Despite these findings, Hankey isn't sure that B vitamins don't work. "Our study may well have been underpowered statistically," he said.
Had the trial gone on longer, a "significant treatment effect may have emerged, and has thus been missed in our study," Hankey added.
"I don't think it is the end of the road for B vitamins in stroke prevention. We need to see the effect of B vitamins in the three other ongoing trials, particularly in patients who have been treated for several years, and particularly in patients with stroke caused by small vessel intracranial disease," he added.
Dr. Larry B. Goldstein, director of the Duke Stroke Center at Duke University Medical Center, agreed that the question of whether or not B vitamins lower the risk of a second stroke or heart attack was not answered fully by this trial.
"High homocysteine is associated with both stroke and coronary heart disease. Homocysteine can be lowered with B-complex vitamin supplements, but whether doing so lowers the risk of vascular events is uncertain," Goldstein said.
Earlier studies found no benefit of homocysteine lowering in subjects with coronary heart disease or renal failure. "The VISP trial, conducted in North America, found no benefit of B-vitamin treatment in subjects with prior stroke, but had several important methodological limitations," Goldstein added.
This new report also finds no benefit of treatment with B-complex vitamins in patients with stroke or TIA, but the adverse event rates in both the treatment and placebo groups were lower than anticipated, he pointed out.
"A benefit by as much as an 18 percent reduction in risk remains possible," Goldstein said. "Treatment with B vitamins appeared safe, and the results of other ongoing trials should help more definitively answer the question."
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