August 14, 2001
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"There's considerable evidence that alcohol causes hypertension," said Paul Whelton. "The French army used to give their troops a free ration of brandy in the 1800s. They noticed that after the soldiers got the brandy, their blood pressure was sky high."
Although the relationship between alcohol and blood pressure was noticed as early as the 19th century, it has been infrequently examined in long-term studies. Whelton, senior vice president for health sciences, was a co-investigator in a large study of the relationship between hypertension and alcohol that was published in the journal Hypertension.
Supported by the National Heart, Lung and Blood Institute, the study looked at more than 8,000 people between the ages of 45 and 64 who were free of hypertension and coronary heart disease at the beginning of the study. The subjects were followed for six years.
"What's interesting about this study is that it's a large study," Whelton said. "It's geographically diverse and includes a substantial number of both black and white men and women."
Participants were selected from four sites in the United States--Forsyth County, N.C.; Jackson, Miss.; suburban Minneapolis; and Washington County, Maryland. All of the subjects in Jackson were African American, while blacks made up only a small part of the other groups. The study was restricted to those who described themselves as either black or white.
The study depended on participants to tell researchers about their drinking habits. It's possible that they may have underreported or underestimated how much alcohol they consumed, which would mean that the threshold at which blood pressure starts to increase is a bit higher than the study indicates. But the basic association between drinking and blood pressure would not be affected by underreporting of alcohol consumption.
"Alcohol is a pretty interesting risk factor for cardiovascular disease," Whelton said. "It has both negative consequences and positive consequences."
Low to moderate levels of alcohol consumption seem to improve an individual's blood cholesterol. So, for many people, especially those with a lower level of blood pressure, moderate consumption of alcohol is acceptable and possibly beneficial. But alcohol has only one effect on blood pressure and that's to make it go up. Exactly how alcohol creates this effect is still unclear.
Researchers found that those who drank more than 210 grams of ethanol, or the equivalent of about three drinks a day, had an increased risk of hypertension. The type of beverage consumed did not seem to make a difference. They estimate that about one in five cases of hypertension in those consuming three or more drinks per day could be attributed to alcohol consumption.
For African-American men who participated in the study, low to moderate amounts of alcohol was associated with increased blood pressure. One other study has had the same results. Further research needs to be done before these results can be considered conclusive, but it may be that low levels of alcohol carry a greater risk of hypertension for African Americans.
"We don't know for sure whether there's a true difference between blacks and whites in their susceptibility to the blood pressure effects of alcohol," Whelton said. "However, there is no doubt that the blood-pressure elevation caused by alcohol is entirely reversible. When you stop drinking, blood pressure goes down."
"For those who are taking on average three or more drinks a day, alcohol increases their risk substantially," Whelton said. "If they were to stop drinking alcohol, they'd have about a 20 percent lower prevalence of hypertension. We think alcohol is quite an important reversible risk factor for hypertension."
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