Binge-drinking at least six cocktails in one night may increase the risk of cardiovascular complications like heart attacks and strokes over the following week, a research review suggests.
Even one drink was associated with higher odds of cardiovascular problems over the next 24 hours compared to teetotalers, the analysis also found.
After that, however, moderate drinkers who indulge in two to four adult beverages may actually experience a lower risk of heart attacks and strokes over the next week than their friends who drink nothing at all.
"The impact of alcohol on your risk of heart attacks and strokes depends on how much and how often you drink," said lead study author Elizabeth Mostofsky of the Harvard T.H. Chan School of Public Health in Boston.
"Habitual moderate alcohol consumption is associated with lower risk of heart disease in both sexes, but the amount of alcohol associated with cardiovascular benefits is lower among women than among men," Mostofsky added by email. "This is consistent with public health recommendations that advise consumption of no more than two drinks per day for men and no more than one drink per day for non-pregnant women."
While previous research has linked moderate drinking to a lower risk of heart attacks over time, the current analysis focused on what happens in the first days after imbibing based on how much alcohol people consumed.
To explore how the amount of alcohol influenced the odds of heart attacks and strokes, Mostofsky and colleagues analyzed data from 23 studies published between 1987 and 2015 that, combined, had a total of 29,457 participants.
Across all the studies, there were 17,966 heart attacks and 2,599 ischemic strokes, the most common type that results from an obstruction in a blood vessel supplying the brain. There were also 1,262 hemorrhagic strokes, the rarer type that occur when a blood vessel bursts.
When people had about two to four drinks, after 24 hours they had about a 30 percent lower risk of heart attacks and hemorrhagic strokes than their abstaining peers, researchers report in the journal Circulation.
These moderate drinkers also had a 19 percent lower risk of ischemic strokes within a week than people who consumed no alcohol at all, the study also found.
In contrast, binges of six to nine drinks were associated with a 30 percent higher risk of cardiovascular events the next day.
Immediately after alcohol consumption, the body has both good and bad physiologic responses, the researchers note. Among other things, one drink can increase the heart rate and cause electromechanical problems in heart function within one to three hours.
But by 12 to 24 hours, having about two drinks can be associated with improved blood flow and other beneficial changes in the cardiovascular system, the authors also point out.
Habitual moderate drinking is also associated with improvements in cardiovascular risk factors like cholesterol levels, heart rate and the ability to process blood sugars.
Heavy drinking, however, is linked to an elevated risk of hypertension, diabetes, cardiovascular disease, strokes and death after a heart attack, the researchers explain.
Limitations of the analysis include the lack of data on regular heavy drinking episodes and the potential for underlying medical conditions of participants in some of the studies to influence the relationship between alcohol and cardiovascular disease. They also lacked data on effects of different types of alcohol like wine versus beer.
The take-home message is multi-faceted, said Giuseppe Lippi, a researcher at the University of Verona in Italy who wasn't involved in the study.
"Heavy alcohol consumption must always be avoided, not only for the risk of cardiovascular disease, but also because it causes acute injury to the liver and to the central nervous system," Lippi said by email.
"Moreover, especially with binge drinking, the risk of car accidents increases by many folds," Lippi added. "On the other hand, drinking 2-3 drinks, especially red wine, is good for the health."