Efficacy of homocysteine-lowering therapy with folic Acid in stroke prevention: a meta-analysis.

BACKGROUND AND PURPOSE Although a lower serum homocysteine concentration is associated with a reduced risk of stroke in epidemiologic studies, randomized, controlled trials have yielded mixed findings regarding the effect of therapeutic homocysteine lowering on stroke prevention. We performed a meta-analysis of randomized, controlled trials to assess the efficacy of folic acid supplementation in the prevention of stroke. METHODS Salient trials were identified by formal literature search. Relative risk (RR) with 95% CI was used as a measure of the association between folic acid supplementation and risk of stroke, after pooling data across trials in a fixed-effects model. RESULTS The search identified 13 randomized, controlled trials that had enrolled 39 005 participants for folic acid therapy to reduce homocysteine in which stroke was reported as an outcome measure. Across all trials, folic acid supplementation was associated with a trend toward mild benefit that did not reach statistical significance in reducing the risk of stroke (RR=0.93; 95% CI, 0.85-1.03; P=0.16). The RR for nonsecondary prevention trials was 0.89 (95% CI, 0.79-0.99; P=0.03). In stratified analyses, a greater beneficial effect was seen in the trials testing combination therapy of folic acid plus vitamins B6 and B12 (RR=0.83; 95% CI, 0.71-0.97; P=0.02) and in the trials that disproportionately enrolled male patients (men:women >2; RR=0.84; 95% CI, 0.74-0.94; P=0.003). CONCLUSIONS Folic acid supplementation did not demonstrate a major effect in averting stroke. However, potential mild benefits in primary stroke prevention, especially when folate is combined with B vitamins and in male patients, merit further investigation.