Work is related to a substantial portion of adult-onset asthma incidence in the Finnish population

There are no population-based follow-up studies to estimate the fraction of asthma incidence that is attributable to work. In Finland, individuals wit h clinically well-established persistent asthma are registered for reimburs ement of medication from the national health insurance scheme. We combined, at an individual level, these data with the population census data of 1985 , 1990, and 1995 to estimate the attributable fraction of work in adult-ons et persistent asthma. Our follow-up study covered the entire 25- to 59-yr-o ld employed population of Finland in 1986-1998. Relative risks (RR) for occ upational categories were estimated in comparison to those employed in admi nistrative work. There were 49,575 incident cases of asthma. The attributab le fraction of occupation was 29% (95% CI 25-33%) for men and 17% (95% CI 1 5-19%) for women. The risk was increased especially in agricultural work, m anufacturing work, and service work. In addition to already established ris k occupations of occupational asthma, such as food and beverage work, the a nalysis identified a large number of occupations with significant excess of asthma incidence. The results indicate that the impact of occupational fac tors in the inception of adult-onset persistent asthma, and consequently th e potential for prevention, is much larger and more widely spread than gene rally assumed.