Objective—To compare reported safety practices between responders and non-responders to a safety survey.
Design—Cross sectional survey at baseline compared with safety practices reported at subsequent child health surveillance checks.
Subjects—Parents of children aged 3–12 months registered with practices participating in a controlled trial of injury prevention in primary care that did, and did not, respond to the baseline survey and who subsequently attended child health surveillance checks.
Results—No difference in safety practices was found between responders and non-responders to the survey at the 6–9 month check. Responders were more likely to report owning a stair gate (odds ratio (OR) 2.75, 95% confidence interval (CI) 1.82 to 4.16) and socket covers (OR 2.16, 95% CI 1.53 to 3.04) at the 12–15 month check, and owning socket covers (OR 2.19, 95% CI 1.34 to 3.61) at the 18–24 month check. Responders were more likely to report greater than the median number of safety practices at the 18 month check.
Conclusions—Non-responders to a safety survey appear to be less likely to report owning several items of safety equipment than responders. Further work is needed to confirm these findings. Extrapolating the results of safety surveys to the population as a whole may lead to over estimation of safety equipment possession.
- safety practice
- data collection
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Safety surveys are often undertaken for planning or evaluating injury prevention programmes. The published literature suggests non-responders to surveys differ systematically from responders,1–13 but little of this relates to non-responders to safety questionnaires. If surveys are used for planning injury prevention programmes, having information on the safety practices of non-responders is important. As part of a controlled trial of injury prevention we have obtained information on some safety practices among responders and non-responders to a safety questionnaire. This has enabled an assessment of whether a response bias occurred, and if so, its direction and magnitude.
A postal questionnaire was sent in July 1995 to all parents of children aged 3–12 months registered with 36 practices in areas ranging from the deprived to the affluent in Nottingham. The questionnaire, which was tested for reliability,14 was sent before the interventions commenced. It included sections on safety equipment and safety practices, perceptions of risk of injury and of hazards, knowledge and confidence in dealing with first aid, sociodemographic characteristics, and history of previous injury.
Parents attending routine child health surveillance (CHS) checks at 6–9 and 18–24 months with the health visitor, and at 12–15 months with the practice nurse were asked to complete a carbonated checklist asking about possession of safety equipment and safety practices. The checklist was then used as the basis of the safety advice given by the health visitor or practice nurse as part of the trial intervention. All intervention group parents, regardless of their response to the postal questionnaire, were eligible to receive the study interventions including safety advice at CHS contacts, home safety checks, low cost equipment (for those receiving means tested benefits), and first aid training. Fewer parents received advice at the 6–9 month and 12–15 month checks than the 18–24 month check as some children participating in the study had already received these checks by the start of the study, and were therefore only eligible for those checks they had not yet received.
Data were analysed using SPSS for windows version 8.0 and STATA version 5. Comparisons of self reported safety practices at each CHS check were made between responders and non-responders to the postal questionnaire, using χ2 tests and by calculating the odds ratio (OR) and 95% confidence interval (CI) for each safety practice, with the standard error adjusted for clustering. A subgroup analysis has been undertaken comparing safety practices between responders and non-responders who did not receive safety equipment as part of the study. The number of interventions received and the safety practices reported were not normally distributed. In order to compare the number of interventions and safety practices between those completing and those not completing the safety questionnaire, with adjustment for clustering, responders and non-responders have been dichotomised into two groups. The groups have been defined as having more than the median number of interventions or safety practices, or less than this. In view of the multiple comparisons reported here, a significance level of 0.01 has been used.
The results relate only to the intervention group of the study. The response rate to the questionnaire was 73.2% (n = 823). Non-responders numbered 301, 24 of whom left Nottingham before the interventions commenced. The sociodemographic characteristics of responders to the questionnaire are shown in table 1. Non-responders comprised 18% of those receiving advice at each of the CHS checks (57/315 at the 6–9 months check, 82/463 at the 12–15 month check, and 95/535 at the 18–24 month check). A third or fewer non-responders received advice at any of the CHS checks (21% at the 6–9 month check, 30% at the 12–15 month check, and 34% at the 18–24 month check). Overall, responders to the questionnaire were much more likely to have received greater than the median number of interventions than non-responders (OR = 8.66, 95% CI 5.34 to 14.03; p<0.001).
There was no difference between the self reported practices among responders and non-responders to the questionnaire at the 6–9 month check. Tables 2 and 3 show the safety practices reported by responders and non-responders to the questionnaire at the 12–15 month and the 18–24 month checks respectively. Responders to the questionnaire are more likely to report owning some items of safety equipment than non-responders at both time points. Responders were more likely to have more than the median number of safety practices than non-responders at both the 12–15 month (OR 2.12, 95% CI 1.10 to 4.09; p=0.03) and the 18–24 month check (OR 1.86, 95% CI 1.16 to 2.98; p=0.01).
As the interventions included the provision of low cost safety equipment, we have repeated the analyses among those who did not receive equipment from the study. This produced similar results. No differences were found between safety practices at the 6–9 month CHS check (n = 272). At the 12–15 month check (n = 411), responders were more likely to report having a stair gate (OR 3.14, 95% CI 1.89 to 5.21; p<0.001) and socket covers (OR 2.44, 95% CI 1.76 to 3.40; p<0.001). At the 18–24 month check (n = 471) responders were more likely to report having socket covers (OR 2.27, 95% CI 1.38 to 3.74; p=0.001).
Safety equipment possession does appear to differ between responders and non-responders to a safety questionnaire. Responders are 2–3 times more likely to report possessing stair gates and socket covers locks when their child is 12–24 months of age than non-responders. In addition responders report a higher number of safe practices than non-responders.
While our results suggest differences in safety practices between responders and non-responders, there are several possible explanations for this. Firstly completing a questionnaire may raise awareness of home safety and may change behaviour by encouraging parents to obtain safety equipment. If this was the case, the greatest difference between responders and non-responders would be expected at the first CHS check after completion of the questionnaire. However, we were unable to find any differences between the groups at the 6–9 month check. Completion of the questionnaire may encourage parents to obtain safety equipment in the future; for example, when the child becomes more mobile. Alternatively parents who are more likely to obtain equipment as the child becomes more mobile may be more likely to respond to the questionnaire.
Secondly, the safety practices reported on the questionnaire and at the CHS checks were self reported; and as such may overestimate safe practice.15 Responding families may have over reported owning safety equipment to a greater degree than non-responding families. It seems unlikely that families would report owning equipment they do not possess as it was available at low cost in the study. It also seems unlikely that responders, who were more likely to request, and to have a home safety check (27.3% responders v 4.5% non-responders, χ2 = 65.9, 1 df; p<0.001), would report having items of equipment which they did not possess, when they will be visited by the health visitor for a home safety check.
The differential safety equipment reporting cannot be explained by receipt of the study interventions as the findings were similar for parents who did not obtain safety equipment as part of the study. We have not been able to find any published work that has examined safety practices among non-responders to a safety questionnaire with which to compare our results. There is a large body of work which suggests that responders to surveys differ from non-responders in terms of sociodemographic characteristics, ethnicity, and interest in the topic covered in the questionnaire.113 This suggests that non-responders tend to belong to groups that are likely to have a higher risk of unintentional injury. It would therefore not be surprising to find that non-responders differed in terms of safety practices as well. Furthermore, it is a weakness of our study that we were only able to examine safety practices in non-responders who attended CHS checks. Parents not attending CHS checks are likely to differ from those who attend. Lower rates of uptake of child immunisation have been found among the socioeconomically disadvantaged.16–18 Non-attendance at child health clinics has been found to be associated with older maternal age,19 and in several studies with socioeconomic disadvantage.20,21 Therefore, it is possible that non-attending non-responders may report fewer safety practices than those attending. If this were the case, our findings would represent a conservative estimate of the difference between responders and non-responders.
Safety surveys are often used for planning or evaluating injury prevention programmes, but little work exists examining the safety practices of non-responders to safety surveys.
Analysis of data from this study suggests a response bias does exist and that non-responders are less likely to report owning several items of safety equipment than responders.
Further work is needed to confirm these findings.
Extrapolating the results of safety surveys to the population as a whole may lead to an over-estimation of safety equipment possession.
Where possible, planners and evaluators should consider collecting data on sociodemographic characteristics, safety practices, and injury occurrence among non-responders.
We conclude that our study suggests that non-responding families are less likely to report possessing some items of safety equipment and that further work confirming this finding would be useful. If this is confirmed, extrapolating the results of safety surveys to the population as a whole may be of questionable validity and may lead to over estimation of safety equipment possession. Wherever possible, information on sociodemographic characteristics, safety practices, and the injury experiences of non-responders should be sought to help inform the generalisability of such surveys.
We would like to thank Carol Coupland for advice on analysis of clustered data.
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