PREVALENCE OF CHILDHOOD ASTHMA ACROSS CANADA

Background. A large cross-sectional study provided an opportunity to e stimate the prevalence of childhood asthma in several regions across C anada. Methods. In 1988, approximately 18 000 questionnaires were dist ributed to the families of 5-8 year old children in 30 communities fro m the following six regions across Canada: the interior of British Col umbia, southeastern Saskatchewan, southwestern Ontario, the central re gion of Ontario, southern Quebec, and the Maritimes (Nova Scotia and P rince Edward island). These communities were free of point-source air pollutants and selected to represent a range of ambient sulphate conce ntrations. In ail 14 948 questionnaires were returned representing an 83% response rate. Results. Currently present, physician-diagnosed ast hma was reported for 4.7% of children by their parents. Persistent whe ezing was reported for 13% and persistent cough for 5.9%. Asthma was m ost common in the two Maritime provinces (7.4%), and least common in B ritish Columbia (3.3%) and Quebec (3.4%). Similar regional differences were seen for persistent cough, persistent wheeze, and also hospital separation rates for asthma which were approximately 800 per 100 000 f or the Maritimes and 396 per 100 000 for British Columbia. Differences persisted despite adjustments for several host and environmental (ind oor and outdoor) characteristics. Conclusions. The east coast of Canad a may be an endemic area of asthma in Canada. It confirmed by objectiv e measures of asthma, a detailed aetiologic investigation could enhanc e understanding of this phenomenon and the major environmental determi nants of asthma morbidity in general.