Alcohol and Heart Disease: AHA Calls for Stricter Guidance

In a recent scientific statement published in Circulation, the American Heart Association (AHA) summarizes current evidence on the relationship between alcohol use and cardiovascular health, emphasizing that the effects of alcohol are complex, dose-dependent, and influenced by multiple factors. The authors recommend increased screening for alcohol use in clinical practice and call for more rigorous, unbiased research to clarify alcohol’s actual cardiovascular impact.

“Although excessive alcohol use is a leading preventable cause of chronic medical conditions, low to moderate alcohol consumption (eg, no more than 1 to 2 drinks a day) has been hypothesized to confer a cardioprotective effect by reducing the risk of several forms of CVD,” wrote the statement authors.

While some observational studies have suggested protective associations with low levels of alcohol consumption, the statement underscores the significant limitations of observational research and notes that such findings are being challenged by research implementing new methodologies, such as individual participant-level data meta-analysis and Mendelian randomization. It also highlights the established links between alcohol and elevated blood pressure, atrial fibrillation, and cardiomyopathy.

“More randomized trials of low to moderate alcohol consumption are needed for more definitive conclusions. In stark contrast, heavier alcohol consumption, such as binge drinking or consuming on average three or more drinks per day, is consistently associated with worse outcomes in every cardiovascular disease entity studied,” wrote the authors.

Alcohol consumption has been shown to affect blood pressure in a dose-dependent and time-sensitive manner. While consuming one or two drinks typically has no short-term effect, consuming three or more drinks leads to an initial drop in blood pressure, followed by a significant increase within 24 hours. Meta-analyses have shown that drinking three or more drinks/day raises both systolic and diastolic blood pressure compared with no or less drinking and that reducing intake from heavy levels (≥6 drinks/day) leads to meaningful blood pressure reductions. Long-term cohort studies confirm a linear relationship between alcohol use and increased risk of hypertension, even at lower levels of consumption.

Studies examining alcohol use and coronary artery disease (CAD) have shown mixed results, with outcomes varying by drinking patterns, definitions of CAD, and study design. Observational studies often suggest a lower risk of myocardial infarction with low to moderate alcohol consumption, particularly under US Dietary Guidelines for Americans limits, but these findings are prone to bias and confounding. In contrast, Mendelian randomization studies do not support a protective effect, showing no significant association between genetically predicted alcohol intake and CAD risk. Importantly, binge or heavy episodic drinking appears to negate any potential benefit of low to moderate intake on CAD risk.

Evidence from both observational and Mendelian randomization studies indicates that heavy alcohol consumption (>4 drinks/day) increases the risk of all types of stroke. While some observational studies suggest that low to moderate alcohol use (≤2 drinks/day) may modestly lower the risk of ischemic stroke, the evidence is currently considered insufficient to draw definitive conclusions about the relationship. Among current drinkers, stroke risk increases in a dose-dependent manner, with even small increases in alcohol intake associated with higher risks of ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage.

Heavy alcohol consumption is consistently associated with an increased risk of atrial fibrillation. The risk appears to rise in a linear fashion, but no clear threshold effect has been identified. Abstaining from alcohol has been shown to reduce atrial fibrillation burden. Alcohol has been associated with physiological changes, such as atrial enlargement and fibrosis, that could underlie its arrhythmogenic effects. In contrast, there is no strong or consistent evidence that alcohol significantly influences the risk of supraventricular tachycardia, ventricular arrhythmias, or bradycardias.

“Long-term excessive alcohol use is associated with the development of a dilated left ventricle, normal or reduced left ventricular wall thickness and mass, and, in advanced stages, [heart failure (HF)] with reduced left ventricular ejection fraction,” explained the authors.

Long-term excessive alcohol use is a well-established cause of alcoholic cardiomyopathy (ACM). While the exact threshold for alcohol-induced cardiomyopathy is unclear, sustained intake of 7-15 drinks per day over 5-15 years is associated with adverse changes in systolic or diastolic ventricular function. Some genetic factors may predispose individuals to ACM, and women appear to be at risk of developing ACM with lower alcohol exposure than men.

Regarding HF, observational studies have suggested a possible protective effect of low-level drinking (<1–2 drinks/day), but Mendelian randomization studies do not support this and indicate increased HF risk, especially with higher consumption (>7-10 drinks/week). In people with pre-existing structural heart abnormalities, even moderate alcohol consumption (≥5 drinks/week) may significantly increase the risk of symptomatic HF progression.

“The overwhelming evidence demonstrates that heavy (generally >2 drinks[ per day]) and binge alcohol consumption is harmful to cardiovascular health. Abstinence and reducing alcohol intake may lower the risk for certain cardiovascular conditions such as hypertension,” concluded the authors. “Uncertainty remains about the true cardiovascular risk of drinking lightly, such as one to two drinks [per day]. Multiple unknowns persist, providing opportunities for important research into the effects of this commonly consumed substance.”

Given the current evidence, the authors advise that clinicians “should reinforce healthy lifestyle behaviors such as regularly engaging in physical activity, avoiding tobacco use, and maintaining healthy body weight,” and call for more research, especially randomized clinical trials “to better elucidate the true health effects of light to moderate alcohol consumption.”