Light drinking may protect against death after myocardial infarction

Following an episode of myocardial infarction (MI), patients with light or moderate alcohol consumption appear to have a lower risk of mortality than nondrinkers, according to a study.

“These … findings should be interpreted with caution in light of the total evidence on alcohol use and health, also taking into account the potential social harms of alcohol intake,” the researchers said.

Some 4,365 patients (aged 60‒80 years, 79 percent male) with an MI ≤10 years before study enrolment were included in this analysis. The researchers used a 203-item food frequency questionnaire to evaluate alcohol (total ethanol) and dietary intakes over the past month.

Patients were classified as follows: nondrinkers (0 g/d; n=956) or very light (>0 to 2 g/d; n=385), light (male: >2 to 10 g/d; female: >2 to 5 g/d; n=1,125), moderate (male: >10 to 30 g/d; female: >5 to 15 g/d; n=1,207), or heavy drinkers (male: >30 g/d; female: >15 g/d; n=692).

Using Cox models, the researchers obtained hazard ratios (HRs) of mortality for alcohol intake, adjusting for age, sex, education, smoking, body mass index, physical activity, and dietary factors.

Of the participants, 83 percent of males and 61 percent of females consumed alcohol. A total of 2,035 deaths occurred during approximately 12 years of follow-up; of these, 903 were from cardiovascular disease (CVD) and 558 from ischaemic heart disease (IHD). [Am J Clin Nutr 2022;115:633-642]

In comparison to the combined reference group of nondrinkers and very light drinkers, HRs for all-cause mortality were 0.87 (95 percent confidence interval [CI], 0.78‒0.98) for light, 0.85 (95 percent CI, 0.75‒0.96) for moderate, and 0.91 (95 percent CI, 0.79‒1.04) for heavy drinkers.

The HRs for CVD mortality were 0.80 (95 percent CI, 0.67‒0.96) for light, 0.82 (95 percent CI, 0.69‒0.98) for moderate, and 0.87 (95 percent CI, 0.70‒1.08) for heavy drinkers. For IHD mortality, the findings were comparable.

HRs remained virtually unchanged when using nondrinkers or very light drinkers alone as the reference and after excluding former drinkers or patients with diabetes or poor/moderate self-rated health.

In previous cohort studies, the lower risk of death was highly debated, with potential residual confounding because of incomplete adjustments for socioeconomic status and lifestyle factors. [BMJ 2011;342:d671; Nutr Metab Cardiovasc Dis 2019;29:1003-1008]

In the present analysis, adjustments were made for potential confounders. Reporting bias could still occur in cohort studies, with heavy drinkers being misclassified in the nondrinking reference category.

“We therefore repeated our analysis in drinkers only, using patients with the lowest alcohol intake as the reference group,” the researchers said. “This yielded similar inverse associations for all-cause, CVD, and IHD mortality, although the findings were no longer significant due to a smaller sample size.”

Alcohol benefits and harms

Intake of alcohol could induce positive changes in the cardiovascular system, such as improved blood lipid profile, adiponectin elevation, plasma fibrinogen reduction, and a lower endocrine response to stress, which would deliver a cardioprotective effect. [BMJ 2011;342:d636; Stress 2013;16:369-376]

In contrast, alcohol elevates blood pressure, a major risk factor for CVD, and raises the risk of atrial fibrillation. [J Epidemiol Community Health 2019;73:796-801; J Epidemiol Community Health 2019;73:796-801; Eur Heart J 2021;42:1170-1177]

In addition, alcohol harms the liver and brain, contributes to the development of cancers, and increases the risk of injuries. Misuse of alcohol may also result in social harm. [Lancet North Am Ed 2009;373:2223-2233; Lancet North Am Ed 2018;392:1015-1035]

“Therefore, even if a protective effect of alcohol intake against CVD were present, minimizing the intake of alcohol may be recommended,” the researchers said.