The Relationship Between Serum Vitamin D Levels And Multiple Sclerosis:A Systematic Review

Objective:To evaluate the relationship between serum vitamin D levels and multiple sclerosis for the purpose of providing scientific evidence for vitamin D supplements in the treatment of Multiple Sclerosis(MS).Methods:Such databases as the Cochrane Library, Pubmed, OVID, EMbase, Central, CNKI,Wan Fang were searched by electronic databases from the date of their establishment to April 2014 and relevant journals such as Chinese Journal of Evidence-Based Medicine,Chinese Journal of Neuroimmunology and Neurology, Chinese Journal of Clinical Neuroscience by manual retrieval to collect the observational studies on the association between vitamin D and MS. According to the method of systematic review provided by the Cochrane Library, two reviewers independently selected literatures, extracted data and assessed the quality of these included studies, then conducted a Meta-analysis on these studies by using Rev Man5.2 software in terms of the inclusion and exclusion criteria of these literatures. We used the fixed or random effects model to test the heterogeneity of these studies. Then we used 95% confidence interval as the evaluation index and made α=0.05 as the size of test.Results:We have collected 13 case-control studies including 923 cases MS patients and 1134 cases controls and 1 cohort study involving 469 cases MS patients. The Newcastle-Ottawa-Scale(NOS) scores in the quality assessment of these studies were abrove 5, indicating more reliable quality. The final results of this Meta-analysis revealed that:(1) in cases of MS group and control group, the serum 25(OH)D levels in the case group were lower than the control group, with significant differences in the two groups[MD=-22.66, 95%CI(-34.26,-11.07), P=0.0001]; further subgroup analysis also showed that the significant differences: the European[MD=-35.58, 95%CI(-66.64,-4.52), P=0.02]and the Asian[MD=-18.03, 95%CI(-23.91,-12.15), P<0.00001]; the differences had no statistical significance after further comparison [MD=-17.55, 95%CI(-48.97, 13.87),P=0.27];(2) in cases of MS relapse and remission group, the serum 25(OH)D levels in the MS relapse group were lower than the remission group, with significant differences between the two groups [MD=-19.14, 95%CI(-26.18,-12.11), P<0.00001];(3) in cases of MS summer and winter group, the serum 25(OH)D levels in the MS summer group were higher than the winter group, with significant differences between the two groups[MD=27.65, 95%CI(7.27, 47.72), P=0.007];(4) in cases of MS group and control group,the serum 1,25(OH)2D levels in the case group were lower than the control group, with significant differences in the two groups [MD=-9.06, 95%CI(-13.86,-4.27), P=0.0002].Conclusions:The present study suggested that the serum25(OH)D levels in the case group were lower than the control group. After further subgroup analysis, the same result in Europe and Asia area was relatively stable, however, there was no obvious difference in the two groups after further comparison. The serum 25(OH)D levels in the MS relapse group were lower than the remission group and the serum 25(OH)D levels in the MS summer group were higher than the winter group.The serum 1,25(OH)2D levels in the case group were lower than the control group. As there were fewer literatures in this study, we needed adopt the studies with large sample size and high quality to further assess the association between vitamin D and MS, which could provide evidence-based medicine for the vitamin D supplements in the treatment of MS.