to have a hot water temperature of ≥ 54 °C (or not know the water temperature) (AOR 0.42, 95% CI 0.07 to 2.72), whereas, in households with two or more adults, parents of cases were more likely to have a hot water temperature of ≥ 54 °C (or not know the water temperature) (AOR 1.47, 95% CI 0.85 to 2.56). Compared with control parents, case parents living in rented accommodation were more likely never to check their child’s bathwater temperature using a thermometer or other gadget (AOR 1.84, 95% CI 1.03 to 3.28, PAF 36%), whereas parents of cases in owner-occupied housing were less likely to never check the bathwater temperature using a thermometer or other gadget (AOR 0.65, 95% CI 0.42 to 1.03).

Tables showing the complete set of results of the following sensitivity analyses are available from the authors on request. Seventeen of the AORs using the multiply imputed data differed by > 10% from those using the complete-case data for the main analysis and these are shown in Table 30. Three of the AORs differed by > 10% between the multiply imputed and the complete-case interaction analyses.

For five exposures, the proportion of ‘not applicable’ responses was > 5%. Analyses were undertaken incorporating a separate category for ‘not applicable’ responses. The AOR differed by > 10% in the analyses comparing cases with controls with and without a ‘not applicable’ category for the bath being run by an older child (AOR with ‘not applicable’ category 0.62, 95% CI 0.28 to 1.34; AOR without ‘not applicable’ category 0.74, 95% CI 0.31 to 1.82) and for older children looking after a younger child in the bath (AOR with ‘not applicable’ category 0.95, 95% CI 0.56 to 1.00; AOR without ‘not applicable’ category 1.10, 95% CI 0.63 to 1.93). The results from these analyses are available from the authors on request.

Stratifying analyses by the treatment received (as a proxy for injury severity) resulted in AORs with fairly broad and overlapping 95% CIs for the seen and examined in the ED and the admitted/treated in the ED/discharged with follow-up groups for almost all exposures. However, the AORs differed between those admitted/treated in the ED/followed up post discharge and those seen and examined in the ED for putting hot drinks or liquids on tables with tablecloths on. Parents of cases who were seen and examined in the ED were less likely than parents of controls to put hot drinks on tables with cloths (AOR 0.11, 95% CI 0.02 to 0.63), but parents of cases admitted to hospital/treated in the ED/followed up post discharge were more likely to put hot drinks on tables with tablecloths than parents of controls (AOR 2.02, 95% CI 1.22 to 3.36). The results from these analyses are available from the authors on request.

Main findings

We found that a range of modifiable risk factors were associated with secondary care-attended falls from furniture, falls on stairs or steps, poisonings and scalds in children aged 0–4 years. Only two modifiable risk factors were associated with secondary care-attended falls on one level in children aged 0–4 years.

Compared with control parents, parents of children who had a fall from furniture were more likely not to use safety gates anywhere in the home (PAF 15%) and, for those with children aged 0–12 months, were more likely to have left them on raised surfaces (PAF 50%), changed nappies on raised surfaces (PAF 34%) and put them in car/bouncing seats on raised surfaces (PAF 12%). Parents of children who had fallen from furniture were less likely to put children aged 13–36 months in car/bouncing seats on raised surfaces (78% reduction in odds). They were more likely not to have taught children rules about things they should not climb on in the kitchen (PAF 16%) and, for those with children aged ≥ 37 months, their children played or climbed on furniture more often (PAF 88%) than control children. Case children who had had a fall from furniture played or climbed on garden furniture less often than control children (26% reduction in odds).

Compared with parents of controls, parents of children who had had a fall on one level were less likely not to use furniture corner covers (28% reduction in odds) and less likely not to have rugs/carpets firmly fixed to the floor (23% reduction in odds). The association with rugs/carpets firmly fixed to the floor varied with the number of adults in the household. Households with one adult in which children had had a fall on one level were more likely not to have rugs/carpets fixed to floors than control households (PAF 18%), whereas households with two adults in which children had had a fall on one level were less likely not to have rugs/carpets fixed to floors than control households (31% reduction in odds).

Compared with parents who kept safety gates closed, parents of children who had fallen down stairs or steps were more likely not to use safety gates on stairs (PAF 21%) or to leave safety gates on stairs open (PAF 24%) than parents of controls. Compared with control households, the odds of not using a safety gate on stairs and of leaving the gate open appeared to be particularly high in families with children aged 0–12 months (PAF 18% and 46%, respectively) and the odds of leaving safety gates open appeared to be high in families who used baby walkers (PAF 44%). Families with children who had fallen down stairs or steps were more likely than controls not to have carpeted stairs (PAF 5%) or not to have a landing part-way up their stairs (PAF 18%). They were also more likely to consider their stairs not safe to use (PAF 5%) or in need of repair (PAF 5%). They were less likely than controls to have tripping hazards on their stairs (23% reduction in odds) or not to have handrails on all stairs (31% reduction in odds). Compared with controls, families with no adults in paid work whose children had fallen down stairs or steps were more likely to have taught children rules about carrying things down stairs and leaving things on stairs (56% and 73% reduction in odds of not teaching rules, respectively). Compared with controls, single adult families whose children had fallen down stairs or steps were more likely to have taught children rules about leaving things on stairs (67% reduction in odds of not teaching rules) and to not have carpeted stairs (PAF 26%).

Compared with parents of controls, parents of children who had had a poisoning were more likely not to store medicines at adult eye level or above (PAF 15%), not to store medicines safely (locked away or at adult eye level or above) (PAF 16%) and not to put medicines (PAF 20%) or household products (PAF 11%) away immediately after use. They were also less likely not to store household products safely (23% reduction in odds) and not to have taught children rules about what to do if medicines are left on the worktop (34% reduction in odds). Parents of children who had had a poisoning in single adult households were more likely than control parents not to store household products at adult eye level or above (PAF 50%). Parents of girls who had had a poisoning were less likely than parents of controls not to lock medicines away (41% reduction in odds).

Compared with parents of controls, parents of children who had had a scald were more likely to have left hot drinks in reach of children (PAF 31%) and more likely not to have taught children rules about climbing in the kitchen (PAF 20%), about what to do or not to do when adults are using the top of the cooker (PAF 26%) or about hot things in the kitchen (PAF 26%). Parents of children who had had a scald were less likely than control parents to have left a child alone in the bath (53% reduction in odds) and their children climbed or played on furniture less often (38% reduction in odds). Compared with controls, families with at least two adults in paid work whose children had had a scald were more likely not to have taught children rules about what to do or not to do when in the bathtub (PAF 33%). Single adult families with children who had had a scald were less likely than controls to report an unsafe or unknown hot water temperature (58% reduction in odds). Compared with parents of controls, parents of children with a scald living in rented accommodation were more likely not to check the bathwater temperature with a thermometer (PAF 36%).

Most exposures were study specific. Not using safety gates (other than on stairs) was an exposure in all five case–control studies and ORs were > 1 for all studies (ranging from 1.05, 95% CI 0.80 to 1.37 for poisonings to 1.65, 95% CI 1.29 to 2.12 for falls from furniture). All case–control studies included exposures related to teaching children safety rules, but only teaching rules about climbing in the kitchen was measured in more than one study, with both studies finding ORs > 1 (falls from furniture OR 1.58, 95% CI 1.16 to 2.15; scalds OR 1.66, 95% CI 1.12 to 2.47). Across all studies, nine of the 13 ORs related to teaching safety rules were > 1 (ranging from 1.13, 95% CI 0.83 to 1.52 for rules about slippery floors and falls on one level to 1.95, 95% CI 1.33 to 2.85 for rules about what to do or not do when parents are using the top of the cooker and scalds).

Strengths and limitations

We report the largest case–control studies to date examining associations between a range of modifiable risk factors for falls, poisoning and scalds. These studies were conducted in NHS hospitals across England, including urban and rural areas. Adjustment was made for a wide range of potential confounding factors using DAGs. For four of our five studies, the majority of ORs using multiply imputed data for the main analysis did not differ by > 10% from those in the complete-case analysis. However, in most studies, a larger number of ORs in the interaction analyses differed by > 10% between the multiple imputation and the complete-case analyses.

Case–control studies have limitations arising from their observational nature. These include, but are not limited to, measurement error, a range of different types of bias and confounding. Each of these are discussed below. We validated measures for exposures when possible and found high (> 70%) sensitivities and specificities for six out of 12 falls exposures, for two out of 15 poisoning exposures and for two out of three scalds exposures. We used home observations as the ‘gold standard’, but it is possible that families may have made changes to their homes either as a result of the injury or in anticipation of the home observation. In addition, there may have been some social desirability bias, with parents reporting responses that they judged to be ‘more acceptable’. These may potentially explain some of the lack of agreement that we found between parent-reported and observed exposures. It is likely that some misclassification of exposures occurred. Misclassification is likely to be lowest when sensitivity and specificity are both high. Sensitivity and specificity were both > 70% for having safety gates on stairs or across kitchen doorways, having carpeted stairs and landings part-way up stairs, having playpens, furniture corner covers and cordless or curly-flexed kettles and storing household products at adult eye level or above. For other exposures, when misclassification is higher it is more likely that ORs are biased towards the null (although this does not always occur86) and this may partly explain our failure to find associations between some exposures and falls, poisonings and scalds. We did explore whether or not the differences between self-reported and observed exposures varied between cases and controls, and we found similar levels of under- and over-reporting for both groups for most exposures. This suggests that differential misclassification is unlikely to have occurred to a large extent. Our analyses did not take misclassification of exposures into account, and for this reason our findings should be interpreted with caution. Future studies should consider adjusting for exposure misclassification.

The participation rates for cases and controls were similar, but were low for all studies, ranging from 24% to 35% for cases and from 24% to 33% for controls across the five studies. If reasons for participation are associated with the exposure or outcome of interest, selection bias may have occurred. Our participation rates do not show large differences by case/control status, age and sex, but we were not able to assess the prevalence of exposures in participants and non-participants, and caution should be exercised in interpreting our findings. In addition to social desirability bias discussed above, recall bias may have occurred. These two types of bias could potentially impact on our ORs in different directions. As most injuries were relatively minor, it is possible that a small number of controls may have had similar injuries to cases and on the same date as the case injury but did not seek medical attention for those injuries. This could lead to misclassification of cases and controls. However, this is likely to apply to only a small number of controls; hence, we would expect this to have at most only a minor impact on our results. If seeking medical attention is associated with exposures of interest, this may lead to overestimation of ORs, but the extent to which this may have introduced bias is difficult to assess.

Most ORs for not teaching children various safety rules were > 1 across the five case–control studies and were significantly raised for rules about climbing in the kitchen for falls from furniture and scalds and for rules about what to do or not do when parents were using the cooker top and about not touching hot things for scalds. It is possible that parents who use safety rules supervise their children differently from parents who do not use rules and, as we were not able to adjust for this, residual confounding may partly explain these findings.

In all five case–control studies, cases were more disadvantaged than controls. Socioeconomic disadvantage is likely to be associated with some of the exposures of interest in our studies and, although we adjusted for a range of confounders, it is possible that some residual confounding remained. It is also possible that families belonging to black and minority ethnic (BME) groups were under-represented in our studies and that for some studies (scalds in particular) a higher proportion of cases than controls belonged to a BME group. The proportion of the population reported as white in the 2011 UK census was 86%,87 whereas the proportion of cases and controls from a BME group ranged from 8% to 18% and from 7% to 9%, respectively, across our five studies. The generalisability of our findings to BME groups may therefore be limited.

Overall, there were few significant interactions found, but our interaction analyses should be interpreted with caution for several reasons. First, a large number of tests for interactions were performed and, although we used a significance level of 1% for these tests, one in every 100 tests will be significant by chance alone. Second, subgroup numbers were small for many comparisons, leading to insufficient power to detect anything other than large differences in associations. Third, differences in estimates of associations between complete-case and multiple imputation analyses suggest that the findings of some of our interaction analyses were not robust to missing data. Consequently, these analyses should be considered as generating rather than testing hypotheses. The significant interactions that were found need confirmation from further research.

Our findings in relation to age are, in general, in keeping with what would be expected based on child development. For example, the increased odds of falls from furniture only in 0- to 12-month-olds who were left on, had nappies changed on or who were put in car/bouncing seats on raised surfaces is to be expected given that these are activities likely to be undertaken by parents whose children are not independently mobile. We found only a small number of exposures with significant interactions with sex, with the exposure more strongly associated with an injury in boys than in girls. The majority of these were in the poisonings case–control study. Boys have higher mortality rates for poisoning than girls88 and have been found to have higher hospital admission rates for poisonings than girls,55,89 although some studies including poisonings not requiring hospital admissions have failed to find significant differences by child sex. 90,91 As our cases mainly included minor injuries, this would be consistent with finding only a few exposures more strongly associated with poisonings in boys than in girls.

There were significant interactions for several exposures related to teaching safety rules with either the number of adults in the household or the number in paid work in the stair falls and scalds studies. Previous research suggests that parents start teaching safety rules between the ages of 2 and 4 years and at this point they move from mainly using strategies based on supervision and changing the home environment to teaching- and rule-based strategies to prevent injury. 92,93 Previous research also suggests that teaching safety rules can increase the risk of injury93,94 and that teaching needs to increase children’s understanding of the safety issue to reduce the extent to which they interact with hazards. 94 Our findings suggest that cases in single adult households and in households without adults in paid work are more likely to have been taught safety rules than controls. It is possible that families in which supervision may be more challenging (e.g. single adult households) or with fewer material resources (e.g. those without adults in paid work) rely more on teaching safety rules than on other injury prevention strategies, but this may not be an effective strategy in these circumstances. Further work is required to explore these hypotheses.

The many exposures in our studies resulted in multiple significance testing; hence, some associations may have been significant by chance alone. Our estimates of associations for some exposures were imprecise because of the low prevalence of some exposures such as use of playpens or stationary activity centres, use of safety gates to prevent access to gardens, transferring household products or medicines to other containers or baths being run by older children. Some exposures were not measured in our studies because they were known to be rare, and our studies were underpowered to detect anything other than implausibly large associations. For example, bunk bed falls account for only 10% of falls from beds and have an annual incidence rate of 0.3 per 1000 children-years. 45,95–98

Comparisons with existing literature

Comparing our findings with those of previously published studies has been limited by differences in the exposures measured, similar exposures measured in different ways or inadequately detailed descriptions of exposure measures. We have not compared our findings to studies in which cases represent a wide range of injury mechanisms99 because of the difficulty in interpreting findings that are not specific to single injury mechanisms. We found only one Australian case–control study of infants with head or face trauma100 matched on age to controls with which to compare the findings from our falls studies. The findings of the Australian study were consistent with our findings for changing nappies on high surfaces (OR 1.77, 95% CI 1.07 to 2.92) and use of high chairs without harnesses (OR 1.47, 95% CI 0.73 to 2.98). We found slightly raised odds of a fall from furniture for children who had not used a baby walker (OR 1.22, 95% CI 0.90 to 1.65) but slightly reduced odds of a fall on one level (0.83, 95% CI 0.58 to 1.10) and for a fall on stairs or steps (AOR 0.83, 95% CI 0.62 to 1.09), which was consistent with the results from the Australian study (OR for ever using a baby walker 0.83, 95% CI 0.50 to 1.38). However, this was inconsistent with the increased odds of a head injury in those using a baby walker most days (OR 2.47, 95% CI 0.97 to 6.48) found by the same study.

There are several case–control studies that we can compare the findings from our poisonings study with. A study from Greece including children predominantly aged 2–4 years attending hospital emergency clinics following a poisoning and non-injured age-, sex- and hospital-matched controls attending other outpatient clinics found no significant association between mother’s use of safely packaged products, mainly for detergents, and poisoning attendance (OR not presented). 101 An Australian study of 1- to 3-year-olds attending an ED following a poisoning and three different types of controls (community, ED attenders with another type of injury and ED non-injured attenders) found that a 1% increase in the percentage of medicinal substances stored in accessible locations in bathrooms increased the odds of poisoning by 3% (OR 1.03, 95% CI 1.002 to 1.080). 102

A case–control study from Thailand of children aged < 5 years attending hospitals following a poisoning matched with controls on age, sex and area of residence found no association between toxic substances in the home, storage practices, frequency of use, packaging or disposal practices and poisoning (ORs not presented). 103 A case–control study from Brazil of children aged < 5 years treated in hospital, matched with children seeking emergency care for other reasons on age, sex, hospital and presence in the home of the same toxic substances found in the case home, found an increased odds of poisoning in families storing toxic substances in boxes/cabinets (OR 3.80, 95% CI 1.15 to 12.49) and an increased odds of poisoning in families storing toxic substances < 150 cm from the floor (OR 16.59, 95% CI 2.86 to 96.20). 104

Comparing the findings from these studies with our control findings shows some consistency in terms of our higher odds of a poisoning in families not storing medicines at adult eye level or above and in families not storing poisons safely (at adult eye level or above or locked). The previous studies have not measured associations between putting medicines or household products away immediately and poisoning, and so we cannot compare our findings in this respect.

There are several case–control studies that we can compare our scalds study with. A Greek study of children predominantly aged 0–4 years attending an ED following a burn injury, of which 61% were scalds, matched on age and sex with non-injured ED attenders, found that a 1-unit increase in a burn avoidance index was associated with a 40% reduction in the odds of a burn (OR 0.6, 95% CI 0.5 to 0.8). 105 The burn avoidance index was a composite measure consisting of direction of handles of cooking utensils on the cooker while cooking, use of front/rear hotplates during cooking, keeping hot objects, foods and liquids in places inaccessible to children and avoidance of tablecloths on kitchen tables.

A study from Iraq of children aged 0–5 years admitted to a burns centre following a burn occurring at home, of which 79% were scalds, matched on age and sex to children admitted to hospital for other reasons, found that a 1-unit increase in a burns hazard score increased the odds of a burn by 32% (OR 1.32, 95% CI 1.02 to 1.71). 106 The burns hazard score included use of kerosene cookers, kerosene heaters, samovars for tea, home generators and non-electric heaters for bathwater, not knowing the boiler temperature, storing petrol at home, having no fire extinguisher and having no smoke alarm. A Dutch study of children aged 0–4 years attending an ED with burn injuries, 62% of which were scalds, matched on age with controls, found that storage of hot drinks in their original containers instead of in vacuum flasks increased the odds of a burn (OR 2.0, 90% CI 1.2 to 3.1). 107 A study in Bangladesh of children aged 0–12 years admitted to a burns unit and controls matched on age, sex and area of residence found that significantly more case households than control households had cooking equipment within reach of children (p < 0.001; OR not reported). 108

All of these case–control studies that we can compare our scalds study findings to studied children with burns and, although most of the burns were caused by scalds in these studies, some of the differences between these studies and our findings may reflect differing case definitions. In addition, there were few common exposures between these studies and our study, which may in part reflect differences between heating and cooking practices between countries. Our findings that families who had hot drinks in reach of children, drank hot drinks while holding children or passed hot drinks over children’s heads had an increased odds of a scald are in keeping with the findings from the Greek case–control study. 105 However, as that study used a composite measure of exposure, it is difficult to know the contribution made by keeping hot foods and liquids in inaccessible places to the odds of a scald. Similarly, we did not find significant associations between cooking practices such as use of the front rings of the cooker and turning pan handles towards the back of the cooker and, although these were included in the composite exposure measure in the Greek study, the contribution of these items to the odds of a scald in that study is unknown. 105

How these findings inform other research within the Keeping Children Safe programme

The findings from study A have been used to inform the decision analyses (study K) undertaken in work stream 5 assessing the cost-effectiveness of interventions to prevent falls and poisoning. They have also been used to inform recommendations on scalds, falls and poison prevention practices in the IPB for the prevention of fire-related injuries, scalds, falls and poisoning (study M).

Research question

What are the NHS, child and family costs of falls, poisonings and scalds? Is the PedsQL an acceptable and psychometrically sound measure of HRQL in children aged ≥ 2 years in an emergency medicine setting?

Methods

Study C consisted of two substudies. In the HRQL substudy, the toddler version of the PedsQL was used to obtain proxy reports of children’s pre-injury HRQL, with questionnaires completed immediately post injury and 2 weeks and 1, 3 and 12 months post injury. Instrument acceptability, internal consistency reliability, construct validity and responsiveness to change were measured. In the costs of injury substudy, resource use and expenditure questions were included in the HRQL questionnaire. Resource use data were combined with unit costs to calculate health-care and non-health-care costs.

Results

Conclusions

The costs of injury

In the UK, there is very limited evidence on the costs of unintentional childhood injuries. However, such information is important for prioritising spending on prevention, treatment and rehabilitation services and for economic evaluations of interventions. 114–116 Several studies have attempted to quantify the economic costs associated with unintentional injuries. 30,117–122 These have been undertaken from a variety of perspectives including medical care costs,117,119,120 medical and social care costs30 or medical care, social care and societal costs. 118,121,122 However, the estimates are not always specific to children30,118,121,122 or, when they do focus on children, studies do not always present data on the under-fives. 11 Some costs are estimated based on other types of injuries, for example transposed from data on road traffic crashes. 123

Although there are some data from other countries, estimates of the economic burden of injury cannot easily be compared between countries and across time because of differences in health-care systems, the absence of standardised methodologies, the different approaches used and a lack of epidemiological and cost data. 124 It should be noted that many previous cost and HRQL studies have used populations that were likely to have sustained more serious injuries.

The costs of injury can be categorised as direct costs resulting from the injury (e.g. costs to the health-care system such as ambulance transport, ED visits, admissions, primary care attendances, rehabilitation and drug costs), indirect costs, which represent the value of lost output because of reduced productivity caused by injury and any resultant disability and losses because of premature death (e.g. costs to the child, family or society such as loss of income from carers taking time off work or lost productivity in later life by the injured or disabled child) and intangible costs (e.g. costs of pain, grief, suffering, etc.). Some studies and sources provide estimates of direct costs and some of direct and indirect costs combined, as described below, but intangible costs, which are difficult to measure in monetary terms, have not been quantified to date.

In England, unintentional injuries occurring in or around the home are a leading cause of preventable death and disability for children aged < 5 years. 1 Falls, poisonings (including suspected poisonings) and thermal injuries are the most common causes of ED attendances3 and hospital admissions. 2 Although the majority of those injuries are not severe, the disproportionately large numbers of minor injuries are likely to account for the greater costs125 compared with the costs of relatively rare serious injuries (which individually would incur substantially higher lifetime costs). 1

Each year in England, > 280,000 children aged < 5 years visit an ED as a result of falls, thermal injuries or poisoning incidents. 3 These visits cost the NHS nearly £32M, based on the average cost of an ED attendance of £114. 31 These figures do not include children treated by GPs or treated at home. 126

In 2012/13 in England, > 18,300 falls, 5100 poisonings and 1420 scalds among under-fives resulted in emergency admissions. 2 About 90% of admissions were for < 2 days but almost 16% of scalds, 4% of falls and 2% of poisonings were more serious, requiring admission for > 3 days [data available from www.chimat.org.uk/earlyyears/injuries (accessed 4 October 2016)]. In total, the admissions cost the NHS £19.1M (at £586 per short-stay case and £2461 per long-stay case). 30 The most severe childhood injuries, such as severe scalds and traumatic brain injuries (TBIs) from falls, disproportionally contribute to costs to the NHS and other care agencies because of the longer length of hospital stay, cost of treatments in intensive care units, repeated operations and long-term rehabilitation.

Falls constitute almost half of all injury-related admissions to children aged < 5 years, with a rate of between 500 and 600 admissions per 100,000 children annually between 2008/9 and 2012/13 in England. 1 A population-based study of TBIs in north Staffordshire in the 1990s reported that, among under-fives, 62% of TBI cases (of all severities) resulted from falls, rising to > 70% if children who were dropped were included. 127 A study of children admitted with a TBI to intensive care units throughout England and Wales reported that the admission rate among under-fives was 5.3 per 100,000 children annually, with falls constituting 38% of the 136 cases in the sample. 128 These injuries can impose short- or long-term problems including post-traumatic stress,129 disability and cognitive and social impairment, impact negatively on learning ability and reduce chances of future employment and productivity. They also place significant financial130 and psychological distress120,131 on children and families, and are a major economic burden to society. 132

Estimates of short- and long-term costs of injuries, predominantly based on UK data, have been highlighted in the Chief Medical Officer’s Annual Report 201211 (Table 31) and a recent report and data analysis published by Public Health England. 1 The CMO’s report estimates the costs of severe injuries for the under 15s,11 as data are more readily available for injuries in this age group, whereas the Public Health England report breaks down the data into age categories, separating the < 5 years age group, and focuses on the most common childhood injuries, including falls, poisonings and scalds. 1 Both reports highlight the high financial costs, with the short-term health-care cost per case, that is, costs related to the hospital and other health service costs immediately after the injury, ranging from £2494 for the average cost of an injury to £14,000 for a serious road traffic injury. 118 The CMO’s report notes that the lifetime cost of a childhood TBI can be up to £4.95M per case at 2012 prices. 137,138

Calculating long-term costs can be complex, as this needs to take account of the long-term consequences of sustaining a severe injury such as educational costs (e.g. special needs for a disabled child), lost productivity costs and social care costs, which are not always well documented. 1 The potential total lifetime health-care, social care and social security costs of TBI in childhood, based on the number of cases in 2003, was estimated to be between £640M and £2.24B. 11

Using the methodology developed to cost road traffic accidents, the cost of a serious home accident (one requiring admission to hospital and including medical and support costs for the acute event, lost output over the period of recovery and the value of the avoidance of injury) to a child aged < 5 years has been estimated to be £33,200 in June 2009 prices using data for Great Britain. 123 (In this study, ‘serious’ was defined in the same way as the term is used in the reporting of road casualties; namely, the injury required admission to hospital at least overnight and involved concussion, crushing, laceration of > 5 cm, suspected or actual fracture, multiple injuries or other internal injuries and the outcome of which was inpatient treatment or admission or transfer to a specialist, long-stay or other hospital.)

Several UK studies have estimated the costs of childhood scalds. An average cost of acute inpatient treatment for a minor, uncomplicated paediatric scald [one involving < 10% of the total body surface area (TBSA)] has been estimated to be £1850 in 2002/3 prices,139 whereas the average cost of acute inpatient treatment of a ‘major scald’ (30–40% TBSA) in 2007–9 in a paediatric burns unit was as high as £55,000. 119 For a bathwater scald, NHS treatment costs were £25,226 and the wider societal costs were £71,902 at 2010 prices. 140

Health-related quality of life following childhood injury

The resource and productivity costs do not fully capture the burden of childhood injuries125 as they do not take account of the quality of life of, or psychological impact on, the child and family. The most commonly used generic measure of HRQL is the European Quality of Life-5 Dimensions (EQ-5D). 141 The EQ-5D measures health using five domains to produce 243 health states to which societal preference weights are assigned to generate a single ‘utility index’ value, captured on a scale ranging from 0 [for death (or negative values for states worse than death)] to 1 (perfect health) and which depend on the severity of the health problem. 125,142 The utility index is multiplied by the time lived within a health state to calculate quality-adjusted life-years (QALYs). Thus, 1 year lived in perfect health equates to 1 QALY and a year of life lived in less than perfect health equates to < 1 QALY. The EQ-5D has previously been used to measure HRQL following injury,125,133 but at the time of initiating our study it had not been used in injured children aged < 5 years. 143 The Child Health Utility 9D is a child-specific measure of HRQL but at the time of our study it had been validated only for use in children age 7–11 years (Katherine Stevens, University of Sheffield, April 2010, personal communication).

There is a dearth of research data in the UK on the estimation of QALYs for childhood injuries. The Long Term Health and Healthcare Outcomes of Accidental Injury (HALO) study followed a cohort of serious accident casualties aged ≥ 16 years (assembled from six previous cohort studies conducted by the same research group). Health state utilities were estimated using the EQ-5D. This study reported that the average QALY loss was between 0.1 and 0.2 QALYs per year, resulting in an average loss of 1.7 QALYs (primarily because of loss of quality rather than length of life) over the following 10 years for those who survived to 6 months after injury compared with a general population, after adjusting for mortality in that general population. The study did not measure QALY loss by injury type or in children aged < 5 years. In the constituent cohorts there were 65 cases of injury victims aged < 16 years at the time of the accident but only those aged ≥ 16 years were included in the HALO follow-up cohort (HALO study final report 2009, J Nicholl, University of Sheffield, April 2010, personal communication).

In the absence of UK data measuring utility decrements associated with injury, data from other countries may be useful in estimating QALY losses. Phillips et al. 140 estimate that a bathwater scald in a young child results in a loss of 9.1 QALYs, based on a utility decrement of 0.13 ascertained from a Spanish study of burn injuries in children and adults,144 in which utilities were ascertained using the EQ-5D, multiplied by 70 additional expected life-years.

Two studies in the USA quantified QALY losses for other types of injuries (poisonings and falls). 125,145 The first of these studies did not use a validated measure of health state utilities. 125 Rather, diagnosis- and age-specific estimates of QALY losses combined physician ratings of the longitudinal impact of injuries on pain and functioning146,147 with diagnosis-specific data on the likelihood that the injury would permanently impact on the ability to work or earnings potential. 148 The physician rating scales were not specific to children, but raters were asked to rate the likelihood of impairment and duration thereof separately for children and adults. Survey data, weighting the relative importance placed by respondents on different dimensions of impact, were used to translate the estimated impairment impacts into QALYs; most of these weights were specific to children and adolescents. The utility decrements for a fall ranged from 0.1 to 0.13 and for poisoning ranged from 0.03 to 0.046. 125 The second study145 was of children aged 5–17 years following a TBI resulting from a fall and reported an average utility index, based on the Quality of Well-being Index,149,150 of 0.687 at 3 months and 0.675 at 6 months. HRQL varied widely in this study, with the utility index ranging from 0.093 to 1.0 at the 3- and 6-month interview points. 145 QALY losses have also been described by injury severity (in those aged < 20 years) in a US study for all types of childhood injuries (including poisoning and medically treated child neglect) and the values per injured case were 28.2 for fatal injury, 1.6 for an admitted case and 0.04 for a non-admitted case. 151 In this study, QALYs were computed on the basis of lives lost to fatal injuries and years of life spent in a disabled state, weighted by physician ratings of the functional loss arising from the severity of the disability; QALY losses in future years were discounted to present values at a 3% annual rate. Physician ratings were based on those routinely used by the US National Highway Traffic Safety Administration;146 the author acknowledges that these are not fully validated ratings and that they were > 20 years old at the time of writing (2006).

Methodological issues in the measurement of HRQL in children aged < 5 years are attributed to a shortage of appropriately validated instruments that are sensitive to rapid developmental stages,152 lack of health state utility classification instruments for under 5s and use of proxies in the assessment of a child’s health state. 153,154 However, proxy reporting is justified by the lack of cognitive and language comprehension skills necessary for self-completion in children aged < 5 years. 155 Parental perceptions of a child’s HRQL are also important as the principal determinant of utilisation of health-care services. 64

Studies evaluating parent–child agreement for HRQL measures found some disagreements across the domains measured, with parents of sick children tending to underestimate child HRQL and parents of healthy children tending to overestimate child HRQL. 155

The PedsQL109 has been found to be a reliable instrument for the measurement of HRQL in children, and is widely applicable in research, clinical practice and community populations. 64,109 The advantages of the PedsQL include its brevity, age-appropriate versions and parallel forms for child and parent reporting. The UK-English version has been developed and validated in children with chronic health conditions and in healthy children,156,157 and has been recommended for the assessment of HRQL in the UK.

The PedsQL has been administered in trauma injuries to under-fives158 and older children,111,158,159 including children treated for limb fractures, where it has demonstrated good responsiveness in detecting statistically significant changes in the condition of patients over time. 111,159,160 The instrument has also been used extensively for paediatric TBIs112,131,158,161,162 and spinal cord injuries. 163,164 The studies have shown a substantial long-term reduction in children’s HRQL after moderate to severe injury, particularly with regard to participation in activities, the ability to communicate and the ability to care for themselves. In addition, severe TBIs may add a considerable burden on carers and families, as reported in one study. 131

More recently, the PedsQL has been evaluated for measuring short-term outcomes for paediatric minor injuries in the ED setting, where it was found to be responsive to changes in health status over 1–2 weeks post injury. 165,166 One of the limitations of the PedsQL, however, is that it does not allow for estimation of health utilities, necessary for the estimation of QALYs. One recent study has demonstrated the feasibility of mapping the PedsQL core scales into EQ-5D utilities; however, to date this has been carried out only for older children (aged 11–15 years). 167

Ethics approval

Ethics approval was obtained from Nottingham Research Ethics Committee 1 (reference number 09/H0407/14).

Methods

Results

Discussion

Methods

The purpose of this multicentre longitudinal costs of injury study was to itemise, value and sum the costs of unintentional childhood injuries. 113 The study focused on the costs resulting from the injury borne by (1) the NHS and (2) the child and his or her family. The study did not attempt to quantify, in monetary terms, the impact on quality of life.

Results

This section presents data on the costs to the NHS, such as costs relating to ED attendance, investigations and treatments, and costs relating to hospital admission. It also includes data on other health-care resource use, for example GP visits and attendance at outpatient departments, and data on non-health-care costs incurred by the family, for example costs of over-the-counter medication, travel and child care. Results describing the characteristics of study participants who were not fully recovered at 2 weeks and who were subsequently lost to follow-up are presented elsewhere. 203

The NHS and other costs are sensitive to the proportions of injured children who are admitted to hospital and lengths of stay in hospital for different types of injuries. In this study, because the recruitment regime invited the parents of all children who were admitted to hospital to participate, the proportion admitted is substantially higher than for home accidents as a whole. Over one-third of injured children in this sample were admitted to hospital (see Table 45), although most of these were admitted for observation, not for an overnight stay. Only 4.3% of our sample were admitted overnight, which is comparable with the percentage of children in this age group attending an ED who are admitted overnight following an injury (5%). 3

Table 44 shows the numbers of questionnaires administered by injury mechanism and administration date and the numbers actually returned (see also Figure 8). It includes only those participants with complete data over the 12-month follow-up period (i.e. all questionnaires returned until complete recovery). Of the 383 2-week questionnaires returned, 32 were mini-questionnaires (see Appendix 2, Mini questionnaire) that did not contain data on resource use and these are excluded from Table 44. In addition, seven cases were lost to follow-up (1 month, n = 5; 3 months, n = 2) and their recovery status was unknown; these have also been excluded from Table 44.

To validate the accuracy of parents’ responses to questions about their children’s use of health service resources, responses from 42 parents were compared with the information contained in the medical records of their children. The results, including the kappa values illustrating interobserver agreement, are shown in Table 45. Landis and Koch79 provide a commonly used framework for interpreting kappa values:

• 0.81–1.00 – almost perfect agreement

• 0.61–0.80 – substantial agreement

• 0.41–0.60 – moderate agreement

• 0.21–0.40 – fair agreement

• 0.00–0.20 – slight agreement

• < 0.00 – poor agreement.

Care is needed in interpreting the results. Kappa values are strongly influenced by the prevalence of the outcome and there are extremes of prevalences in many of the variables, as noted in Table 45. For example, a urine test in the ED had a low prevalence of three out of 39 (8%), and all three had been misreported in the parent questionnaire, giving a kappa of 0.00, although the probability of observed agreement is 0.92. As noted, for example by Feinstein and Cicchetti,204 kappa is difficult to interpret in these circumstances [i.e. a low kappa value despite high agreement (for the prevalent category)]. There is poor agreement for observation in the ED, and advice in the ED resulting in probabilities of observed agreement of 0.63 and 0.74, respectively, resulting in kappa values of 0.26 and 0.03, respectively. This may be because the ‘medical’ interpretation of these categories differed from the parents’ interpretation.

The following procedures and visits have been omitted from Table 45 because, in the validation sample, no parents reported and/or no children had a particular procedure/visit recorded in their medical records. The omitted variables are:

• scan in the ED

• splint in the ED

• manipulation of dislocated joint in the ED

• operation to fix fracture in the ED

• physiotherapy in the ED

• stomach wash in the ED

• tetanus injection in the ED

• blood transfusion in the ED

• chest drain in the ED

• resuscitation in the ED

• hospital nurse visit(s)

• physiotherapist visits(s).

Note that because of the very small number of inpatient stays (i.e. four reported by parents and six reported in medical records, with agreement of only two) it was not possible to assess the agreement for length of stay in hospital.

Table 45 illustrates that > 95% of children were reported to have recovered from their injuries within 2 weeks of their accident and almost 99% within 1 month. However, there was variation in the proportions recovered within 2 weeks by injury mechanism, ranging from 100% for falls on one level and poisonings to 95.3% for stair falls, 91.7% for falls from furniture and 82.7% for scalds.

Parents of 435 children who reported seeking medical attention at an ED, a MIU or a walk-in centre were invited to participate, of whom 351 (81%) agreed and from whom NHS resource use information was collected via the return of the 2-week follow-up questionnaire (Table 46). Of these, 129 children (39% of those for whom admission status was known) were reported by parents to have been admitted for observation or treatment.

Based on parental questionnaires, and therefore with limited reliability, Table 47 shows that two-thirds of cases required only the lowest levels of investigation and treatment, with a further 16% of cases requiring category 2 investigations (e.g. radiography) and either category 1 or category 2 treatment. Definitions of investigations and treatment categories are provided in Table 47.

As described earlier, 344 out of 351 (98%) parents who agreed to participate provided data on recovery from injury and were included in the analysis. Seven participants who completed the 2-week questionnaire and were known not to have fully recovered at 2 weeks were subsequently lost to follow-up. These participants were similar in terms of age, sex, injury mechanism, admission status and NHS costs to those not lost to follow-up (Table 48).

Complete data were available for 288 (84%), 314 (91%) and 268 (78%) participants for NHS costs, non-NHS costs and combined NHS and non-NHS costs, respectively. In total, 95% of children were reported by parents to be fully recovered within 2 weeks of injury and 99% (n = 340) were reported to be fully recovered within 1 month of injury. Table 49 reports the characteristics of the study participants. Falls injuries were reported most frequently (75%), with 18% of injuries being poisonings and 7% being scalds. The mean age of participants was 23 months and 49% were male. Participants were relatively disadvantaged, with 43% of households receiving state benefits, 37% living in non-owner-occupied accommodation and 15% of households not having any adults in paid work. Few children (8%) had a long-term health condition prior to the injury.

Health-care resource use and costs are presented in Tables 50–54 by injury mechanism, and non-health-care resource use and costs are presented in Tables 55–57 by injury mechanism. The total health-care and non-health-care costs per child are presented in Table 58. (The sources of the costs used are shown in Appendix 2, Tables 145 and 146. )

The results in Tables 50–57 show that the burden of injury, especially on families (i.e. non-health-care costs), can be considerable, even for injuries that were treated in the ED and did not require admission. Table 57 shows that for non-admitted children, non-health-care costs can be as high as £600, although the median values across injury mechanisms were all < £10.

For children admitted for treatment (as opposed to observation), costs to families (i.e. non-health-care costs) are much higher, with scalds being the most ‘expensive’ injuries – the median cost is almost £400 and the maximum is £680 (see Table 57). It should be noted that these costs are based on responses from only three parents.

By far the largest components of the non-health-care costs were informal child care and time off work, ranging up to £670 for child care and £570 for time off work (see Table 56). However, the median costs of these components were zero in both cases, except for informal care for scalds (£22.84).

The total non-health-care costs were highest for scalds (mean £177), with a maximum of almost £700 (see Table 56). Falls from furniture were the most expensive falls (mean £71, maximum £605).

Falls can also be high-cost injuries (see Table 53) for the health sector, with total health-care costs per child ranging up to £2989 for falls from furniture. Note that in Table 52 one child incurred an inpatient stay of 15 days costing £2461 following a fall from furniture; however, because of missing responses on the self-completion questionnaire, it was not possible to obtain a total health-care cost for this child (i.e. they do not contribute a cost to Table 53). Similarly, a child who incurred a high inpatient cost of £2720 following a scald (see Table 51) was subsequently excluded from the total health-care cost calculations (see Table 53). Repeated outpatient visits and the costs associated with readmissions contribute to high health-sector costs for scalds (see Table 52).

Among children not admitted after their initial visit to the ED, health-care costs are typically between £100 and £200 (see Table 53), with scalds being slightly more expensive than other injuries.

NHS and non-NHS costs were not found to be correlated with deprivation (Figure 9), although there was some evidence that participants on benefits on average had lower non-NHS costs than those not on benefits (Figure 10). NHS and non-NHS costs by injury mechanism were similar across study centres, except for Newcastle, which was difficult to compare because of the low number of participants recruited (n = 19) (Figure 11).

FIGURE 9.

Scatterplots of costs against IMD score: (a) health-care costs; and (b) non-health-care costs. Reproduced with permission from Cooper NJ, Kendrick D, Timblin C, Hayes M, Majsak-Newman G, Meteyard K, Hawkins A, Kay B. The short-term cost of falls, poisonings and scalds occurring at home in children under 5 years old in England: multicentre longitudinal study. Injury Prevention 2016; [published online first 29 January 2016] http://dx.doi.org/10.1136/injuryprev-2015-041808. 203 Copyright © 2015 by the BMJ Publishing Group Ltd. All rights reserved.

FIGURE 10.

Box plots of health-care and non-health-care costs by benefit status. Reproduced with permission from Cooper NJ, Kendrick D, Timblin C, Hayes M, Majsak-Newman G, Meteyard K, Hawkins A, Kay B. The short-term cost of falls, poisonings and scalds occurring at home in children under 5 years old in England: multicentre longitudinal study. Injury Prevention 2016; [published online first 29 January 2016] http://dx.doi.org/10.1136/injuryprev-2015-041808. 203 Copyright © 2015 by the BMJ Publishing Group Ltd. All rights reserved.

FIGURE 11.

Box plots of health-care and non-health-care costs by study centre. Reproduced with permission from Cooper NJ, Kendrick D, Timblin C, Hayes M, Majsak-Newman G, Meteyard K, Hawkins A, Kay B. The short-term cost of falls, poisonings and scalds occurring at home in children under 5 years old in England: multicentre longitudinal study. Injury Prevention 2016; [published online first 29 January 2016] http://dx.doi.org/10.1136/injuryprev-2015-041808. 203 Copyright © 2015 by the BMJ Publishing Group Ltd. All rights reserved.

The multiple imputation model used the cost component-level data together with socioeconomic and injury data to estimate the total NHS and non-NHS costs for all participants. Table 59 shows the number of households with complete and missing cost data as well as socioeconomic and injury characteristics. The imputed results (Table 60) are comparable to the complete-case analysis with the exception of the mean cost of falls on one level (£2022, SE £1177) and falls from furniture (£2448, SE £651) for those children admitted overnight. This is likely because of the small number of children in all admitted overnight injury categories, resulting in substantial uncertainty in the mean cost estimates, portrayed by the large SEs.