Alcohol and Heart Disease

Measurements of Alcohol Consumption

Many beverages contain alcohol in varying amounts, necessitating standardization of the quantity of alcohol contained in various drinks. In general, the amount of absolute alcohol in grams is determined by the number of beverages consumed per day times the amount of alcohol in each beverage. In general, a 12-ounce bottle of beer, a 4-ounce glass of wine, and a 1 1/2-ounce shot of 80-proof spirits all contain the same amount of alcohol (one half ounce). Each of these is considered a “drink equivalent.”⁴ Recent studies have tried to determine whether specific beverages have unique protective or deleterious effects. The interpretation of this research is complex because one person often consumes several types of beverages.

Relation Between Alcohol Consumption and Total Mortality

A large number of observational studies have consistently demonstrated a J-shaped relation between alcohol consumption and total mortality.⁵ This relation appears to hold in men and women who are middle aged or older.^{6 7 8 9} The lowest mortality occurs in those who consume one or two drinks per day.¹⁰ In teetotalers or occasional drinkers, the rates are higher than in those consuming one or two drinks per day. In persons who consume three or more drinks per day, total mortality climbs rapidly with increasing numbers of drinks per day.

A number of studies have dissected the J-shaped curve into specific diseases. It is clear that a stepwise decline in CHD death occurs with increasing drinks per day. Because CHD accounts for one third or more of total deaths, those with no alcohol consumption have higher total mortality than those drinking one to two drinks per day.¹¹ On the other hand, mortality due to a large number of other diseases increases with an increasing number of drinks consumed per day. Diseases related to heavy consumption of alcohol and alcoholism include stroke,⁷ alcoholic cardiomyopathy,¹² several kinds of cancer, cirrhosis, and pancreatitis, as well as accidents, suicide, and homicide. It should be noted that heavy consumption of alcohol is a major cause of hypertension,¹³ so that the diseases related to hypertension, such as stroke, are generally related to alcohol consumption. Heavy consumption of alcohol also appears to affect heart muscle and possibly arterial tissues directly. Alcoholic cardiomyopathy is a common diagnosis in long-term alcoholics. While the relative and absolute risks of these diseases are negligible at one or two drinks per day, the mortality rates rise sharply.¹⁴ The J-shaped distribution for total mortality is then the sum of the protective effect on CHD mortality and the detrimental effect of high levels of consumption on these other causes of death.

Protective Effects of Alcohol Against CHD

More than a dozen prospective studies have demonstrated a consistent, strong, dose-response relation between increasing alcohol consumption and decreasing incidence of CHD. The data are similar in men and women in a number of different geographic and ethnic groups. Consumption of one or two drinks per day is associated with a reduction in risk of approximately 30% to 50%.¹⁵ Studies of coronary narrowings defined by cardiac catheterization or autopsy show a reduction in atherosclerosis in persons who consume moderate amounts of alcohol. In general, the inverse association is independent of potential confounders, such as diet and cigarette smoking. Concerns that the association could be an artifact due to cessation of alcohol consumption in persons who already have CHD have largely been disproved.¹⁶ No clinical trials have been performed to test the alcohol-CHD relation. However, the large numbers of observational studies support a true protective effect of moderate consumption of alcohol.

Mechanisms for Cardioprotective Effects of Moderate Consumption of Alcohol

Recent analyses suggest that approximately 50% of the protective effect of alcohol is mediated through increased levels of HDL cholesterol.¹⁷ HDL removes cholesterol from the arterial wall and transports it back to the liver and probably has several other protective effects on the arterial system. A number of epidemiological studies and small clinical trials have demonstrated that moderate consumption of alcohol raises HDL cholesterol levels.^{18 19 20} When HDL cholesterol was added to computer models predictive of CHD, about half the benefit of alcohol in protecting against CHD could be attributed to its effect on HDL levels.^{21 22}

A number of other mechanisms have been proposed to explain the other half of the protective effect of alcohol against CHD. One or two alcoholic drinks per day apparently do not affect other major risk factors, such as LDL cholesterol and blood pressure. Several studies have suggested that alcohol may affect blood clotting, either by causing the blood to clot less avidly through effects on coagulation factors and platelets or by enhancing the ability of the blood to break up clots when they form.^{23 24} These studies are supported by epidemiological data that suggest that acute alcohol consumption causes a short-term beneficial effect in protection against CHD in addition to long-term effects. Other studies have focused on the nonalcoholic components of alcoholic beverages, particularly in red wine and dark beer, which may have antioxidant properties.^{25 26 27} However, the epidemiological evidence favoring one type of beverage over another is inconsistent, possibly because of large differences in diet, smoking, and other risk behaviors among drinkers.²⁸ Again, at least half of the inverse association between alcohol and CHD appears to be directly linked to alcohol through increased HDL cholesterol levels.

Recommendations

It is unlikely that a randomized, controlled trial of alcohol consumption will ever be performed to establish a direct link between alcohol consumption and reduction in CHD and to define the risks and benefits of encouraging consumption of alcohol. In lieu of this scientific base, a number of scientific facts can be brought to bear on the development of recommendations about alcohol consumption.^{2 29 30 31 32} First, the beneficial effects of alcohol are limited to one or two drinks per day. Second, heavier consumption is related to a number of health problems. Third, it is clear that persons with medical and social conditions made worse by alcohol should not consume any alcohol whatsoever, including persons with prior diagnoses of hypertriglyceridemia, pancreatitis, liver disease, porphyria, uncontrolled hypertension, and congestive heart failure. Pregnant women and persons on certain medications that interact with alcohol should also refrain from consumption. Persons with a personal or strong family history of alcoholism are at risk for alcohol addiction and should avoid all alcoholic beverages.

These facts preclude widespread public health recommendations to either encourage or prohibit alcohol consumption. In the United States 100 000 excess deaths can be attributed to alcohol-related diseases each year.¹¹ On the other hand, if current consumers of alcohol all abstained from drinking, approximately 80 000 excess deaths would occur.² Most of the excess deaths due to alcohol occur in people younger than 45 years, whereas deaths reduced by alcohol are generally in age groups with high CHD rates, ie, 45 years or older. In either case, general public health education messages about alcohol may be difficult to develop, so that they target only persons for whom moderate consumption of alcohol would have a positive cost-benefit ratio.

Therefore, the following recommendations may be made for the individual patient who is considering beginning or continuing to drink alcohol.

1. Consult a physician for an assessment of the benefits and risks of alcohol consumption. Persons with a personal or family history of alcoholism, hypertriglyceridemia, pancreatitis, liver disease, certain blood disorders, heart failure, and uncontrolled hypertension, as well as pregnant women and persons on certain medications that interact with alcohol, should not consume any alcohol. Any recommendations should be tailored to the individual patient's risks and potential benefits.

2. If no contraindications to alcohol consumption are present, moderate consumption of alcohol (one or two drinks per day) may be considered safe.

3. Alcohol should never be consumed when operating machinery or motor vehicles.

4. The risks and benefits of alcohol consumption should be reviewed periodically as part of regular medical care. In the event of excess consumption, problem drinking, or deleterious consequences of drinking, recommendations for alcohol consumption should be revised.

5. Adolescents and young adults should be targeted for assessment and advice before potentially deleterious habits of consumption become established.