Malignant melanoma in Denmark. Occurrence and risk factors.

The age-standardized incidence rate of cutaneous malignant melanoma (CMM) in Denmark increased five- to six-fold between 1943 and 1982. The increased varied by sex and by site, being particularly pronounced for areas of the body normally covered by clothes. A steep increase in risk was revealed for successively younger birth cohorts. Lack of consistency between descriptive epidemiology and indicators for cumulative exposure to sunlight has led to the intermittent exposure hypothesis. Our population-based case-control study, including 474 incident cases of CMM and 926 controls, has further supported this hypothesis and demonstrated that sunbathing is associated with an increased risk of CMM, particularly during childhood and if it leads to sunburning. In addition, the risk of CMM is increased in persons with many pigmented naevi and/or a tendency to freckling. Our study does not support a relationship between CMM and hormonal exposure in women and no association was observed between dietary factors, alcohol intake, tobacco smoking, bathing habits or hair dye use and CMM risk.