Sun exposure and the incidence of melanocytic nevi in young Australian children.

The number of melanocytic nevi (MN) is an important risk factor for cutaneous melanoma. The present study further investigated the relationship between sun exposure, the incidence of MN, and the prevalence of large acquired MN (>or=5 mm). A cohort of 479 preschool children born in Townsville, Australia was examined for MN in 1991 and a year later. Sun exposure was assessed by questionnaire. The erythemally effective dose of solar UV radiation was estimated from questionnaire data combined with local UV biometry. Almost all (97.7%) children had acquired new MN (median, 12), with a median incidence rate of 11.0 per year (interquartile range, 7.0-16.5). Total number of hours of sun exposure during follow-up (P = 0.034) and tendency to burn (P = 0.028) were independent risk factors for MN incidence. Sunburn experience during follow-up failed to reach significance when adjusted for tendency to burn. Lifetime number of sunburns (P < 0.001) and the severity of sunburns experienced during follow-up (P < 0.001) were significantly related to the presence of large acquired MN at follow-up. Reducing the total number of hours of sun exposure is particularly relevant in sun-sensitive children and may restrain the development of MN, whereas avoiding sunburn in young children might prevent large MN, subsequently reducing the risk of melanoma.