Moderate Drinkers' Lower CHF Risk Not MI-Related

BOSTON, July 14 -- Protection against congestive heart failure by moderate drinking appears to be conferred by a previously unsuspected mechanism, according to researchers here.

Compared with lifetime abstainers, those who drank an average of about two drinks per day were 35% less likely to suffer congestive heart failure, said Kenneth J. Mukamal, M.D., M.P.H., of the Beth Israel Deaconess Medical Center.

However, the difference was not the result of moderate drinkers having fewer non-fatal myocardial infarctions, as one might have suspected, Dr. Mukamal and colleagues reported in the July 18 issue of the Journal of the American College of Cardiology.

"Because MI is an extremely common risk factor for congestive heart failure, and moderate alcohol consumption is associated with reductions in MI and MI-associated mortality, reductions in risk of MI during follow-up might have been expected to explain the lower rates of congestive heart failure observed among moderate drinkers," Dr. Mukamal and colleagues said.

But the results held true even after adjusting for non-fatal MI and other risk factors for congestive heart failure. "This implies that some other mechanism may be responsible for the association between moderate alcohol consumption and lower risk of incident congestive heart failure," they said.

Possible mechanisms include alcohol's known ability to lower pulmonary artery wedge pressure, cause arterial vasodilation, and improve endothelial function, the investigators said.

The study analyzed data on about 5,600 Medicare enrollees participating in the Cardiovascular Health Study. Healthy participants were recruited in the late 1980s and early 1990s and followed for up to 10 years. Participants' average age was 72, and roughly half were women.

Compared with lifetime abstainers, those who drank one to six drinks per week were at lower risk for congestive heart failure (hazard ratio=0.82; 95% CI=0.67 to 1.00; P=.05).

For those who drank seven to 13 drinks per week, the risk was even lower (HR=0.65; 95% CI=0.47 to 0.91; P=.01).

However, the protective effect vanished for those who drank 14 or more drinks per week (HR=0.87; 95% CI=0.67 to 1.14; P=.32).

Former drinkers were at increased risk compared with lifetime abstainers (HR=1.51; 95% CI=1.23 to 1.85; P<.001), the study found. Although the investigators did not speculate as to why, other scientists have suggested that many former drinkers may have stopped consuming alcohol because of poor health.

"Moderate alcohol use is associated with a lower risk of incident congestive heart failure among older adults, even after accounting for incident MI and other factors," the investigators concluded.

However, one should not start drinking in hopes of lowering congestive heart failure risk on the basis of this study, Dr. Mukamal cautioned. The observational study can not prove a causal link or identify the biological mechanisms that may underlie any protective effect "As in any observational study, confounding by factors unmeasured or poorly measured in our study, such as dietary habits, could contribute to biased estimate," he said.

Other limitations pointed out by the authors included the type of population studied and the small number oeavy drinkers in the study. They wrote that "participants were generally healthy, community-dwelling older adults. As a result, our results cannot be extrapolated to other populations without an appropriate degree of caution. Relatively few of the Cardiovascular Health Study participants were heavy drinkers, and the range of alcohol intake was truncated even among the heaviest drinkers. As a result, our ability to define the potentially hazardous effects of truly heavy alcohol consumption was limited."