Prevalence of asthma and related symptoms in junior high school children in Isfahan, Iran.

Asthma is the most common chronic disease in children. There are scattered epidemiological data concerning the prevalence of this disorder in developing countries. From October 1998 to May 1999 we studied 4069 randomly selected, junior high-school children in urban areas of Isfahan for asthma and related symptoms. The ages were expected to be 12-15 years. The children completed a questionnaire, and 3924 completed questionnaires were returned (response rate = 96.4%). Pupils with chronic respiratory symptoms were interviewed, physically examined at hospital and 1710 of them also underwent post exercise spirometry. The overall prevalence of asthma ever in life was 9.5%, with a male to female ratio of 2/1. The frequencies of current asthma, wheezing ever in life and exercise induced wheezy breathing were 7.3%, 19.1% and 14.2% respectively. Wheeze was heard on chest auscultation in 4.1% of the children. Pulmonary function tests revealed forced expiratory volume in 1 sec (FEV1) < 80% in 5.9%, forced mid-expiratory flow (FEF25-75) < 70%, in 9.7% and FEF75 < 70% in 20.6% of the tested children. All of the later findings strongly correlate with history of asthma. Parental smoking, similar illness in parents and/or siblings, lower levels of parental education and presence of cats, cockroaches and chicken in the household were significant risk factors. The prevalence of asthma in the students of the junior high schools of Isfahan is not far less than the average rates reported in many parts of the world, and it seems necessary to pay more attention to poorly controlled air pollution in Isfahan as an industrial city.