Habits of sun exposure and risk of malignant melanoma: an analysis of incidence rates in Norway 1955-1977 by cohort, sex, age, and primary tumor site.

Incidence data on malignant melanoma of the skin in Norway from 1955-1977, comprising a total of 5108 new cases, were analyzed according to cohort, sex, age, and primary tumor site. A continuous increase in incidence of approximately 7% per year was observed for both sexes during the study period. For trunk and lower limb melanomas, the increase and cohort variations in incidence were much greater than for face and neck melanoma. A difference between these site groups was also observed in the shape of the cohort curves of age-specific rates. This indicated that the trend in carcinogenic exposure through life was different for the face--neck and the trunk--lower limb. For the generations born 1930-1949, the incidence of malignant melanoma per area unit of skin was greater for the trunk and lower limb than for the face--neck. It is suggested that not only the cumulated dose, but also the intensity of solar radiation may be significant in the cause of malignant melanoma.