Association between serum vitamin D levels and the risk of kidney stone: evidence from a meta-analysis

BACKGROUND Many epidemiological studies have conducted to evaluate the association between serum vitamin D levels and the risk of kidney stone. The aim of this study was to summarize the evidence from epidemiological studies between them. METHODS Pertinent studies were identified by a search of PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI) and China Biology Medical literature up to July 2015. Standardized mean difference (SMD) was conducted to combine the results. Random-effect model was used. Publication bias was estimated using Egger's regression asymmetry test. RESULTS Seven articles involving 451 kidney stone cases and 482 controls were included in this meta-analysis. Our pooled results suggested that kidney stone patients had a significantly higher serum vitamin D level compared with controls [summary SMD = 0.65, 95 % CI = 0.51, 0.79, I(2) = 97.0 %]. The associations were also significant both in Europe [SMD = 0.35, 95 % CI = 0.17, 0.53] and in Asia [SMD = 1.00, 95 % CI = 0.76, 1.25]. No publication bias was found. CONCLUSIONS Our analysis indicated that serum vitamin D level in kidney stone patients was significantly higher than that in non-kidney stone controls, both in Europe and Asia populations.