RECENTLY, news of a large new study looking at the effect of alcohol on the risk of cardiac disease was published in the Journal of the American Medical Association. For many physicians, this study has changed how we think about moderate drinking and the risk of cardiac disease.

Alcohol is used in many social situations and while heavy drinking has clearly been associated with a variety of poor health outcomes. Infrequent or moderate drinking has been associated with a reduced risk of coronary artery disease and coronary disease mortality. A major challenge has been the quality of the evidence that supports this conclusion as most of the data has been obtained from observational trials. While data of this type is useful, it leaves open the possibility that the results suggesting the beneficial effect of alcohol may be related to other factors, such as lifestyle, traditional cardiac risk factors, health status, socio-economic factors, etc. For example, people who drink infrequently may exercise more frequently, have diets with less saturated fats, or may have lower weight than non-drinkers. In that scenario the positive health effects are not related to use of alcohol but the associated healthy behaviours. Normally these issues can be sorted out using a randomised control trial in which the patients are selected at random and should be alike in every respect aside from the use of alcohol, but this kind of study is exceedingly difficult to do for lifestyle changes that need to be followed over years in a large number of patients.

Alcohol and health

Alcohol, although used widely in our society, is associated with many diseases, poor health, and poor socio-economic outcomes. It is estimated that in the United States of America, alcohol is the third-leading cause of preventable death causing approximately 5,000 deaths per year. Much of this is seen in patients who drink heavily. (In the United States heavy drinking is considered more that two drinks per day for men and more than one drink per day for women). Excessive alcohol intake is linked to liver disease, cirrhosis and its complications, including liver cancer. Heavy alcohol use can damage the muscle of the heart, leading to cardiac enlargement and weakness of the cardiac muscle causing heart failure. The pancreas can be affected, leading to chronic pain and malabsorption of food. Irritation of the stomach and oesophagus can lead to chronic pain or bleeding from the gastrointestinal tract. Alcohol use is associated with an increased incidence of hypertension, diseases of the brain, and peripheral nerves, increases in the risk of infectious disease and increases in the risk of many cancers, including the malignancies of the head and neck, gastrointestinal system, and breast. Its use has been associated with various psychiatric conditions, including an increased risk of suicide. Aside from its direct effects on health, one must consider the role of alcohol in motor vehicle accidents, trauma, and poor socio-economic outcomes, such as homelessness and the effects on the family.

Alcohol and the risk of heart disease

In contrast to the litany of poor outcomes listed above, it has long been believed that the moderate use of alcohol has a protective effect on the risk of heart disease (particularly of the coronary arteries). This can be demonstrated by the so-called French paradox. In France it was noted that, despite high rates of smoking and diets with elevated levels of saturated fats, the population of France had lower-than-expected levels of heart disease. It was postulated that this reduction in risk was related to the high level of alcohol use, particularly red wine. Observational studies over that past 40-50 years have noted the association between moderate drinking and lower cardiac risk. Initially, it was thought that this was a property of red wine as red wine contains several chemicals which have been demonstrated to have anti-inflammatory and antioxidant properties. However, other studies have found protective effects from drinking other forms of alcohol, including beer, spirits, and white wine/champaign.

Mechanisms for the reduction in heart disease with moderate alcohol consumption have included changes in cholesterol profile, reduction of inflammation in the arterial wall, the antioxidant effects of alcohol, and improvements in the clot destroying systems in the body. There has been great debate as to the amount of alcohol that is required to produce these effects. It is unclear when alcohol ceases to be a net positive benefit, particularly in women, those above the age of 50, and in people who have established cardiac disease, including hypertension, congestive heart failure, secondary to weak heart muscle, and atrial fibrillation. For example, some studies have suggested that a safe level of alcohol intake for women is one drink per week as opposed to one drink per day.

What is new?

In March, the Journal of the Medical Association reported on the work of Biddinger et al. They describe their experience with the United Kingdom Biobank data. The study included approximately 370,000 people and is one of the largest studies on habitual drinking and its effects on cardiac disease. What makes their work unique is the use of genetic data to identify markers for alcohol consumption and to associate this with cardiac outcome. Since the genetic markers are randomly obtained at conception, they were able to isolate the effects of alcohol from other confounding factors. They were also able to stratify the risk of drinking alcohol according to the amount of alcohol that each person consumed. This study had several important findings. The first was that light and moderate drinking was associated with healthy behaviour, including lower rates of smoking, lower weight, higher levels of physical activity, higher vegetable intake, and better self-reported health. Once these factors were considered the beneficial effects of alcohol were significantly attenuated, suggesting that in people who drink small to moderate amounts of alcohol their healthy behaviour is what drives the reduction in risk as opposed to the use of alcohol

The second important finding was the association between increasing amounts of alcohol and higher rates of heart disease (particularly coronary disease and hypertension). It is important to note that, at any level of alcohol use, there was increased risk of heart disease, although this increase was relatively small in light drinkers. The third important finding was that the increase in risk of heart disease with increasing alcohol intake is non-linear. That is, a small increase in alcohol intake is associated with large increase in cardiac risk. In this study, any use of alcohol was associated with an increased risk of hypertension, coronary artery disease, myocardial infarction, stroke, heart failure, and atrial fibrillation.

What do we tell our patients?

The key point of this study is that we should not be drinking alcohol to lower cardiac risk. If patients are interested in improving cardiac outcomes, they should be trying to follow the lifestyle measures and risk- reduction strategies that we have frequently discussed in prior articles. For patients who do drink alcohol, they should note that alcohol use is associated with an increased risk of several cardiac conditions. They can, however, take comfort in the fact that infrequent or light drinking is associated with a relatively minor increase in risk. Patients who are at higher risk of heart disease or who have established heart disease should think carefully about drinking and minimise this as far as possible. ideally, they should avoid alcohol. Lastly, heavy alcohol use should be avoided, not only for cardiac reasons, but also for the multitude of toxic effects that alcohol has on the body.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Correspondence to info@caribbeanheart.com or call 876-906-2107