Impact of residential UV exposure in childhood versus adulthood on skin cancer risk in Caucasian, postmenopausal women in the Women's Health Initiative.

Abstract

Sun exposure is a major risk factor for skin cancer; however, the relative contribution of ultraviolet (UV) exposure during childhood versus adulthood on skin cancer risk remains unclear. Our goal was to determine the impact of residential UV, measured by AVerage daily total GLObal solar radiation (AVGLO), exposure during childhood (birth, 15years) versus adulthood (35, 50years, and present) on incident non-melanoma skin cancer (NMSC) and malignant melanoma (MM) in postmenopausal women. Women were followed with yearly surveys throughout the duration of their participation in the Women's Health Initiative Observational study, a multicenter study from 1993 to 2005. A total of 56,557 women had data on all observations and were included in the baseline characteristics. The main exposure, residential UV (as measured by AVGLO), was measured by geographic residence during childhood and adulthood. Outcome was risk of incident NMSC and MM. Over 11.9years (median follow-up), there were 9,195 (16.3%) cases of NMSC and 518 (0.92%) cases of MM. Compared with the reference group (women with low childhood and low adulthood UV), women with low childhood and high adulthood UV had a 21% increased risk of NMSC (odds ratio 1.21, 95% confidence interval 1.12, 1.31). Women with high childhood and high adulthood UV had a 19% increased risk of NMSC (odds ratio 1.19, 95% confidence interval 1.11, 1.27). Surprisingly, women with high childhood UV and low adulthood UV did not have a significant increase in NMSC risk compared with the reference group (odds ratio 1.08, 95% confidence interval 0.91, 1.28) in multivariable models. Residential UV exposure in childhood or adulthood was not associated with increased melanoma risk. This study reveals an increase in NMSC risk associated with adulthood residential UV exposure, with no effect for childhood UV exposure.