Comparison of asthma prevalence in the ISAAC and the ECRHS

International and regional prevalence comparisons are required to test and generate hypotheses regarding the causes of increasing asthma prevalence in various age groups world,vide, The International Study of Asthma and Aller gies in Childhood (ISAAC) is the first such study in children and the Europ ean Community Respiratory Health Survey (ECRHS) is the first such study in adults. Therefore, a comparison of the findings of these two surveys was co nducted, for the 17 countries in which both surveys were undertaken. There was a strong correlation between the ISAAC and ECRHS prevalence data, with 64% of the variation at the country level, and 74% of the variation a t the centre level, in the prevalence of "wheeze in the last 12 months" in the ECRHS phase I data being explained by the variation in the ISAAC phase I data. There was also generally good agreement in the international patterns obser ved in the two surveys for self-reported asthma (74% of country level and 3 6% of centre level variation explained), self-reported asthma before age 14 yrs (64 and 26%), hay fever (61 and 73%) and eczema (41 and 50%), Thus although there were differences in the absolute levels of prevalence o bserved in the two surveys, there is good overall agreement between the Int ernational Study of Asthma and Allergies in Childhood and European Communit y Respiratory Health Survey study findings with regard to international pre valence patterns. These findings, therefore, add support to the validity of the two studies, which provide a new picture of global patterns of asthma prevalence from child- to adulthood, and identify some of the key phenomena which future research must address.