Drinkers Beware: How Booze Can Make You Swoon
Jan. 31, 2000 (Atlanta) -- Mothers throughout the ages have warned that standing too quickly can cause lightheadedness. Researchers have known that alcohol can make matters worse. Now they know how. Alcohol, even in moderate amounts, impairs the ability of blood vessels to constrict upon standing, according to a report in the Feb. 1 issue of the Circulation, a journal of the American Heart Association. Doctors say older adults, diabetics, and those on medications that dilate blood vessels have an even greater risk for alcohol-related fainting.
To simulate gravitational stress upon standing, 14 young adults reclined in a metal cylinder as vacuum pressure was applied. Researchers measured blood flow at various levels of vacuum pressure. Data was collected for each subject on two separate days, once after consuming an alcohol-free drink and once after consuming the equivalent of two to three beers.
After the alcohol-free drink, blood vessels constricted normally and blood pressure did not change significantly. After the alcohol drink, 'blood vessels did not constrict normally and blood pressure was significantly reduced at every level of gravitational stress." At the lowest level, blood pressure dropped twice as much. It's the drop in blood pressure that causes fainting.
The authors say alcohol impairs the body's reflex feedback system. "Upon standing, gravity temporarily decreases the amount of blood returning to the heart. And this means there's less blood pumping to vital organs like the brain," says Virend Somers, MD, PhD, co-author and cardiologist at the Mayo Clinic. "But without the influence of alcohol, this response lasts only a moment because the body's reflex feedback system causes blood vessels to constrict and blood pressure rapidly increases." Doctors say some are at greater risk for alcohol-related fainting.
"Older adults, diabetics, and those on medications to dilate blood vessels frequently experience lightheadedness upon standing," says Krzysztof Narkiewicz, MD, PhD, lead author and associate professor of medicine at the Medical University of Gdansk, in Poland. "And these people are at even greater risk when drinking alcohol." Narkiewicz says alcohol-related fainting can lead to injury from falls.
"Older adults and diabetics often have this drop in blood pressure because their nervous systems don't respond as quickly," says Julian Aroesty, MD, the chief of clinical cardiology at Beth Israel Hospital and clinical associate professor of medicine at Harvard Medical School in Boston. "It's also very common in patients taking vasodilators [drugs that dilate blood vessels] like beta blockers, calcium channel blockers, angiotensin II blockers, ACE inhibitors, and nitroglycerine."
Aroesty tells WebMD that many falls can be prevented. "The body can metabolize [absorb] a glass of wine, a bottle of beer, or an ounce of strong spirits in about an hour. So those at high risk for alcohol-related fainting should probably limit themselves to a maximum of two drinks over two hours," says Aroesty. "And with or without alcohol, those at risk should be careful when getting out of bed. We recommend sitting for 15 seconds before standing and standing for 15 seconds before walking."