Diseases of the heart and blood vessels (i.e., cardiovascular diseases [CVDs]) are a major cause of illness and disability in the United States. Heart disease is the leading cause and stroke is the third leading cause of death among adult Americans. Together, these two conditions account for more than 40 percent of all deaths annually (Dufour 1996).
Researchers have studied extensively the role of alcohol in CVD, especially in relation to drinking level. Heavier drinking (see the following section, "Definitions of Moderate Drinking") is related to higher risk of heart muscle disorders (i.e., cardiomyopathy), high blood pressure (i.e., hypertension), brain damage from ruptured blood vessels (i.e., hemorrhagic stroke), and heart rhythm irregularities (i.e., arrhythmias). Lighter drinking is related to lower risk of coronary artery disease (CAD) and of ischemic stroke, which is characterized by blockage of blood vessels that supply the brain.(1)
Sweeping generalizations circulated in the popular media have perpetuated public misconceptions about the effects of moderate drinking on CVD. In truth, the relationships between drinking and CVD are both complex and interconnected (Klatsky 1995a). Discussions of alcohol's effects on CVD must clearly differentiate between different levels of drinking as well as the specific type of CVD being considered.
This article briefly reviews the effects of heavier drinking on certain CVDs and considers at greater length the cardiovascular effects of moderate drinking. The article concentrates on CAD for two major reasons. First, CAD is the most common type of CVD and therefore dominates epidemiological statistics when CVDs are studied as a group. Second, alcohol has been reputed to have a protective effect against CAD. The discussion of CAD suggests possible mechanisms to account for this protective effect, including the potential role of beverage type. Finally, the article discusses implications of the alcohol-CVD relationship in terms of total mortality and overall public health.
DEFINITIONS OF MODERATE DRINKING
Definitions of moderate drinking vary widely (see the article by Dufour, pp. 5-14). This article defines moderate drinking as the consumption of fewer than three standard drinks per day. A standard drink is equivalent to approximately 12 ounces (oz) of beer, 5 oz of wine, or 1.5 oz of distilled spirits, each of which contains approximately 12 grams (0.5 oz) of alcohol.
Problems inherent to epidemiological studies of alcohol and CVD include individual susceptibility and the categorization of drinking levels. Individual factors that influence interpretation of study results include sex, age, dietary habits, cigarette smoking, the consumption of caffeinated beverages, and various psychosocial factors that are difficult to characterize and measure.
The characterization of drinking levels is complicated by the use of subjects' self-reported estimates. In particular, heavier drinkers may underestimate their alcohol consumption. If some proportion of heavy drinkers report lighter drinking, then the "lighter" drinking group will include some people who really drink more, and a condition related only to heavy drinking (e.g., alcoholic cardiomyopathy) may erroneously appear to be related to moderate alcohol consumption (Klatsky 1994).
Another potential source of error is failure to consider individual differences in drinking patterns. Subjects in population studies are generally requested to describe their average total alcohol consumption over a given time period (e.g., 1 week or 1 month). Thus, a person who habitually consumes 2 drinks each evening might report the same average weekly consumption as a person who hypothetically consumes 14 drinks within a few hours every Saturday night. The health risks posed by such widely varying patterns of consumption may differ substantially.
EFFECTS OF HEAVY DRINKING
Clinicians and researchers have long recognized that alcohol consumption can directly damage heart muscle cells independently of any other cardiovascular effect (Klatsky 1995a). …