Factors associated with asthma in young Danish adults

Background: The prevalence of asthma appears to be increasing, but our knowledge about factors associated with asthma in young adults is limited. Factors associated with asthma were studied in 624 (66% of those invited) young Danish adults (aged 19 to 29 years). Objective: The purpose of this study was to investigate the prevalence and predictors of asthma in young Danish adults. Methods: Case history, including respiratory symptoms, smoking habits, education, and employment, was obtained by interview, and a questionnaire and was used to evaluate the presence or absence of asthma. Pulmonary function, beta(2)-reversibility, airway responsiveness to histamine, and blood eosinophil count were measured using standard techniques. Results: The lifetime prevalence of asthma in these young Danish adults was 17%, and the prevalence of current asthma was 9%. The proportion of current smokers was disturbingly high, 41%, and, further, the proportion of current smokers was significantly higher among those with asthma than among those without asthma (52% and 38%, respectively; P < 0.01). Asthma was significantly associated with current smoking, with lower than predicted forced expiratory volume in I second, with lower than predicted ratio of forced expiratory volume in 1 second/forced vital capacity, atopy, higher eosinophil count, and higher degree of airway responsiveness to histamine. The proportion of subjects with no education after junior high school was higher among those with asthma than among those without asthma (P < 0.05). Further, 16 of the 103 (16%) people with asthma had work-related worsening of their respiratory symptoms. Conclusions: The presence of current asthma was predicted by current smoking, lower level of lung function, less education, higher blood eosinophil count, and more pronounced airway responsiveness. Further, the proportion of current smokers was higher among asthmatic subjects than among nonasthmatic subjects. Greater efforts must be made to encourage young people with asthma not to smoke.