Association between sunlight exposure and risk of prostate cancer: a systematic review and meta-analysis

Background The prevalence of prostate cancer (PC) is increasing worldwide. An association between sunlight exposure and PC risk has been described by a previously published meta-analysis, although the level of statistical significance was not reached. We have, therefore, performed an updated systematic review and meta-analysis to further elucidate this potential connection. Methods To identify relevant articles, we conducted an in-depth search of 4 electronic databases (PubMed, Embase, the Web of Science and Scopus) for manuscripts published prior to March 2021. A random-effects model was used to compute a meta-estimate of the effects of sunlight exposure on risk of PC. Results Of the 5680 articles that were initially identified in our search, 12 observational epidemiological studies encompassing 29 282 cases of PC were selected for inclusion in the qualitative systematic review. Of these, two case-control studies were excluded from the meta-analysis. Comparing highest-to-lowest exposure, personal sunlight exposure was significantly associated with a decreased risk of PC [odds ratio (OR) = 0.67, 95% CI: 0.57–0.78] in a random-effects meta-analysis; however, high heterogeneity was present (I2 = 85.9%). Comparing moderate-to-lowest exposure, there was a non-significant relationship between personal sunlight exposure and the risk of PC (OR = 0.87, 95% CI: 0.68–1.10; I2 = 74.0%). Conclusions Our findings indicate that exposure to sunlight may protect against PC. The limitations of our research are occurrence of publication bias and a substantial heterogeneity due to a diversity of criteria for measuring sunlight exposure.