Incidence of farmer's lung leading to hospitalization and its relation to meteorological observations in Finland.

The standardized annual incidence of farmer's lung (FL) leading to hospitalization during 1980 in Finland was 50 per 100 000 persons employed in farming. Using preset uniform criteria, data were collected from all pulmonary disease units in the country. There were 186 new cases of FL in 1980. The mean age was 46 years, and 64% were women. Using the national population in 1975 as standard, the rates were standardized for age and sex. There were differences both in the incidence and in the sex ratio of FL among the farming population of the six districts of Finland. These differences are closely related to prevalent proportions of cattle raising among farmers and local cultural traditions in the various districts. Seasonal variation in the incidence of FL was statistically significant (Roger's test, p less than 0.001), the peak occurring in April. This confirms an earlier observation. The incidence rates were statistically significantly correlated with the sum and the mean of daily rainfall during the haymaking period preceding the diagnosis of FL.