Marlene Busko

March 04, 2016

PHOENIX, AZ — Moderate consumption of alcohol was associated with a greater risk of having an MI or stroke within hours, but a lower risk of having these outcomes within a day or a week, in a meta-analysis[1]. Heavy drinking, however, was associated with a consistently increased risk of MI or stroke within hours, a day, or a week.

Dr Elizabeth Mostofsky (Beth Israel Deaconess Medical Center, Boston, MA) reported these findings at a poster session here American Heart Association (AHA) Epidemiology and Prevention and Lifestyle and Cardiometabolic Health (EPI|Lifestyle) 2016 Scientific Sessions, and the study was simultaneously published in Circulation.

"Immediately after moderate consumption of alcohol, there is a transient, higher risk of a heart attack or stroke; in that first hour, there is a spike in risk," she told heartwire from Medscape. "But within a day, that association goes away, and in fact it is protective; there's a lower risk of having a heart attack or a hemorrhagic stroke within a day, and within a week there is a lower risk of having an ischemic stroke."

This is among the first studies to shed light on how alcohol consumption is linked with acute cardiovascular outcomes, but it cannot show cause and effect, she cautioned.

Nevertheless, it supports the American Heart Association guidelines that suggest that "if you do drink, do so in moderation," she added, where moderate drinking is defined as one or fewer drinks/day for women and two or fewer drinks/day for men (a drink is 12 oz of beer, 5 oz of wine, or 1.5 oz of spirits, which each contain about 15 g of alcohol).

Risk of MI, Stroke, Soon After Drinking Alcohol

The researchers hypothesized that compared with not drinking alcohol, drinking a moderate amount is associated with an immediate higher risk of cardiovascular events followed by a lower risk of cardiac events after 24 hours, whereas heavy alcohol drinking is associated with an immediate, lasting higher level of cardiovascular risk.

They identified 16 case-control and seven case-crossover studies that looked at alcohol consumption and MI and stroke within a week, which were published from 1987 to 2015 and conducted in Europe (12), New Zealand and Australia (six), the United States (four), and multiple nations (one).

They enrolled 29457 participants and reported on 17,966 cases of MI, 2599 cases of ischemic stroke, and 1262 cases of hemorrhagic stroke. Most studies (20) enrolled men and women, but only six studies presented sex-specific estimates.

Alcohol consumption was mostly assessed in interviews (20 studies) and less often with a questionnaire (three studies).

The studies showed a dose-response effect and a protective effect with moderate drinking, but not heavy drinking.

The relative risk of MI was 0.67 within a day of drinking about two drinks/day (28 g of alcohol), but it was 1.59 within a day of drinking about nine drinks/day (108 g of alcohol), compared with not drinking alcohol.

Drinking about two to four drinks a day was associated with a 30% lower risk of having an MI or hemorrhagic stroke within a day, and drinking about six drinks a week (75 g of alcohol/week) was associated with a 19% lower risk of having an ischemic stroke within a week, compared with not drinking.

However, drinking six to nine drinks a day was associated with a 1.3- to 2.3-fold higher relative risk of having an MI or stroke within a day, and drinking nine to 30 drinks a week was associated with a 2.25- to 6.2-fold higher risk of having an MI or stoke within a week.

"Our dose-response analysis suggests that after 24 hours, moderate drinkers may experience a lower risk of a cardiovascular event compared with other times, whereas heavy drinking is associated with a higher risk even after 24 hours," Mostofsky and colleagues write.

Prior studies in men have shown that drinking, for example, one to two drinks a day, four days/week lowers cardiovascular risk more than drinking the same amount in fewer days.

"Therefore, it is possible that over time individuals who frequently drink small amounts of alcohol may experience a temporarily heightened risk, but this may be offset in part by the subsequent protective benefits in the hours after consumption, whereas consuming large amounts of alcohol at once may result in both a sharply higher immediate risk, and repeated bouts cause a higher long-term risk," they suggest.

Invited to comment, Dr Ana Baylin (University of Michigan School of Public Health, Ann Arbor) noted that the participants had had a heart attack or stroke and then were asked about their recent alcohol intake. "Although there is a lot of research on the chronic effects of alcohol, there is not much on the acute effects, and this study has tried to summarize that scarce literature and therefore has filled a gap in the literature," she said.

More research is needed to determine whether the acute effect of alcohol differs by ethnicity, gender, or genetic background, since, for example, the protective effect of moderate, chronic alcohol intake is mostly seen in populations of European origin, but not in Asians. "These are very important questions that remain unanswered," according to Baylin.

The authors have no relevant financial relationships.

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