Prevalence and incidence of chronic bronchitis and farmer's lung with respect to the geographical location of the farm and to the work of farmers.

Prevalence and incidence of chronic bronchitis and farmer's lung in the Finnish farming population were studied by cross-sectional and follow-up surveys of 12,056 farmers. Occurrence of both these diseases varied greatly according to geographical location of the farm. The incidence of chronic bronchitis (2,687 new cases annually per 100,000 farmers) was twice as large in southwestern as in northern Finland. Chronic bronchitis was more common among farmers in livestock production than among those in grain production. The definition of farmer's lung adopted confined the occurrence of the disease among farmers engaged in animal tending. In livestock production, chronic bronchitis was strongly associated with swine tending, but farmer's lung with both cattle and swine tending. Use of a harvester with a sack loader turned out to be characteristic of the chronic bronchitis cases, and the number of new cases was largest among farmers who used a batch type cell drier. The farmers with grain driers that use unheated air most frequently suffered from farmer's lung. Of all (147) the characteristics of farming occupation analyzed, the methods of grain handling and drying were the most important factors for predisposing farmers to chronic bronchitis and farmer's lung.