Vitamin D status and mortality risk among patients on dialysis: A systematic review and meta-analysis of observational studies

Abstract

Background. Vitamin D deficiency is highly prevalent in patients on dialysis. Although vitamin D deficiency is closely associated with cardiovascular disease (CVD) and high mortality in the general population, the relationship between serum 25-hydroxyvitamin D [25(OH)D] and all-cause and cardiovascular mortality in dialysis patients is uncertain. We aim to explore the relationship between serum25(OH)D levels and allcause and cardiovascular mortality in dialysis patients. Methods. This is a systematic review and meta-analysis of clinical studies among patients receiving maintenance dialysis. We did a systematic literature search in PubMed and Embase to identify studies reporting the relationship between serum 25(OH)D levels and all-cause and cardiovascular mortality in patients on dialysis. The search was last updated on 10 February 2017. Results. The study included 18 moderate to high-quality cohort studies with an overall sample of 14 154 patients on dialysis. The relative risk of all-cause mortality per 10 ng/mL increase in serum 25(OH)D level was 0.78 [95% confidence interval (CI) 0.71 0.86], although there was marked heterogeneity (I2 96%, P < 0.01) that was partly explained by differences in CVD prevalence, baseline parathyroid hormone level and dialysis duration among included studies. The relative risk of cardiovascular mortality per 10 ng/mL increase in serum 25(OH)D level was 0.71 (95% CI 0.63 0.79), with substantial heterogeneity (I2 74%, P 0.004) that was largely explained by differences in study type and serum25(OH)D measurementmethod. Conclusions. In the present study, increased serum 25(OH)D level was significantly associated with lower all-cause mortality and lower cardiovascular mortality in dialysis patients.