Time trend for the prevalence of asthma among school children in a Swedish district in 1985-2005

Aim: To assess the temporal trend for asthma and asthma-like symptoms over a period of 20 years. Method: Repeated cross-sectional surveys with identical study design were carried out among all school children (7-16 years) in a well-defined area in Sweden in 1985, 1995 and 2005. Results: In 2005, the parents of 1110 out of 7825 children (14.2%) answered yes to a screening question on asthmatic symptoms. Of these, 783 out of 1110 (70.5%) replied to a postal questionnaire with detailed questions concerning symptoms and asthma management. The rate of affirmative response to the screening question was unchanged between 1995 and 2005. However, the percentage of children with wheezing or three or more asthma-like symptoms decreased, whereas the percentage of children with physician-diagnosed asthma increased steadily since 1985. The number of reported symptoms was closely associated with the number of days with physical restriction. The annual sale of inhaled steroids from local pharmacies was stable between 1995 and 2005. Conclusion: The increase in asthmatic symptoms in school children has peaked. Reduced severity of symptoms and divergent trends for wheezing and physician-diagnosed asthma suggest an increased awareness of asthma with improved management of the symptoms. However, differences in trends between allergic and nonallergic asthma could not be excluded.