Emerging data suggest that reduced exposure to ultraviolet (UV) radiation is associated with increased mortality in the general population. To date, the association between UV exposure and mortality in dialysis patients has not been examined.

We examined the association between UV index, a proxy of UV exposure, and all-cause mortality among 47,286 US dialysis patients (entry period 2001-2006, with follow-up through 2009) from a large national dialysis organization using multivariable Cox regression. The UV index was ascertained by linking individual patients' residential zip codes to National Oceanic and Atmospheric Administration data, and was categorized as low (0-<3), moderate (3-<5), moderate-high (5-<6), high (6-<7), and very-high (≥7). In secondary analyses, we examined the UV index-mortality association within subgroups of age (<65 vs. ≥65 years old), sex, and race (white vs. non-white).

The study population's mean ± SD age was 60 ± 16 and included 46% women and 56% diabetics. Compared to patients residing in moderate-high UV index regions, those residing in high and very-high UV index regions had a lower mortality risk: adjusted HRs 0.84 (95% CI) 0.81-0.88 and 0.83 (95% CI) 0.75-0.91, respectively. A similar inverse association between UV index and mortality was observed across all subgroups, although there was more pronounced reduction in mortality among whites vs. non-whites.

These data suggest that dialysis patients residing in higher UV index regions have lower all-cause mortality compared to those living in moderate-high UV regions. Further studies are needed to determine the mechanisms underlying the UV index-mortality association.

Historically, vitamin D has been associated with the regulation of bone metabolism. However, increasing evidence demonstrates a strong association between vitamin D signaling and many biological processes that regulate immune responses. The discovery of the vitamin D receptor in multiple immune cell lineages, such as monocytes, dendritic cells, and activated T cells credits vitamin D with a novel role in modulating immunological functions and its subsequent role in the development or prevention of autoimmune diseases. In this review we, discuss five major areas in vitamin D biology of high immunological significance: (1) the metabolism of vitamin D; (2) the significance of vitamin D receptor polymorphisms in autoimmune diseases, such as multiple sclerosis, type 1 diabetes mellitus, and systemic lupus erythematosus; (3) vitamin D receptor transcriptional regulation of immune cell lineages, including Th1, Th17, Th2, regulatory T, and natural killer T cells; (4) the prevalence of vitamin D insufficiency/deficiency in patients with multiple sclerosis, type 1 diabetes mellitus, and systemic lupus erythematosus; and finally, (5) the therapeutic effects of vitamin D supplementation on disease severity and progression.