To the Editors:
I would like to comment on the interesting article by van Schayck and Smit 1, which documents time trends in the prevalence of childhood asthma in a Dutch general practice registry and corresponding data from repeated cross-sectional surveys in another venue within the same country. While they and others have described an apparent levelling off and/or decline in asthma prevalence, a recent report from Denmark describes an increasing prevalence, particularly for nonatopic asthma in young females and adolescents 2. No satisfactory explanation for these time trends has been offered. I would like to propose a …