Common melanocytic nevi in 7-year-old schoolchildren residing at different latitudes in Sweden.

Background: Current epidemiologic research shows consistently that increased number of acquired common melanocytic nevi (CMN) is an important risk factor for cutaneous malignant melanoma. The purpose of this study was to investigate the number of CMN in relation to tanning habits and complexion among 7-year-old children residing at different latitudes in Sweden.

Methods: Two municipalities were chosen at latitude 65 degrees N to 68 degrees N in the north of Sweden and two at latitude 57 degrees N in the south. Children born in 1994 and registered in the municipalities were to be included (N = 1,676). A questionnaire was sent to their parents asking about the child's tanning habits. A body examination of CMN of size >or=2 mm was done by the same trained nurse in 1,380 (82.3%) of the children.

Results: CMN was significantly less prevalent among children living in the north with a prevalence of 5.6 [95% confidence interval (95% CI), 4.8-6.5] inland and 6.2 (95% CI, 5.3-7.2) coastal compared with the south with a prevalence of 9.5 (95% CI, 8.2-11.0) inland and 10.4 (95% CI, 8.9-12.0) coastal. In addition, blond hair, blue/gray/green eyes, holidays at seaside resorts abroad, more frequent sunburns, and parents fancying tanning were significant predictors of higher prevalence of CMN.

Conclusions: These findings support previous evidence that the development of CMN is related to the level of sun exposure in childhood expressed as latitude of residence, holidays at seaside resort abroad, and number of sunburns. To reduce the incidence of cutaneous malignant melanoma, a change in attitude and behavior must start with young children and their parents.