Prevalence of pigmented naevi in a Swedish population living close to the Arctic Circle.

The prevalence of common naevi and dysplastic naevi was investigated in a Swedish population with a low incidence of melanoma. A total of 201 subjects aged 30-50 years living in northern Sweden participated. The median number of common naevi per individual was 15, and 11% had dysplastic naevi. Higher numbers of common naevi were found in individuals with dysplastic naevi (median 68) and in those who had spent their childhood in southern Sweden (median 44). The prevalence of common naevi and dysplastic naevi was significantly lower than reported from a previously studied population in southern Sweden, with a melanoma incidence 4 times higher than in the north. The strong variability in naevus phenotype, and in melanoma incidence, between different regions of Sweden seems to be due to different levels of sun exposure rather than to differences in constitutional factors.