Effects of vitamin D or its analogues on the mortality of patients with chronic kidney disease: an updated systematic review and meta-analysis

The objective of this study was to assess whether vitamin D (VD) treatment alters the overall all-cause and cardiovascular mortalities in a chronic kidney disease (CKD) population. We systematically searched PubMed, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials without language restriction, until the publication date of 22 February 2016. All related literatures that compared VD treatment with non-VD treatment and reported the mortality of patients with CKD (including those undergoing dialysis) were identified. Pooled risk ratios (RR) and 95% confidence intervals (CI) were calculated by using the random- and fixed-effects models. Randomised controlled trials (RCTs) that used the intention-to-treat principle and observational studies (OSs) were analysed separately. For this study, 38 studies involving 223 429 patients (17 RCTs, n =1819 and 21 OSs, n =221610) were included. In the OSs, VD treatment was significantly associated with reductions in both all-cause and cardiovascular mortalities; however, such significant association was not found in the RCTs. The existing RCTs do not provide sufficient or precise evidence that VD supplementation affects the mortality of patients with CKD, although subsets of patients that could potentially benefit from VD treatment can be identified by using the existing data from the RCTs. Nevertheless, large-size RCTs are needed in the future to assess any potential differences in survival prospectively.