Do Sunscreens Increase Risk of Melanoma in Populations Residing at Higher Latitudes?

Background Sunscreens may allow overexposure to ultraviolet A (UVA) in fair-skinned persons and prevent symptoms of sunburn, but their benefits for the prevention of melanoma are uncertain. Methods A PubMed search was performed that identified all known studies of the association of sunscreen use with melanoma risk during 1966-2007. A total of 18 studies were identified, of which 17 met criteria for inclusion in the analysis. Of these, 10 were conducted at latitudes >40° from the equator and 7 at ≤40°. Data were pooled for all latitudes combined and also according to these latitude strata. The association of skin pigmentation and latitude with odds ratios was estimated using linear regression. Results Overall, there was no statistically significant effect of use of sunscreens on risk of melanoma (odds ratio 1.2, 95% confidence interval [95% CI] 0.9–1.6; p for heterogeneity < 0.0001). However, there was an interaction with latitude. At >40° from the equator, the odds ratio was 1.6 (95% C.I. 1.3–1.9; p for heterogeneity = 0.006), whereas it was 0.7 at ≤40° (95% C.I. 0.4–1.0; p for heterogeneity = 0.0002). Conclusions Use of common sunscreen formulations that absorb UVB almost completely, but transmit large quantities of UVA, may contribute to risk of melanoma in populations at latitudes >40°.