A team of researchers in the United States and China have concluded that heavy alcohol consumption is a risk factor for stroke in Chinese men. But in doing so, they found that those who consumed light to moderate levels of alcohol were at a similar risk to nondrinkers, with some categories of drinkers demonstrating a possible health benefit.
The study has major implications for the Chinese health system and men of Asian descent in general, according to the authors of the study, which was published online Aug. 20 in the Annals of Neurology, because stroke is the leading cause of death and long-term disability in China. In previous research, "heavy alcohol consumption has consistently been identified as a risk factor for all types of stroke," wrote the study's authors. However, they noted that the effect of moderate drinking was, to this point, less certain.
The study, led by Lydia Bazzano of Tulane University School of Public Health and Tropical Medicine, included researchers from Johns Hopkins as well as the National Center for Cardiovascular Disease Control and Research in Beijing. In order to analyze the effect of drinking on stroke risk, the researchers pulled data on 64,338 Chinese men from 17 of 30 provinces in the country who participated in the 1991 China National Hypertension Survey.
At the beginning of that study, all of the men were over 40 years old and had not previously suffered a stroke. They provided information about their demographic characteristics, medical history and lifestyle risk factors, including alcohol consumption. The men were classified as nondrinkers, as consuming one to six drinks per week, seven to 20 drinks per week, 21 to 34 drinks per week, or 35 or more drinks per week.
Between 1999 and 2000, the researchers followed up with the study participants and recorded all incidents of stroke. By comparing the rates of stroke across the men's drinking habits, they determined that those drinking 21 drinks or more per week had a 22 percent greater risk of stroke than nondrinkers. Light drinkers, up to six drinks a week, showed a protective effect, with an 8 percent lower chance of stroke; moderate drinkers showed similar results to nondrinkers, who had no increased or decreased risk of stroke.
Alcohol consumption was shown to protect against ischemic stroke, which occurs when too little blood reaches the brain (usually due to clotting), and accounts for 80 percent of stroke cases in Western countries and 50 percent in Asian populations. For ischemic stroke, those who consumed between seven and 34 drinks per week showed a 12 to 13 percent lower risk than nondrinkers. Light drinkers showed a five percent lower risk and the heaviest of drinkers, at 35 drinks or more, had a risk factor similar to that of nondrinkers. But for hemorrhagic strokes, caused by a burst blood vessel (and often associated with hypertension), light drinkers showed a 24 percent lower risk than nondrinkers, whereas the heaviest drinkers were at a 23 percent greater risk. Men who drank seven to 20 and 21 to 34 drinks per week showed risks similar to nondrinkers.
The study's authors admitted that there are some limitations to their findings. "We were not able to assess the risk for stroke among binge drinkers," they wrote, adding that their conclusions could be the result of other unconsidered factors. The researchers, for instance, did record dietary information. However, they said that the "large sample size and high follow-up rate" of the research "provides excellent power for detecting an association."
"It is fair to assume that healthy, moderate drinkers don't need to change their habits to help avoid a stroke," Bazzano said. "Heavier drinkers should reduce their consumption to not more than three drinks per day." She added that people who consume large amounts of alcohol should consider changing their lifestyle to help avoid a stroke.
Bazzano also added that drinking wine responsibly may provide an additional protection against some types of stroke, based on the beverage's track record for helping circulation, but that this effect could not be measured in her study, since the men preferred liquor and beer.
The results of the study support other findings, such as a 1999 study that showed that moderate alcohol consumption can cut the risk of stroke in the elderly.