Cardiovascular disease remains the leading global cause of death. Controversy has surrounded the role that the consumption of alcohol plays in the risk for cardiovascular disease.
Previous studies have indicated that excess alcohol consumption increases the risk of cardiovascular disease, but low alcohol intake is regarded as beneficial to cardiovascular health. What is not clear from these studies is whether these health benefits are due to the low intake of alcohol, or whether these apparent benefits are due to other (healthy) lifestyle factors usually associated with people who drink very little alcohol.
An in-depth UK study, published in the journal JAMA Cardiology in 2022, shed new light on the risk of different levels of habitual alcohol intake on cardiovascular disease.
Previous studies:
The findings of past studies on the risks of different amounts of alcohol consumption on cardiovascular disease, were based on observational studies, which have consistently proposed cardiovascular benefits with light alcohol consumption.
In observational studies, researchers might study (observe) factors such as a characteristic or a behaviour, without attempting to change or influence the factors under observation.
On the other hand, in experimental studies, scientists intervene in the study to see what effect their manipulation has. In the case of trying to determine the effect of different amounts of alcohol consumption on the risk for cardiovascular disease, using controlled trials would be difficult to conduct due to all the variables associated with alcohol consumption. In addition, the effects of alcohol intake would take many years to show meaningful results, and such a study would be prohibitively expensive.
The 2022 UK study:
The pitfalls of observational research and experimental studies were overcome by a study method called Mendelian randomization, which is a technique using human genetic data. The study used gene variants that are linked to a given exposure – alcohol consumption in this case – as a proxy measure for that exposure. Using gene variants in the place of alcohol consumption eliminates variables due to other lifestyle or environmental factors.
To assess the relationship between alcohol intake and cardiovascular disease risk, the researchers used data from 371,436 individuals from the UK Biobank and the Mass General Brigham Biobank. Data from these individuals were followed over a ten-year period. They used nine gene variants that are associated with alcohol use disorder. Some of these genes directly impact the processing of alcohol, while other genes are associated with behavioural pathways that are implicated in alcohol addiction. The study also monitored a blood-based biomarker for alcohol use, as well as using information from self-reporting alcohol intake data.
The cardiovascular disease outcomes covered in the study included hypertension, coronary artery disease, stroke, heart failure, myocardial infarction (heart attack), atrial fibrillation (irregular heart rhythm), and coronary artery bypass graft surgery.
Alcohol intake levels were classified as light (less than 8 drinks/week), moderate (8-15 drinks/week), heavy (15-25 drinks/week), and abusive (more than 25 drinks/week).
Findings of the study:
In a nutshell, the study found that all amounts of alcohol consumption were associated with increased risk of cardiovascular disease. This refutes the findings of observational studies that low levels of alcohol intake were beneficial for cardiovascular health. Quite the opposite was found, with modest increases in risk with light alcohol consumption and exponentially greater risk increases with higher levels of alcohol intake. The study suggests that the reported cardioprotective effects of light to moderate alcohol consumption in observational studies may have resulted from healthier lifestyle factors.
The findings, supported by genetic evidence, showed significant effects on hypertension and coronary artery disease, while the risks associated with stroke, heart failure, and heart attack persisted, but were not statistically significant.
The other remarkable finding was that a linear increase in alcohol intake did not result in a linear increase in risk for hypertension and coronary artery disease, but that the risk increased exponentially. An increase of only one extra drink per day had the following effects:
- In the light drinking group, the risk for hypertension was raised by 30% and for coronary artery disease by 70%.
- In the moderate drinking group, the risk for hypertension was raised by 70% and for coronary artery disease by 80%.
- In the abusive drinking group, the risk for hypertension was raised by 160% and for coronary artery disease by 470%.
Thes findings suggest that the inverse is also true – risk decrease exponentially with progressively lower alcohol consumption. Reducing alcohol consumption with accompanying improvements to cardiovascular health may be significant for heavier drinkers and only slight for light drinkers.
Conclusion:
The findings are encouraging for anyone trying to cut back on alcohol intake, as it indicates that a meaningful reduction in the risk for cardiovascular disease does not require complete abstinence from alcohol, as even a small reduction in alcohol intake can have significant effects in lessening the risk of hypertension and coronary artery disease.
It is clear that no level of alcohol intake is good for cardiovascular health, however the risks are small at low levels of consumption, while the benefits of reducing alcohol intake can be substantial.
References:
Association of habitual alcohol intake with risk of cardiovascular disease. Published 25 March 2022. JAMA Network. (www.jamanetwork.com)
Reassessing the relationship between alcohol intake and cardiovascular disease risk. Published 2 December 2023. Dr Peter Attia. (www.peterattiamd.com)
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