[Incidence and characteristics of adult-onset asthma]

To determine the incidence of adult-onset asthma, along with lung function and immunologic characteristics, causes, and clinical course of the disease.

After identifying incident cases of asthma among adult residents of the district of North Barcelona, Spain, we proceeded to characterize the disease using a questionnaire, lung function tests, and skin allergy tests. Patients with an occupation associated with asthma, wheezing at work, and/or sensitization to workplace allergens were considered as having occupational asthma. The risk factors for developing chronic asthma were determined by multivariate analysis.

In the 2-year study period, 218 incident cases of adult-onset asthma were identified (in a population of 68 067 adults, corresponding to an annual incidence of 160 per 100 000 per year). In total, 152 patients agreed to participate in the study (response rate, 70%); 140 reported wheezing and/or asthma in the last year (92%). The skin tests showed atopy in 57 cases (41%). Occupational asthma was diagnosed in 19 cases (14%). Domestic mammals were identified as causal agents in 8 patients (6%), drugs in 7 (5%), and environmental allergens in 44 (31%). Household cleaning was the occupation most frequently associated with the disease (26%). Of the 102 patients examined again after 2 years, 70 had chronic asthma (69%). Atopy (odds ratio [OR], 3.39; 95% confidence interval [CI], 1.15-9.99) and risk occupation when the disease was diagnosed (OR, 5.54; 95% CI, 1.05-29.11) were the factors associated with development of chronic disease.

Occupation was related to adult-onset asthma in a little over 10% of the cases and was the main determinant of the development of chronic symptoms.