How much adult asthma can be attributed to occupational factors?

PURPOSE: Many occupational factors can cause asthma or reactivate preexisti ng disease. We carried out a critical review and synthesis of the available literature to estimate the proportion of adult asthma that is attributable to workplace factors. METHODS: We reviewed published citations from 1966 through May 1999 as well as recent abstracts of studies providing risk estimates for asthma among v arious occupations. We extracted published attributable risk estimates, der ived others from published data, and extrapolated estimates from the incide nce rates of occupational asthma. We used a semiquantitative score to rank studies based on their characteristics. RESULTS: We obtained 43 attributable risk estimates from 19 different count ries: 23 were published estimates, 8 were derived from published data, and 12 were extrapolated from incidence data. The median value for the attribut able risk of occupationally associated asthma was 9% (25th to 75th interqua rtile range: 5% to 19%). The derived estimates (median attributable risk = 25%) were significantly greater than published values (median = 9%, P = 0.0 02), whereas the extrapolated estimates were significantly lower (median = 5%, P = 0.04). The 12 highest scored studies based on their characteristics yielded a median risk estimate of 15%. CONCLUSION: Occupational factors are associated with about 1 in 10 cases of adult asthma, including new onset disease and reactivation of preexisting asthma. Am J Med. 1999;107: 580-587. (C) 1999 by Excerpta Medica, Inc.