[Children's relative age in class and medication for attention-deficit/hyperactivity disorder. A population-based study in a health department in Spain]

Abstract

Background and objective: Previous studies in various countries have shown that the youngest school children in the same class-grade are more likely to be treated for attention-deficit/hyperactivity disorder (ADHD) than their older classmates. The aim of this study is to determine in the Spanish setting whether younger relative age children in each grade have a higher prevalence of treatment for ADHD.

Subjects and methods: Population, observational, cross-sectional study in a health department, using prevalence data (November 2013) of treatment for ADHD in children aged 6-12 years. Data was obtained from the information systems of the Valencia Ministry of Health and multivariate models were used to estimate the prevalence ratio of treatment according to the month of birth of children in each grade.

Results: Twenty thousand two hundred and thirty-seven children were included of whom 1.73% were treated for ADHD (boys: 2.70%; girls: 0.71%) in October 2013. The prevalence of treatment increased with age, in males, and in youngest children (born in the last months of each year). In the multivariate analysis, the prevalence of treatment in the youngest children (born in the months of August to December) was 2.5 to 3 times higher than in their older classmates (born in January).

Conclusions: The younger children relative to their classmates are more likely to be treated pharmacologically with methylphenidate and/or atomoxetine.

Keywords: Age; Attention-deficit/hyperactivity disorder; Central stimulants; Children; Drug utilization; Edad; Estimulantes del sistema nervioso central; Niños; Trastorno por déficit de atención/hiperactividad; Utilización de medicamentos.