Feature Article: February 2019 – Alcohol and Health, Part One: Cardiovascular Health

This article uses as its foundation an editorial from the British Medical Journal entitled “Alcohol consumption and brain health.”¹ It possibly is a month or two too late given the past holidays and the increased imbibing associated with them, but nonetheless, here it is.

Observed first in research with myocardial infarction, epidemiological studies have often been cited for evidence of promoting better health in moderate drinkers compared to abstainers. When measures of health are plotted against consumption a “J-shaped curve” often appears. This has been seen in diabetes and stroke. Studies have also shown a “U-shaped” relationship between the amount of alcohol consumed and cardiovascular disease; it is also seen in the odds of reporting chronic widespread pain.² However, as more refined methods of investigating the relationship between alcohol and health are applied the magnitude of the apparent benefit is substantially reduced.

It is becoming apparent that the beneficial associations between low intensity alcohol consumption and all-cause mortality may, in part, be attributable to an inappropriate selection of the referent groups and weak adjustment for confounders.³ This article will look at the effects of alcohol consumption and cardiovascular disease.⁴ Next month we’ll consider dementia.

Several observational studies have shown that light to moderate drinkers have a reduced cardiovascular risk compared to non-drinkers. Optimal drinking levels were found to be about 6 to 12 drinks per week. More substantial drinking results in increased risk. This produces the “U-shaped” risk association seen with alcohol consumption. The biological explanation for the cardioprotective effect of alcohol is thought to be an increase in high density lipoprotein (HDL) cholesterol. However, findings for light to moderate drinkers could be due to unaccounted biases. Confounding factors could be poor health or lifestyle in non-drinkers or, similarly, lifestyles associated with light to moderate drinking.

An interesting approach was taken to address the possibility of a cardioprotective effect of light to moderate alcohol consumption. It used genetic variations and is known as Mendelian randomization. It avoids some of the key limitations of observational studies since allocation of genetic variants is random with regard to potential confounders and genotype is not modified by any characteristics of disease; the latter eliminating reverse causality. The genetic variations were in an alcohol metabolizing enzyme.

In alcohol metabolism, the alcohol dehydrogenase 1B gene (ADH1B) encodes the ADH1B enzyme. This enzyme catalyzes the oxidation of ethanol to acetaldehyde which is then broken down by acetaldehyde dehydrogenase. A single nucleotide polymorphism (rs1229984) in the alcohol dehydrogenase 1B gene causes a genetic variation in the enzyme that results in a more rapid conversion of alcohol to acetaldehyde, a metabolite of alcohol that causes unpleasant symptoms. This metabolite is associated with a flush response to alcohol consumption; it also causes significant nausea, headache, and light-headedness. As expected, affected individuals drink less, if at all, resulting in lower blood alcohol levels. There is also a lower risk of alcohol dependence among both adolescent and adults. This allele actually has a protective effect on the risk of alcoholism.

It was found that, as expected, individuals of European descent with this genetic predisposition consume less alcohol. Most importantly, they were also seen to have a reduced risk of coronary heart disease and ischaemic stroke, and lower levels of several established and emerging risk factors for cardiovascular disease. The comparison population were light to moderate drinkers without the genetic variant. This suggests that reductions of alcohol consumption, even for light to moderate drinkers, may be beneficial for cardiovascular health.

These results are not congruent with the findings of a cardioprotective effect that is associated with light to moderate alcohol consumption as reported by observational studies. This raises the possibility that the effects noted in those studies may have been due to residual confounding or selection bias. Overall, these findings suggest that reduction of alcohol consumption, even for light to moderate drinkers, is beneficial for cardiovascular health. The best alternative may possibly be an alcohol-free lifestyle. We’ll see how alcohol use is related to dementia next month.

References

1. Welch KA. Alcohol consumption and brain health. BMJ 2017; 357: 2645
2. Beasley MJ, Macfarlane TV, Macfarlane GJ. Is alcohol consumption related to likelihood of reporting chronic widespread pain in people with stable consumption? Results from UK biobank. Pain 2016; 16: 357-2552-2560.
3. Knott CS, Coombs N, Stamatakis E, et al. All cause mortality and the case for age specific alcohol consumption guidelines: pooled analysis of up to 10 population cohorts. BMJ 2015; 357h 384.
4. Holmes MV, Dale CE, Zuccolo L, et al. Association between alcohol and cardiovascular disease : Mendelian randomization analysis based on individual participant data. BMJ 2014; 349: g4164.

Mark H. Scheutzow, M.D., Ph.D., MHA, MPH, of Asheboro, NC, received his Doctorate of Medicine and of Philosophy from Ohio State University College of Medicine, Columbus, OH, and his Master of Health Administration/Master in Public Health from UNC Gillings School of Global Public Health, Chapel Hill, NC. Over the last five years he has completed over 1700 continuing medical education hours in pain, addiction, and psychiatric medicine, as well as training in Age Management Medicine. He is certified by, and a Diplomat of the American Board of Addiction Medicine, certified by, and a Diplomat of the American Academy of Pain Management, was a Founding Diplomat of the American Board of Holistic Medicine, and is a Fellow and Board Member of the American Association of Integrative Medicine. He practices Interventional and Chronic Pain Medicine, Addiction Medicine, Addiction Psychiatry and Regenerative Pain Medicine, in Winston-Salem and Greensboro, NC. Dr. Scheutzow can be reached at mscheutzow@msn.com.