VANCOUVER, B.C.—Deficiency in 25-hydroxyvitamin D [25(OH)D] is independently associated with an increased risk of death from any cause among patients with chronic kidney disease (CKD), according to researchers. In addition, the likelihood of 25(OH)D deficiency increases with body mass index (BMI).

Investigators at Cleveland Clinic in Ohio found that 25(OH)D deficiency—which they defined as a level below 15 ng/mL—was associated with a 33% increased risk of death after adjusting for multiple variables. The effect was similar for Caucasians and African Americans. The study showed that 25(OH)D insufficiency (levels between 15-29 ng/ml) was not significantly associated with increased mortality.

The study, by Sankar Navaneethan, MD, and colleagues, included 12,763 stage 3 and 4 CKD patients. Of these, 1,970 (15%) were 25(OH)D deficient and 5,749 (45%) were had 25(OH)D insufficiency.

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Compared with patients with a BMI of 18.5-24.9 kg/m2, those with a BMI of 30-34.9 had an approximately 1.5 times increased risk of 25(OH)D deficiency, the researchers reported at the World Congress of Nephrology. Those with a BMI of 35-39.9 and 40 or higher had a nearly twofold and threefold increased risk, respectively.

The new findings are in line those of a recently published study (online ahead of print) in Nephrology Dialysis Transplantation, which found that low levels of 25(OH)D are associated with an increased risk of all-cause and cardiovascular mortality in CKD patients. Each 10 ng/mL increment in 25(OH)D levels was associated with a 37% and 41% decreased risk of all-cause and cardiovascular mortality.

Dr. Navaneethan cautioned, however, that “we cannot infer causality from available observational data on this topic.”

Future studies should examine the mechanism underlying the associations between vitamin D and overall mortality in CKD and whether supplementation with 25(OH)D reduces cardiovascular and all-cause mortality rates, he said.