Children at risk of medicinal and non-medicinal poisoning: a population-based case-control study in general practice

Summary

This study found very similar risk factors for medicinal and non-medicinal poisoning. Increasing deprivation, teenage pregnancy, and being a younger child in a larger family were associated with significantly increased odds for both types of poisoning, but maternal alcohol misuse, maternal depression, and single-adult households were significant risk factors only for medicinal poisoning in multivariable models. The odds of poisoning by age showed an ‘n’-shaped relationship for both types of poisoning, but the pattern was much steeper for poisoning by medicines; compared to children aged <1 year, children aged 2–3 years were nearly 10 times more likely to have medicinal poisoning and were five times more likely to have a non-medicinal poisoning.

Strengths and limitations

Practices that contribute to THIN are broadly representative of UK general practices with regard to geographical distribution, the age and sex of patients, practice size, and data quality,20 making these findings generalisable to the UK population. Furthermore, data are entered into the database prospectively in a clinical setting, minimising recall, response, or social desirability biases associated with questionnaire-based studies. The proportion of cases with medicinal and non-medicinal poisonings in this study was similar to previous studies, which have found 65–70% of all poisonings result from medicines.9,11,16

The study did not look at the risk factors for repeat poisoning injuries or multiple poisonings occurring within the same household, and risk factor profiles in these situations may differ from those described here. Furthermore, it cannot be ruled out that some poisoning events were not Read Coded in the patient records, resulting in under-ascertainment of cases. Assuming such under-recording is not related to child or family risk factors, the effect of this would be to shift the results towards the null hypothesis, making the estimates of risk underestimates of the ‘true’ risk. Likewise, alcohol misuse is likely to be both under-reported and under-recorded, especially among those with less severe problems.21 For this reason, the definition of alcohol misuse used included only problematic drinking, frequent high levels of alcohol intake, and adverse health outcomes due to alcohol, or specific treatment for alcohol addiction. Associations may exist between less severe alcohol-related problems and childhood poisoning but these cannot be explored in large primary care database studies until the recording of alcohol intake is substantially improved. Nevertheless, the study found that maternal alcohol misuse is a risk factor for medicinal poisoning but not non-medicinal poisoning. While this may be a true difference, it must be acknowledged that, based on the sample size calculation, this may be because of the smaller number of non-medicinal cases resulting in a lack of statistical power to detect an increased risk in this group.

The measure of household composition used in this study was based on adults registered with the same GP living in the child–mother household. Given the high proportion of single-parent families in this sample compared with recent national statistics showing 24% of children live in single-parent households,22 it is plausible that some fathers were registered with a different GP, resulting in a misclassification of households as ‘single-parent’. Such misclassification, if similar for both cases and controls, would tend to underestimate the protective effect of living in households with two or more adults.

Comparison with existing literature

The study findings regarding the age at which children are at the greatest risk of each type of poisoning are consistent with previous studies,8,9,13 and are possibly explained by the development of dexterity,10 mobility, exploratory, and mouthing behaviour.7,9,23 Child development, however, cannot explain age differentials between medicinal and non-medicinal products. A potential difference may be in where these products are stored and the access that children have to them. For example, a study of safety practices by parents of young children showed that medicines are more commonly stored at or above adult eye level and cleaning products below adult eye level, with a substantial proportion stored in unlocked locations.24 Thus non-medicinal products stored at low levels are likely to be accessible to children at an earlier age, while medicines stored at higher levels will become accessible as children are able to stand well enough to reach and climb.25 In addition, children may observe parents or older siblings taking medicines, and the development of imitation behaviour around the age of 18–24 months may partly explain the higher risk of medicinal than non-medicinal poisoning in children aged over 2 years,26 and there is some evidence that increased risks of poisonings from medications may be directly related to prescribed medications for depression.27,28

The protective effect of two-adult households is consistent with findings from previous work,13 and may be explained by support with childcare, supervisory practices, and parental psychological wellbeing.8,13,29 The present findings with respect to birth order, maternal age, household composition, and deprivation are also consistent with those of other studies.8,13,16 Interestingly, it was found that child sex was not associated with either medicinal or non-medicinal poisoning, which is contrary to some previous work,7,11,30 although Beautris et al did record a similar finding,13 and, in addition, the poisoning incidence statistics reported by WHO showed only a small (0.1/100 000) difference between male and female children in poisoning rates in Europe.31

Implications for practice

This study has shown that routinely collected primary care data can be used to identify children at greatest risk of poisoning by medicinal and non-medicinal agents. Primary care clinicians have access to this information during routine consultations and should use it to target effective safety interventions. This is particularly pertinent when prescribing for children and other family members, as all prescribed medications can become poisoning agents and previous studies have shown that home safety education, including that provided by GPs, is effective in increasing safer storage of medicines and cleaning products.32,33 Despite this, other studies have shown that the number of GPs providing such advice may be small,34 and that injury prevention, while considered important in primary care, may be a low priority.35

Advice should include storing medicines and household products at or above adult eye level, preferably in locked cupboards or drawers, and putting them away after use, since most poisonings occur when substances have been left out or are in a different location following use or recent purchase.11,13 Parents should also be advised not to take medicines in front of children, because children often imitate adult behaviour. In addition, pharmacists are in a position to give advice about safe storage of medicines when they are dispensed.

This study has shown a strong association between poisoning injury and maternal alcohol misuse or depression. Prompt identification of these conditions, and early advice about safe storage and use of medicines may also reduce poisonings.