Prevalence of symptoms of severe asthma and allergies in irish school children: An ISAAC protocol study, 1995-2007

Childhood asthma is a recurring health burden and symptoms of severe asthma in children are also emerging as a health and economic issue. This study examined changing patterns in symptoms of severe asthma and allergies (ever eczema and hay fever), using the Irish International Study of Asthma and Allergies in Childhood (ISAAC) protocol. ISAAC is a cross-sectional self-administered questionnaire survey of randomly selected representative post-primary schools. Children aged 13-14 years were studied: 2,670 (in 1995), 2,273 (in 1998), 2,892 (in 2002-2003), and 2,805 (in 2007). Generalized linear modelling using Poisson distribution was employed to compute adjusted prevalence ratios (PR). A 39% significant increase in symptoms of severe asthma was estimated in 2007 relative to the baseline year 1995 (adjusted PR: 1.39 [95% CI: 1.14-1.69]) increasing from 12% in 1995 to 15.3% in 2007. Opposite trends were observed for allergies, showing a decline in 2007, with an initial rise. The potential explanations for such a complex disease pattern whose aetiological hypothesis is still evolving are speculative. Changing environmental factors may be a factor, for instance, an improvement in both outdoor and indoor air quality further reinforcing the hygiene hypothesis but obesity as a disease modifier must also be considered.