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 2467 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.