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New perspectives on the role of alcohol in heart disease
An interesting study by U. Schminke et al has thrown doubt over alcohol’s role in preventing ‘hardening of the arteries’ or atherosclerosis. The study suggests that most of the potentially protective effects of alcohol on the risk of a heart attack may not be through reducing ‘thickening’ of the arteries, but may relate more to alcohol’s effects on blood clotting, on the functioning of the lining of the arteries (endothelial function), and rupture of plaques.

The research looked at alcohol intake and cartoid intima-media thickness (IMT) in 1,230 men and 1,190 women. At between 61 to 80g alcohol intake a significant inverse association between IMT and alcohol intake was found, but at > 80g/d in men the J-shaped curve became insignificant after controlling for HDL cholesterol and fibrinogen. In women, neither a J-shaped relation nor significant differences in IMT between the drinking and non-drinking groups were found.

The authors conclude that alcohol consumption is inversely correlated with carotid IMT in men but not in women but that the daily level of alcohol intake that shows a maximum protective effect against atherosclerosis is above sensible drinking guidelines. For light drinking (e.g., 1/2 to 2 drinks/per day), a level that has been associated with large decreases in the risk of heart attacks, show little effect on IMT.

A second study by RC Ellison et al evaluates the relation of alcohol intake to the presence of Calcified atherosclerotic plaque in the coronary arteries (CAC) and calcified plaque in the aorta among 3,166 white and African-American subjects from the NHLBI Family Heart Study who Several studies this quarter have thrown new perspectives on the role of alcohol in heart disease.

underwent cardiac CT scans. The authors conclude that despite its frequently demonstrated beneficial effects on coronary artery disease risk, alcohol consumption in this study was not associated with calcified atherosclerotic plaque in the coronary arteries or in the aorta. This suggests that its effects on cardiovascular risk may occur through mechanisms other than those associated with the development of calcified plaque.

Curt Ellison comments on the research ‘Based on this and most previous papers on this topic, we suggest that studies of the effects of alcohol on cardiovascular risk cannot use IMT or CAC as indices of effect, but should rely on the effects of alcohol intake on clinical events (myocardial infarction, stroke, etc.).

Further, we interpret this and many previous studies as emphasizing that the effects of alcohol intake on coagulation, fibrinolysis and endothelial function may be more important than alcohol’s effects on atherosclerosis in explaining the usual finding of lower rates of myocardial infarction and cardiovascular death among moderate drinkers.

A third study by KJ Mukamal et al looked at the alcohol consumption of 16,415 individuals in the Copenhagen City Heart Study to study and identify cases of atrial fibrillation (AF) by routine study ECGs and hospitalizations. AF is a common disorder of heart rhythm, and markedly increases the risk of stroke.

1071 cases of AF occurred. Among both women and men, moderate alcohol consumption was not associated with AF. However, consumption of 35 or more drinks per week among men resulted in a 45% increase in risk ; few women consumed this amount of alcohol. Approximately 5% of cases of atrial fibrillation among men were attributable to heavy alcohol use. The authors conclude that heavy alcohol consumption is associated with a higher risk of atrial fibrillation, at least among men. This relationship does not appear to be related to the adverse effects of heavy drinking on coronary heart disease or blood pressure. It has long been known that binge drinking acutely increases the risk of AF.

Information on binge drinking was not available in this study, so we cannot know if repeated binge drinking, rather than a constant high intake of alcohol, was the major cause of increased risk of AF among the heavier drinking subjects.

Sources: Schminke U et al Association between alcohol consumption and subclinical carotid atherosclerosis. The Study of Health in Pomerania. Stroke. 2005;36:1746-1752.

Ellison RC et al Is alcohol consumption associated with calcified atherosclerotic plaque in the coronary arteries and aorta? Am Heart J 2005

Mukamal KJ, et al consumption and risk of atrial fibrillation in men and women. The Copenhagen City Heart Study. Circulation 2005;112:1736-1742.

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