(July 2001)

Two articles, one appearing early and one late in 1999, received a lot of publicity. Each was authored by well-respected investigators (from Columbia and Harvard Medical Schools). Each was published in prestigious journals (The Journal of the American Medical Association and The New England Journal of Medicine).

The earlier study compared 677 patients with stroke due to reduced blood supply to the brain (ischemic stroke) with 1,139 controls. Those consuming up to two alcoholic drinks a day had roughly a 50 percent reduction in risk of ischemic stroke. When the frequency of alcohol intake was analyzed in detail, the biggest reduction in risk of stroke was found in those who drank less than one alcoholic drink a month. Almost the same protection was found for those who drank an alcoholic beverage at least every month, but not every day. Some protection was even found for those who consumed two to four drinks a day. Only those who consumed five or more drinks a day showed an increased risk that was, however, not statistically significant. It did not seem to matter whether the alcoholic beverage drunk was wine, beer, or liquor; all were protective.

The second study followed 22, 071 male physicians, ages 40 to 84 years, for an average of 12 years. During that period, 679 strokes occurred; most were the ischemic (reduced blood supply) type, but 88 were of the hemorrhagic type. For both types, a 16 percent reduction in risk occurred for those who drank one or more alcoholic beverages each week; even though the benefit appeared equal in ischemic and hemorrhagic strokes, the authors said that, after taking other factors into account, the reduction in ischemic stroke was statistically significant, whereas the equal benefit for hemorrhagic stroke was not.

Approximately equal benefit was found for those who drank one alcoholic drink a week as those who consumed one or more drinks a day.

Both studies conclude that "moderate" alcohol intake reduces the risk of stroke.

Commentary: First, it should be noted that, if all the available studies are taken together, there is about an even split between those that find moderate alcohol consumption is protective against particularly ischemic stroke and those that find no such protection. So, there is no convergence of the data - and that disagreement among the studies is critical in making or not making recommendations. There is general agreement that heavy alcoholic use (more than four alcoholic drinks a day) increases the risk of hemorrhagic stroke.

Second, there is a big difference in the extent of the alleged protection between the two studies; one found about a 50 percent reduction in risk, the other less than 20 percent. That is a very substantial difference.

Third, and most critical, in coming to a conclusion about these two studies is the observation that, in one study, even those consuming less than one drink a month and in the other only one drink a week, had equal benefits to those drinking several times a week or daily. Think of it - have a glass of wine every month or two and cut your stroke risk in half. That does not make much sense.

Fourth, the investigators in both studies have a hard time figuring out mechanisms that would account for the alleged benefit. Alcohol taken once a week or less has only short-term effects in non-pregnant adults. One of the papers suggests the explanation may lie in changes in blood cholesterol subgroups (lipoproteins), but that would be like taking a cholesterol-lowering drug once a week or once a month and expecting good results. The likelihood of a drink a week or once a month improving blood lipid profile (raising so-called good cholesterol, or lowering dangerous components of cholesterol) is very unlikely.

Until investigators can show us a valid mechanism for one drink a week or one every month or two reducing the risk of stroke, these studies should be regarded with a large dose of skepticism.

In contrast, the evidence that one or two drinks a day can moderately reduce the risk of coronary heart disease and heart attacks is quite good and the major mechanisms explaining the protection are pretty well established.

Sacco, R.L., et al. The protective effect of moderate alcohol consumption on ischemic stroke. Journal of the American Medical Association. Vol 281. (January 6). Pgs 53-60. 1999.

Berger, K., et al. Light to moderate alcohol consumption and the risk of stroke among U.S. male physicians. The New England Journal of Medicine. Vol 341. (November 18) Pgs 1557-1564. 1999.