Serum 25-hydroxyvitamin D and cancer risk in older adults. Results from a large German prospective cohort study

Abstract
Background: Several observational studies assessed the relationship between serum 25-hydroxyvitamin D (25(OH)D) concentrations and the risk of cancer but results were inconclusive.

Methods: We measured 25(OH)D concentrations in a population-based cohort study of 9,949 men and women aged 50-74 in Saarland, Germany. Comprehensively adjusted Cox regression models were applied to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the association between season-standardized 25(OH)D concentrations and total and site-specific cancer incidence.
Results: Overall, during a median of 8 years of follow-up, 873 subjects developed cancer; the most common being prostate (171), breast (137), lung (136) and colorectal (136) cancer. Low season-standardized 25(OH)D (<30, 35, 40 or 36 nmol/L in winter, spring, summer and autumn, respectively) was neither significantly associated with total cancer incidence (HR, 1.10; 95% CI, (0.93-1.30)) nor with site-specific cancer incidence. However, a significantly increased overall cancer risk was observed for low 25(OH)D among men, non-obese subjects and subjects reporting low fish consumption and for high 25(OH)D in non-smokers and non-obese subjects. Accordingly, restricted cubic splines to investigate dose-response relationships curves showed an inverse association of 25(OH)D levels and total cancer risk in men but not in women.
Conclusions: 25(OH)D concentrations were significantly associated with overall cancer incidence in subgroups of this large cohort from Germany. No significant association was observed with site-specific cancers but this could be due to a limited statistical power for these endpoints.
Impact: Further research should clarify if and to what extent specific risk groups might profit from vitamin D supplementation.