If consumed in moderation, alcohol could protect against heart attack and stroke - but not in the first few hours after consumption.
Lead study author Elizabeth Mostofsky, of the Harvard T.H. Chan School of Public Health in Boston, MA, and colleagues publish their findings in the journal Circulation.
The team also recently presented their results at the American Heart Association's Epidemiology and Prevention/Lifestyle 2016 Scientific Sessions in Phoenix, AZ.
While previous studies have investigated the longer-term cardiovascular risks associated with moderate and heavy alcohol intake, the authors note that less is known about the immediate effects of alcohol consumption.
"Ours is the first to synthesize all the available information to gain new knowledge on the acute risk of heart attacks and strokes in the hours after drinking and the risk in the following week for different amounts of alcohol consumed," says Mostofsky.
The team conducted a systematic review and meta-analysis of 23 studies that included almost 30,000 participants.
The alcohol intake of participants was assessed, and the researchers monitored the incidence of heart attack and stroke in the hours and days following alcohol consumption.
Moderate drinking reduces risk of heart attack, stroke after 24 hours
The team found that the risk of heart attack and stroke increased immediately after a single dose of alcohol; heart rate increases within 1-3 hours of drinking, blood pressure increases and blood platelets become stickier, says Mostofsky.
Heavy drinkers were found to have both a short- and long-term risk of heart attack and stroke; those who consumed six to nine drinks in a day were at almost double the risk, while those who consumed 19-30 drinks in a week were at six times higher risk for heart attack and stroke.
While participants who engaged in moderate drinking - defined as up to six drinks a week in the study - were found to have an immediate increased risk of heart attack and stroke, this subsided within 24 hours.
The researchers explain that moderate alcohol intake improves blood flow and blood vessel function and reduces clotting after 24 hours, lowering the risk of heart attack and stroke.
Commenting on the findings, Mostofsky says:
"There appears to be a transiently higher risk of heart attack and strokes in the hours after drinking an alcoholic beverage but within a day after drinking, only heavy alcohol intake seems to pose a higher cardiovascular risk.
[...] regularly drinking small amounts of alcohol in the long term appears to both increase levels of HDL cholesterol (high-density lipoprotein cholesterol), the so-called good cholesterol, and reduce the tendency to form blood clots. If you drink alcohol, do so in moderation."
Last month, Medical News Today reported on another study hailing the potential heart benefits of moderate drinking, in which researchers suggest that three to five drinks a week could reduce the risk of heart attack and heart failure.