Childhood sun exposure as a risk factor for melanoma: a systematic review of epidemiologic studies

Objective: To review the evidence that childhood is a period of particular susceptibility to the carcinogenic effects of solar radiation. Methods: Studies were identified through searches of computerized bibliogra phic databases and article reference lists. Eligible studies were those tha t reported risks of melanoma associated with sun exposure during two or mor e age-periods. Results: The measurement of childhood sun exposure varied across studies, p reventing formal meta-analysis for most measures. We found that the way in which sun exposure was measured led to strikingly different conclusions reg arding the association between age-specific sun exposure and risk of melano ma. Ecological studies assessing ambient sun exposure consistently reported lower risks of melanoma among people who resided in a low ultraviolet (UV) environment in childhood compared with those who resided in a high UV envi ronment. In contrast, case-control studies differed widely in their finding s, and no consistent associations with childhood sun exposure were observed . Conclusions: Ecological studies provided better-quality evidence than case- control studies for examining the effects of exposure to sunlight during sp ecific age periods. Exposure to high levels of sunlight in childhood is a s trong determinant of melanoma risk, but sun exposure in adulthood also play s a role.