European journal of epidemiology
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A questionnaire of respiratory symptoms and diseases completed by 6610 adults in 3 age cohorts (35-36 y; 50-51 y and 65-66 y) in northern Sweden was followed-up by interview and lung function testing of 1243 subjects with asthmatic or bronchitic symptoms and 263 subjects assessed from the postal questionnaire as being healthy. We report the results of this follow-up study. According to the criteria used, 292 subjects (5.1% of the original study sample) were diagnosed as having asthma. ⋯ Among subjects with attacks of breathlessness and wheezing, diagnostic criteria often used for asthma in questionnaire studies, 70% were diagnosed as having asthma. Of those with chronic productive cough, 62% were diagnosed as having chronic bronchitis. We consider that trained nurses provide reliable data that may be used in epidemiological surveys of obstructive lung diseases.