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Sun exposure is a major risk factor for skin cancer and is also an important source of vitamin D. We tested the hypothesis that elevated plasma 25-hydroxyvitamin D (25-OH-vitD) associates with increased risk of non-melanoma and melanoma skin cancer in the general population. We measured plasma 25-OH-vitD in 10,060 white individuals from the Danish general population. During 28 years of follow-up, 590 individuals developed non-melanoma skin cancer and 78 developed melanoma skin cancer. Increasing 25-OH-vitD levels, by clinical categories or by seasonally adjusted tertiles, were associated with increasing cumulative incidence of non-melanoma skin cancer (trend P=2 × 10−15 and P=3 × 10−17) and melanoma skin cancer (P=0.003 and P=0.001). Multivariable adjusted hazard ratios of non-melanoma skin cancer were 5.04 (95% confidence interval (CI): 2.78-9.16) for 25-OH-vitD 50 vs. <25 nmol l−1, and 4.02 (2.45-6.60) for top versus bottom tertile. Multivariable adjusted hazard ratios of melanoma skin cancer were 4.7 (0.96-23.3) for 25-OH-vitD 50 vs. <25 nmol l−1, and 6.3 (1.38-28.8) for top versus bottom tertile. The absolute 20-year risk was 11% for non-melanoma skin cancer and 1.5% for melanoma skin cancer, in participants with age >60 years, 25-OH-vitD winter levels 50 nmol l−1, and performing outdoor exercise. In conclusion, we show that increasing levels of 25-OH-vitD are associated with increased risk of non-melanoma and melanoma skin cancer. [ABSTRACT FROM AUTHOR]

It is possible that reduced function of DNA repair and cell-cycle control genes increases the individual susceptibility to malignant melanoma. As CHEK2 is a cell-cycle master controller, we tested the hypothesis that heterozygosity for the frameshift alteration CHEK2*1100delC is associated with increased risk of malignant melanoma. First, we performed case-control studies of 1,152 Danish and 752 German individuals with malignant melanoma compared with 9,142 Danish and 3,718 German controls. Second, we performed a meta-analysis of CHEK2*1100delC and malignant melanoma, involving 2,619 cases and 17,481 controls. Third, we examined the risk of malignant melanoma associated with CHEK2*1100delC heterozygosity in an analysis stratified for sun exposure, as well as for subtype and location on the body. The odds ratios for malignant melanoma for CHEK2*1100del heterozygotes compared with those for noncarriers were 2.01 (95% confidence interval (CI), 1.03-3.91) in Danes, 1.42 (95% CI, 0.46-4.31) in Germans, and 1.79 (95% CI, 1.02-3.17) in Danes and Germans combined. In a meta-analysis, the odds ratio of malignant melanoma for CHEK2*1100delC heterozygotes compared with that for noncarriers was 1.81 (95% CI, 1.07-3.05). Stratifications did not alter these results. CHEK2*1100delC heterozygotes have a twofold risk of malignant melanoma compared with noncarriers. [ABSTRACT FROM AUTHOR]