Incidence of asthma and mortality in a cohort of young adults: a 7-year prospective study

Background: Few longitudinal data exist on the incidence of asthma in young adults and on the overall mortality risk due to asthma. A 7-year follow-up prospective study was performed to assess the incidence of asthma and mortality from all causes in a cohort of young adults. Methods: The life status of a cohort of 6031 subjects, aged 20 - 44 years, who replied to a respiratory screening questionnaire between 1991 and 1992, was ascertained in 1999. A new questionnaire investigating the history of asthma was subsequently sent to the 5236 subjects who were still alive and residents in the areas of the study. 3880 subjects (74%) replied to the second questionnaire. Results: The incidence of adult-onset asthma was 15.3/10,000/year (95% CI: 11.2 - 20.8). The presence of asthma-like symptoms (IRR: 4.17; 95% CI: 2.20 - 7.87) and allergic rhinitis ( IRR: 3.30; 95% CI: 1.71 - 6.36) at baseline were independent predictors of the onset of asthma, which was more frequent in women ( IRR: 2.32; 95% CI: 1.16 - 4.67) and increased in the younger generations. The subjects who reported asthma attacks or nocturnal asthma symptoms at baseline had an excess mortality risk from all causes (SMR = 2.05; 95% CI: 1.06 - 3.58) in the subsequent seven years. The excess mortality was mainly due to causes not related to respiratory diseases. Conclusion: Asthma occurrence is a relevant public health problem even in young adults. The likelihood of developing adult onset asthma is significantly higher in people suffering from allergic rhinitis, in women and in more recent generations. The presence of asthma attacks and nocturnal symptoms seems to be associated with a potential excess risk of all causes mortality.