A new, wide-ranging study says heavy drinking -- more than 60 grams, or five shots of hard liquor a day -- increases the risk of stroke by more than 60 percent, compared to those who don't drink at all.
But lighter drinking -- less than 12 grams, or one shot a day -- reduced the risk of stroke by 20 percent, compared to teetotalers.
To arrive at those numbers, researchers at the Tulane University School of Public Health and Tropical Medicine gathered 122 studies that examined the health benefits and hazards of alcohol and settled on 35 that focused on drinking and stroke.
Compared to non-drinkers, heavy drinkers had a 69 percent greater risk of ischemic stroke, the kind that occurs when a clot blocks blood flow to the brain. And the heavy drinkers had about double the risk of hemorrhagic stroke, which happens when a blood vessel in the brain bursts.
However, those who consumed less than one shot a day reduced their risk of ischemic stroke by 20 percent, compared to teetotalers.
And those who drank two or three shots a day had a 28 percent reduction in risk of ischemic stroke, compared to abstainers, says the study, which appears in the Feb. 5 Journal of the American Medical Association.
The researchers' numbers come from a "meta-analysis" of the 35 studies -- a sophisticated mathematical method of summing up multiple findings, says lead author Kristi Reynolds, a graduate research student at Tulane. The analysis was done, she says, because there have been conflicting results from studies about the relationship between drinking alcohol and stroke risk.
"Some studies have shown alcohol to be both a risk factor and a protective factor, and some have found it increases the risk of both hemorrhagic and ischemic stroke," she says. This new report clarifies alcohol's benefits and risks, she adds.
Dr. Robert H. Eckel is professor of medicine at the University of Colorado Health Sciences Center and chairman of the American Heart Association's scientific council on nutrition, physical activity and metabolism.
Eckel recently told HealthDay: "The American Heart Association is aware of the potential benefits of alcohol."
The association is also aware of the potential dangers of drinking, he said. Among the health threats listed on the heart association's Web site are high blood pressure, heart failure and excessive calorie intake that can lead to obesity, a major risk factor for stroke and other cardiovascular diseases.
"If you look at alcohol as a drug, the potential adverse effects would be sufficient enough to limit its use," Eckel said.
The heart association does not encourage any abstainer to take up drinking because of its possible beneficial effects. "We encourage adults to discuss the use of alcohol with their physicians," Eckel said.
You can learn more about alcohol and cardiovascular disease from the American Heart Association. To learn more about stroke, visit the National Institute of Neurological Disorders and Stroke.