Vitamin D and cancer mortality in elderly women

BACKGROUND: There is increasing evidence that vitamin D deficiency is a risk factor for cancer, however it remains uncertain whether vitamin D deficiency also predisposes to death from cancer. The aim of the study was to determine the association between serum 25-hydroxy-vitamin D (25 (OH) D) concentrations and cancer-specific mortality in a community-based cohort of older post-menopausal women. METHODS: Cox proportional regression analyses were conducted to examine the association between serum 25 (OH) D concentrations and the risk of overall and site-specific cancer mortality in a cohort of elderly women. RESULTS: Over a median follow-up time of 10 years, a total of 84 cancer deaths were observed. Women with lower serum 25 (OH) D concentrations were at an increased risk of cancer death, but not for incident cancer. The excess risk for cancer death was observed with serum 25 (OH) D concentration less than 64 nmol/L (the median value) [adjusted HR: 1.61 (95% CI: 1.02 - 2.54, p = 0.04]. For every 30 nmol/L reduction in serum 25 (OH) D concentrations, there was a 30% increase in the overall risk of cancer death [adjusted HR: 1.33; 95% CI: 1.03 – 1.72, p = 0.02]. The excess risk appeared to be site-specific and greatest in those with haematological cancers [adjusted HR: 2.13: 95% CI: 1.0 – 4.55, p = 0.05]. CONCLUSIONS: In elderly women, lower serum 25 (OH) D concentrations appear to be an independent risk factor for cancer-specific mortality, but not a risk factor for the development of cancer. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12885-015-1112-5) contains supplementary material, which is available to authorized users.