Moderate alcohol intake does not appear to protect against stroke in men, according to a large prospective study in China. The findings in the Lancet contrast with previous reports suggesting a potential protective effect.
Roughly 500,000 Chinese adults reported on their alcohol intake at baseline. Of these, some 160,000 underwent genotyping for variants that cause a flushing reaction after drinking. Researchers then conducted two separate analyses: a traditional epidemiologic analysis, and a genetic epidemiologic analysis in which participants who tested positive for those variants were presumed to drink little or no alcohol and thus served as a “control” group.
Participants were followed for stroke incidence over some 10 years. In the traditional epidemiologic analysis, men who reported moderate drinking (about 1–2 drinks per day) at baseline had lower risk for stroke than nondrinkers and former drinkers. However, in the genetic epidemiologic analysis, moderate drinking was no longer protective against any type of stroke. (In women, alcohol intake was low regardless of genetic variants.)
The authors write, “The genetic findings imply that, among all men, alcohol was responsible for about 8% of ischemic strokes and 16% of intracerebral hemorrhages.” They note that the genetic analysis helps limit confounding by other health factors, which is often seen in traditional analyses using self-reported alcohol intake.
Dr. Seemant Chaturvedi of NEJM Journal Watch Neurology commented: “The incorporation of a genetic component to the analysis is interesting. However, the study was done entirely in China, and it is well known that East Asian individuals metabolize alcohol differently. So whether these results apply to Western populations is unclear. Until new studies are done, it is sensible to follow the AHA recommendations on mild to moderate alcohol consumption.”
Overall, genetic epidemiology shows that the apparently protective effects of moderate alcohol intake against stroke are largely non-causal. Alcohol consumption uniformly increases blood pressure and stroke risk, and appears in this one study to have little net effect on the risk of myocardial infarction.
Read the full article here.
SOURCE: NEJM Journal Watch & Lancet
