Ecologic studies have reported that solar ultraviolet radiation (UVR) exposure is associated with cancer; however, little evidence is available from prospective studies. We aimed to assess the association between an objective measure of ambient UVR exposure and risk of total and site-specific cancer in a large, regionally diverse cohort [450,934 white, non-Hispanic subjects (50-71 years) in the prospective National Institutes of Health (NIH)-AARP Diet and Health Study] after accounting for individual-level confounding risk factors. Estimated erythemal UVR exposure from satellite Total Ozone Mapping Spectrometer (TOMS) data from NASA was linked to the US Census Bureau 2000 census tract (centroid) of baseline residence for each subject. We used Cox proportional hazards models adjusted for multiple potential confounders to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for quartiles of UVR exposure. Restricted cubic splines examined nonlinear relationships. Over 9 years of follow-up, UVR exposure was inversely associated with total cancer risk (N = 75,917; highest versus lowest quartile; HR = 0.97, 95% CI = 0.95-0.99; p-trend < 0.001). In site-specific cancer analyses, UVR exposure was associated with increased melanoma risk (highest versus lowest quartile; HR = 1.22, 95% CI = 1.13-1.32; p-trend < 0.001) and decreased risk of non-Hodgkin's lymphoma (HR = 0.82, 95% CI = 0.74-0.92) and colon (HR = 0.88, 95% CI = 0.82-0.96), squamous cell lung (HR = 0.86, 95% CI = 0.75-0.98), pleural (HR = 0.57, 95% CI = 0.38-0.84), prostate (HR = 0.91, 95% CI = 0.88-0.95), kidney (HR = 0.83, 95% CI = 0.73-0.94) and bladder (HR = 0.88, 95% CI = 0.81-0.96) cancers (all p-trend < 0.05). We also found nonlinear associations for some cancer sites, including the thyroid and pancreas. Our results add to mounting evidence for the influential role of UVR exposure on cancer.
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