Changing trends in asthma in 9-12 year olds between 1964 and 2009

Introduction Childhood asthma is a common condition and the prevalence has increased in many countries during the late 20th century. The Aberdeen schools asthma surveys reported rising lifetime prevalence of asthma between 1964 and 2004 in children aged 9-12 years, but a fall in wheeze in the last 3 years between 1999 and 2004. The present study tested the hypothesis that lifetime childhood asthma prevalence has fallen since 2004. Methods Children aged 9-12 years who attended the same schools surveyed since 1964 were invited to participate. A lifetime history of asthma or eczema and also wheeze in the past 3 years and 12 months was ascertained from a questionnaire. Trends over 1999, 2004 and 2009 were analysed with adjustment for age, gender and an index of deprivation. Results There were 2253 eligible children and 1196 (53%) questionnaires were returned. The lifetime prevalence of asthma rose from 24.3% in 1999 to 28.4% in 2004 but fell to 22.1% in 2009 (p<0.001), while wheeze in the last 3 years fell from 27.9% in 1999 to 25.2% in 2004 and fell further to 22.2% in 2009 (p<0.001). The lifetime prevalence of eczema among 9-12 year olds was 21.4% in 1999, 34.1% in 2004 and 30.7% in 2009 (p<0.001). Reductions in symptom prevalences between 2004 and 2009 were significant for girls but not boys. Conclusion The prevalence of lifetime asthma and wheeze appear to have fallen in school children, especially girls, although the low response rate means some caution is required when interpreting the results. Asthma prevalence remains high and the underlying mechanisms remain incompletely understood.