Vitamin B12, folate, and homocysteine levels and multiple sclerosis: A meta-analysis.

Background: Multiple sclerosis (MS) is a demyelinating and disabling inflammatory disease of the central nervous system. Several factors contribute to MS pathogenesis including genetic-environmental interactions. Case-control studies suggest that there might be associations between MS and homocysteine (Hcy), vitamin B12, and folate blood levels.

Aim: To meta-analyze all available data describing associations between MS and serum or plasma Hcy, vitamin B12, and folate levels.

Methods: The PubMed, MEDLINE, and EMBASE databases were searched for eligible case-control studies published until June 2017. After data extraction, separate analyses using mainly random-effects models were conducted to test for associations between MS and vitamin B12, Hcy, or folate blood levels.

Results: Twelve, 12, and 9 studies met the inclusion criteria for meta-analysis of MS and Hcy, vitamin B12, and folate levels, respectively. The standardized mean difference (SMD) between MS patients and controls was statistically significant for Hcy (SMD: 0.70, 95% CI: 0.06, 1.34). Stratification according to clinical pattern did not reveal significant differences between relapsing-remitting MS patients and controls (SMD: 0.30, 95% CI: -0.93, 1.54) or between secondary progressive MS patients and controls (SMD: 0.12, 95% CI: -1.65, 1.90). There were no significant differences in SMD between MS patients and healthy individuals for vitamin B12 (SMD: -0.09, 95% CI: -0.29, 0.10) or folate (SMD: -0.06, 95% CI: -0.17, 0.05).

Conclusion: MS patients tend to have elevated Hcy blood levels compared to healthy controls. Hcy may contribute to the pathogenesis of the disease.