RESUMO
BACKGROUND: Although asthma is a common cause of morbidity in adults, relatively few objectively measured population studies of asthma prevalence in adult populations have been conducted. OBJECTIVE: To evaluate the prevalence of asthma, based on both a questionnaire and methacholine bronchial provocation test, and to determine the risk factors of asthma prevalence in an adult population. METHODS: A total of 2,467 adults, who were randomly selected from metropolitan urban, non-metropolitan urban and rural areas, responded to the modified ISAAC questionnaire, and underwent methacholine bronchial provocation tests and skin prick tests to locally common aeroallergens. RESULTS: The prevalence of current asthma based on the questionnaire and the methacholine challenge was 2.0% in adults younger than 40, 3.8% in 40- to 54-year-olds, 7.7% in 55- to 64-year-olds and 12.7% in those aged 65 or higher. For subjects of 55-64 years, active smoking was found to be significantly related with the prevalence of current asthma and bronchial hyper-responsiveness, although smoking was positively associated with percentage predictive value of forced expiratory volume of 1 s (FEV1). CONCLUSION: The prevalence of current asthma is common among the elderly, and active smoking may play an important role in the development of asthma and bronchial hyper-responsiveness among the elderly.