Harvard: Light alcohol intake increases cardiac risks

A new study using Mendelian Randomization (MR) challenges previous recommendations that light alcohol consumption is good for the heart. The peer-reviewed study was published in the March 25 edition of the Journal of the American Medical Association. 

Mendelian Randomization is a relatively new research tool that uses genes to establish cause and effect. Knowing what causes any condition like coronary heart disease is complicated due to many associations that can confound research.

For example, between alcohol intake and heart disease, is it the alcohol or cigarette smoking since many drinkers also smoke. Is it the weight, physical activity, vegetable intake, red meat consumption, the C-Reactive Protein, or high total cholesterol that caused the heart disease?

In this Harvard study, the authors looked at the people with the genes associated with alcohol drinking, their amount of alcohol intake, and cardiac disease outcomes.

The research used data from the UK Biobank. The UK Biobank stores medical information among volunteers, including their genetic sequences, imaging studies, and blood work.

Regular readers of this website have read about the UK Biobank in the article, A drink a day shrinks the brain, which showed that chronic light alcohol drinking decreases the gray and white matter of the brain.

In the study, Association of Habitual Alcohol Intake With Risk of Cardiovascular Disease included 371 463 study participants with the following characteristics:

• The average age was 57.0 (+/- 7.9) years
• 172 400 (46%) were men,
• The mean alcohol consumption was 9.2 (+/- 10.6) standard drinks per week
• One hundred twenty-one thousand seven hundred eight participants (33%) had hypertension, and 27 667 participants (7.5%) had CAD.

The drinking groups were classified as

1. Abstainers (0 drinks/week)
2. Light (>0-8.4 drinks/week)
3. Moderate (>8.4-15.4 drinks/week)
4. Heavy (>15.4-24.5 drinks/week)
5. Abusive (>24.5 drinks/week)

Results

Alcohol increases cardiovascular risk factors like systolic and diastolic blood pressure, C-reactive protein, apolipoprotein B, and LDL cholesterol levels.

In both light and moderate drinkers, a 1–drink per day increase was associated with a significantly increased odds of hypertension (light drinkers: odds ratio (OR), 1.3; moderate drinkers: (OR, 1.7) and coronary artery disease (light drinkers: OR, 1.7, moderate drinkers: OR, 1.8.

An odds ratio of 1.8 means that moderate drinking increases the odds of having hypertension by 80%.

A 1–drink per day increase in abusive drinkers was associated with even greater risks of hypertension (OR, 2.6) and Coronary artery disease. (OR, 5.7).  

Similar trends were noted for other cardiovascular diseases and
all-cause mortality. The graphs below show that higher alcohol consumption increases the incidence of cardiovascular diseases like hypertension, myocardial infarction, heart failure, stroke, and atrial fibrillation.

The two graphs below show that the number of alcoholic drinks per week positively correlates with total mortality from all causes. The figure on the right side is notable for a sudden increase in total mortality among those who have more than 21 drinks a week.

If alcohol is terrible for the heart, Why was it recommended before in the Dietary Guidelines for Americans 2020-2025 by the US Department of Agriculture? In its recommendation, the USDA said,

Limiting alcoholic beverages (if consumed) to 2 drinks or less a day for men and 1 drink or less a day for women.

USDA

The authors mentioned that based on previous studies,[3],[4], moderate drinkers have healthier lifestyle behaviors, self-report better overall health, have lower rates of smoking, lower Body Mass Index, higher physical activity, and higher vegetable intake compared to abstainers.

Mass Gen Brigham Biobank

To show consistency and follow the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline, the analyses were done using 30 716 individuals from the Mass General Brigham Biobank.

The results are the same. That is, alcohol intake showed directionally consistent associations with the systolic and diastolic blood pressures.

Take away message

Light alcohol intake is associated with modest increases in cardiovascular risk. In contrast, heavier consumption was related to exponential clinical and subclinical cardiovascular disease risk increases.

 

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References:

1. Biddinger KJ, Emdin CA, Haas ME, et al. Association of Habitual Alcohol Intake With Risk of Cardiovascular Disease. JAMA Netw Open. 2022;5(3):e223849. doi:10.1001/jamanetworkopen.2022.3849.
2. Kranzler HR, et al. Genome-wide association study of alcohol consumption and use disorder in 274,424 individuals from multiple populations. Nat Commun. 2019 April 2;10(1):1499. doi: 10.1038/s41467-019-09480-8. Erratum in: Nat Commun. 2019 May 17;10(1):2275. Erratum in: Nat Commun. 2019 September 3;10(1):4050. PMID: 30940813; PMCID: PMC6445072.
3. Naimi  TS, Brown  DW, Brewer  RD,  et al.  Cardiovascular risk factors and confounders among nondrinking and moderate-drinking US adults.   Am J Prev Med. 2005;28(4):369-373. doi:10.1016/j.amepre.2005.01.011 PubMed Google Scholar Crossref
4. Hansel  B, Thomas  F, Pannier  B,  et al.  Relationship between alcohol intake, health, and social status and cardiovascular risk factors in the Urban Paris-Ile-de-France Cohort: is the cardioprotective action of alcohol a myth?   Eur J Clin Nutr. 2010;64(6):561-568. doi:10.1038/ejcn.2010.61 PubMed Google Scholar Crossref

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