Simultaneous assessment of risk factors for malignant melanoma and non-melanoma skin lesions, with emphasis on sun exposure and related variables.

The purpose of this case-control study was to identify differences in risk factors between melanoma and non-melanoma skin lesions. The study group, interviewed from 1979 to 1982, consisted of 289 subjects with melanoma, 75 subjects with non-melanoma sun-related skin lesions and 527 controls. Simultaneous comparison of the three subgroups was accomplished by polychotomous logistic regression. The highest exposure category of lifetime sun exposure was associated with a nearly threefold risk of both melanoma and non-melanoma. Poor tanning was associated with an approximately twofold risk of both disease types. Similarly, northern European ethnicity was associated with an approximately twofold risk of disease. Number of moles on the body exhibited a relationship with melanoma only: having more than 25 moles, compared to their absence, was associated with a thirteenfold risk of melanoma. History of freckling was associated with a twofold risk of melanoma, but no increase in the risk of non-melanoma. Alternatively, mixed indoor-outdoor recreational exposure was associated with a 50% increased risk of non-melanoma, but a 25% decreased risk of melanoma. History of severe sunburn was associated with a twofold risk of non-melanoma only. For history of prior sun-related lesions the nearly sevenfold risk of melanoma was exceeded by the 14-fold risk of non-melanoma.