Prevalence of common "acquired" nevocytic nevi and dysplastic nevi is not related to ultraviolet exposure.

The precise role of ultraviolet radiation in the induction of nevocytic nevi is unsettled. We studied mole counts in relation to the attitude toward ultraviolet exposure in 508 students 18 to 30 years of age. Moles were counted on the chest, back, and legs. Lesions measuring 2 mm or less in diameter and those measuring more than 2 mm were recorded separately. Dysplastic nevi were also recorded separately. The attitude toward sun worship was related to the average periods of sunbathing, the frequency of holidays in sunny climates, and the use of artificial ultraviolet sources. The frequency of pigmented nevi showed no correlation with sun behavior, irrespective of sex, mole size, or burning and tanning propensities. This lack of correlation between ultraviolet exposure and mole counts held true for all solar parameters: periods of sunbathing, sunny holidays, and sunlamp usage. Contrary to expectation, there was a clear, although not statistically significant, excess of dysplastic nevi in subjects with short periods of ultraviolet exposure during leisure. From these data insufficient evidence emerges to support the hypothesis of a correlation between the occurrence of common nevocytic nevi and dysplastic nevi and the degree of insolation by natural or artificial ultraviolet radiation.