Vitamin B supplementation, homocysteine levels, and the risk of cerebrovascular disease: a meta-analysis.

OBJECTIVE: To perform a meta-analysis on the effect of lowering homocysteine levels via B vitamin supplementation on cerebrovascular disease risk.
METHODS: Using clinical trials published before August 2012 to assess stroke events, we used relative risks (RRs) with 95% confidence intervals (95% CIs) to measure the association between B vitamin supplementation and endpoint events using a fixed-effects model and χ(2) tests. We included 14 randomized controlled trials with 54,913 participants in this analysis.
RESULTS: We observed a reduction in overall stroke events resulting from reduction in homocysteine levels following B vitamin supplementation (RR 0.93; 95% CI 0.86-1.00; p = 0.04) but not in subgroups divided according to primary or secondary prevention measures, ischemic vs hemorrhagic stroke, or occurrence of fatal stroke. There were beneficial effects in reducing stroke events in subgroups with ≥3 years follow-up time, and without background of cereal folate fortification or chronic kidney disease (CKD). Some trials that included CKD patients reported decreased glomerular filtration rate with B vitamin supplementation. We conducted detailed subgroup analyses for cyanocobalamin (vitamin B12) but did not find a significant benefit regarding intervention dose of vitamin B12 or baseline blood B12 concentration. Stratified analysis for blood pressure and baseline participant medication use showed benefits with >130 mm Hg systolic blood pressure and lower antiplatelet drug use in reducing stroke risk.
CONCLUSIONS: B vitamin supplementation for homocysteine reduction significantly reduced stroke events, especially in subjects with certain characteristics who received appropriate intervention measures.