Reducing heavy alcohol intake: a lifeline for cardiovascular health

Can reducing heavy alcohol intake significantly lower cardiovascular risk, or is the damage already done?

Peter Attia

Read Time 7 minutes

Excessive alcohol consumption is a pervasive behavior, often with significant implications for both personal and public health. While we’ve recently covered the ongoing debate about the health effects of low-to-moderate alcohol consumption, heavy alcohol consumption is a well-established risk factor for numerous adverse health outcomes, including major adverse cardiovascular events (MACE). 

The wealth of evidence supporting a causal link between heavy alcohol use and cardiovascular disease certainly might motivate some to reduce their intake, but for many with a long history of heavy drinking, there is a perception that the “damage is already done,” such that any attempt at reducing intake would prove pointless. Thus, understanding and defining the exact impact of changes in drinking habits on cardiovascular health is crucial. Recent research by Kang et al. investigated just this question¹: can reducing heavy alcohol intake to mild, or even moderate levels, significantly lower cardiovascular risk, or is the “damage already done”?

Study overview

This cohort study explored the impact of reducing alcohol consumption on the risk of MACE in individuals with a history of heavy drinking using data from the Korean National Health Insurance Service–Health Screening (NHIS-HEALS) database, which includes information on demographics, medical histories, lifestyles, and laboratory results from a large, representative sample of the South Korean population. 

The study analyzed data from 21,011 individuals aged 40 to 79, all of whom met criteria for “heavy drinking” – defined as consuming >4 drinks (56 grams) per day or >14 drinks (196 grams) per week for males, and >3 drinks (42 grams) per day or >7 drinks (98 grams) per week for females – over a preliminary health examination period (2005-2008). In a second health examination period (2009-2012), participants were then divided into two groups based on whether they continued to meet the criteria for heavy drinking (sustained heavy drinking) or reduced their alcohol consumption to mild-to-moderate levels – defined as up to 4 drinks (56 grams) per day or up to 14 drinks (196 grams) per week for males, and up to 3 drinks (42 grams) per day or up to 7 drinks (98 grams) per week for females. Alcohol consumption levels were assessed using self-report questionnaires administered during health examinations. 

The primary outcome of interest was the occurrence of MACE, which encompassed nonfatal myocardial infarction, angina (chest pain) requiring revascularization, any stroke, and all-cause mortality. Moreover, the authors analyzed and controlled for age, sex, body mass index (BMI), smoking status, physical activity level, and the presence of medical comorbidities such as hypertension, diabetes, dyslipidemia, and chronic kidney disease.

Key findings 

Over the follow-up period of 162,378 person-years, participants who reduced their alcohol consumption exhibited a 23% lower risk of MACE compared to those who continued heavy drinking (HR=0.77; 95% CI: 0.67-0.88). In addition to the primary composite outcome, the researchers also examined risk of individual conditions included under the MACE umbrella and likewise noted lower risk for many of these conditions among those who had reduced their alcohol intake. Specifically, participants who reduced their drinking experienced a 30% decrease in risk of angina (HR=0.70; 95% CI: 0.51-0.97), a 34% decrease in risk of ischemic stroke (HR=0.66; 95% CI: 0.51-0.86), a 28% decrease in risk of any stroke (HR=0.72; 95% CI: 0.57-0.91), a 29% decrease in risk of coronary artery disease (HR=0.71; 95% CI: 0.52-0.98), and, finally, a 21% decrease in risk of all-cause death (HR=0.79; 95% CI: 0.66-0.96). However, similar benefits of reducing alcohol intake were not observed for hemorrhagic stroke and nonfatal MI, which authors Kang et al. suggested might, in theory, be explained by changes in platelet function and coagulation factors linked with moderate alcohol consumption, potentially increasing the risk of hemorrhagic events.

Still, overall these results tell an encouraging story: even for those with a history of heavy drinking, reducing alcohol intake can lead to substantial cardiovascular benefits.

Some biases might inflate the apparent effect size…

The study is not without significant limitations. The observational nature of the study means that causality can’t be definitively established. Although the time-exposure design strengthens the association between reduced alcohol consumption and improved cardiovascular outcomes, it does not eliminate the possibility that confounding factors might have influenced results. For instance, individuals who consume alcohol heavily often lead a more sedentary lifestyle and are more likely to smoke and have a poor diet, potentially exerting a substantial influence on cardiovascular health. 

Likewise, individuals who decide to reduce their alcohol intake may also be making other health-conscious decisions simultaneously. For example, a person who cuts down on drinking might also adopt a healthier diet, increase their physical activity levels, or stop smoking – all behaviors with well-documented impacts on cardiovascular health. Since a person who chooses to drink less is also likely to engage in other healthy behaviors – and because these factors can independently affect cardiovascular health – other lifestyle changes might confound the observed association between reduced alcohol consumption and MACE. In fact, when examining the baseline characteristics between the groups, it becomes evident that the group that ultimately continued to drink heavily was less healthy at baseline in terms of the several lifestyle-associated aspects than those who subsequently reduced their intake – with higher rates of obesity (42.5% vs. 38.6%) and greater fraction of participants currently smoking (40.1% vs. 31.6%). This observation supports the idea that those who reduced their alcohol consumption were already engaging in some other healthier behaviors than their sustained-drinking counterparts.

Despite rigorous statistical adjustments, accounting for these interconnected behaviors and their individual contributions to health outcomes is challenging. This is further complicated by the fact that observational studies often rely on self-reported data for these lifestyle factors, which can also bias the data, especially if participants are asked to recall their drinking habits over a long period. Variability and potential for inaccuracy are inherent in self-reported data and can affect the study’s outcomes.

…While other biases might detract from it 

On the other hand, other biases might lead to an underestimation of the association between reduced alcohol intake and lower MACE risk to an extent. For instance, self-reporting is more likely to result in participants underreporting, rather than overreporting, their alcohol intake in order to align with social norms that discourage heavy drinking. The resulting underestimation of actual alcohol intake could thus lead to underestimation of the cardiovascular benefits associated with reducing alcohol consumption. Consequently, the study’s outcomes and conclusions might not fully capture the extent of the health improvements experienced by those who genuinely reduced their drinking.

Additionally, it’s probable that some of those who reduced their alcohol intake did so because of other cardiovascular risk factors placing them at higher risk – including factors which may have developed or come to light after baseline data were taken. In order to ensure that the observed effects on cardiovascular outcomes were more accurately attributable to changes in alcohol consumption levels (from heavy to mild-to-moderate) rather than to other health conditions that might have led participants to quit drinking (i.e., the “sick-quitter” effect), the investigators excluded individuals who completely abstained from alcohol drinking during the follow-up period were excluded. However, this exclusion did not account for those who may have simply reduced their drinking (rather than ceasing completely) in response to revelations about emerging health issues or other risk factors or markers for cardiovascular disease (CVD). 

In other words, causality was likely reversed in a subset of individuals who, despite reducing their drinking, likely had a higher risk for CVD events due to pre-existing health conditions not included in baseline characteristics. Depending on the extent of this issue across the cohort, the observed cardiovascular benefits reported in the study might actually be underestimated.

So where does that leave us? 

The sick-quitter effect (leading to underestimation of alcohol consumption and its risks) and inadequate control for probable healthy lifestyle changes (which might overestimate the health benefits of reduced drinking) present opposing potential influences on the direction of error in the size of the reported effect. But while we may not be sure about the exact magnitude of the true effect, to some extent, it doesn’t matter, as it’s extremely unlikely that the effect doesn’t exist at all.

The size of the observed effect is substantial and actually increased after accounting for confounding variables (crude HR: 0.83; 95% CI: 0.74-0.94 vs. adjusted HR: 0.77; 95% CI: 0.67-0.88), making it improbable that other unmeasured confounders could completely explain the reported outcomes. This implies that while the precise magnitude of the effect may be subject to debate – whether a bit smaller or larger than reported – the presence of a significant effect is virtually certain.

Moreover, the authors conducted separate sub-analyses stratified by various baseline demographic and health factors and found that the direction of the association persisted across subgroups, further strengthening the likelihood of a true effect. Though associations did not always achieve statistical significance for the various subgroups (likely due to inadequate statistical power among the smaller sub-cohorts), the overall trend toward reduced cardiovascular risk with reduced alcohol consumption was remarkably consistent between sexes, across physical activity levels, in smokers and non-smokers, for those both under and over age 65, and both normal-weight and overweight individuals, underscoring the broad applicability of these findings for diverse populations. Indeed, even considering subgroups of those who were already suffering from major health concerns at baseline (including hypertension, diabetes, dyslipidemia, heart failure, and atrial fibrillation), cutting alcohol was associated with comparable or even greater reductions in MACE risk than among subgroups without these conditions, indicating that making this particular step toward a healthier lifestyle can substantially improve health trajectories even later in life or after negative health conditions have already arisen.

A modest change with universal benefits

Kang et al. demonstrated that even modest reduction in alcohol consumption is associated with significantly lower the risk of cardiovascular events. For many individuals, the prospect of completely quitting alcohol might seem daunting or unattainable. However, Kang et al.’s findings offer a more achievable goal, as they show that substantial health benefits can be gained by cutting down to moderate drinking levels – and they show that the benefits apply to everyone

The cardiovascular benefits of reduced alcohol consumption were consistent across various subgroups for various demographic and health variables, dispelling the myth that certain individuals, based on their age or other health conditions, might be “too far gone” to benefit from reducing their alcohol intake. Whether you’re in your forties or your seventies, have overweight or average weight, the study indicates that the positive effects of reducing alcohol intake apply broadly.

Bottom line: it’s not too late!

Even with a history of heavy drinking, the answer to the question posed at the beginning of this newsletter is that, no, the damage is not already done; there is ample opportunity for improvement that translates into real risk reduction and the potential for a longer, healthier life. 

The study by Kang et al. highlights a critical but often overlooked aspect of cardiovascular health – the significant benefits of reducing heavy alcohol intake even after years of excessive consumption. Their work underscores that in this context, it is not too late to make positive changes for cardiovascular health and that efforts to do so would be far from futile, reaffirming the power of lifestyle change and personal choice – including the choice to seek support and help – in shaping one’s health trajectory. So, if you’re contemplating whether to cut back on alcohol, the message is clear: even modest reductions can significantly enhance heart health at any stage and for anyone. 

 

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References

1. Kang DO, Lee DI, Roh SY, et al. Reduced Alcohol Consumption and Major Adverse Cardiovascular Events Among Individuals With Previously High Alcohol Consumption. JAMA Netw Open. 2024;7(3):e244013-e244013. doi:10.1001/jamanetworkopen.2024.4013

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