Happy hour may not be so happy afterward, as researchers have found that stroke risk is more than twice as high the hour immediately after consuming alcohol, even after as little as one drink.
Still, health experts say, that's no reason to put down the wine glass or beer mug because there's a significant body of research showing that moderate alcohol intake can be good for you. Numerous studies have shown that drinking alcohol in moderation has beneficial effects on the cardiovascular system.
"Overall, the long-term stroke risk may be lower among persons who consume small to moderate amounts of alcohol (no more than two drinks per day for men and no more than one drink for non-pregnant women)," Dr. Larry Goldstein, professor of medicine and director of the Duke Stroke Center at Duke University Medical Center in Durham, N.C., wrote in an e-mail. "Therefore, the long-term reduction may outweigh the immediate risk."
Researchers from the Harvard School of Public Health and Beth Israel Deaconess Medical Center in Boston looked at nearly 400 men and women who suffered ischemic strokes and compared their alcohol intake in the previous year to their intake in the hour before their stroke symptoms began. They found that stroke risk was 2.3 times higher during the hour after drinking than it was when there was no alcohol consumed.
The risk was the same for different kinds of alcoholic beverages. This risk decreases by about 30 percent within 24 hours.
The researchers also said they did not include people who smoked, drank a caffeinated beverage or were exposed to other potential stroke triggers in the hour before stroke symptoms began.
"Even when we excluded people who were exposed to another risk factor in that hour, there was no change in effect," said Elizabeth Mostofsky, a co-author and doctoral candidate at the Harvard School of Public Health.
Some experts, though, questioned the study's methodology.
Asking study participants to remember certain things is "notorious for introducing recall bias," said Dr. George Newman, chairman of neurosensory sciences at Albert Einstein Medical Center in Philadelphia.
Dr. Cathy Sila, professor of neurology at Case Western Reserve University School of Medicine in Cleveland, said, "Most of the information is obtained from interviews and relies on individuals reporting their intake accurately," which is inherently unreliable.
Harvard's Mostofsky also said the study did not look at the effects of different amounts of alcohol or thoroughly evaluate the impact different kinds of alcoholic beverages could have. Additionally, the study only examined the transient effects of minor strokes, not severe or fatal ones.
"It's also a small study, and it requires a large clinical trial," she added.
Regardless of the study's flaws, Mostofsky said the most important finding was that this hour-long elevated stroke risk may be offset by the benefits of moderate alcohol intake.
"But we don't have the evidence to say that people who drink in moderation should stop or start," she said.
Other experts agreed.
"For now, 'all things in moderation,' and I would not recommend to anyone that they stop drinking because of this study," said Dr. Patrick Lyden, chair of the department of neurology at the University of California, San Diego School of Medicine.