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Alcohol Intake and Stroke Risk: Can We Optimize Our Consumption?
Abstract & Commentary
By Alan Z. Segal, MD Associate Professor of Clinical Neurology, Weill Cornell Medical College, Attending Neurologist, NewYork-Presbyterian Hospital. Dr. Segal reports no financial relationships relevant to this field of study.
Synopsis: Heavy alcohol consumption increases the risk of both ischemic and hemorrhagic stroke.
Source: Bazzano LA et al. Alcohol consumption and risk for stroke among Chinese men. Ann Neurol 2007;62:569-578.
Large quantities of alcohol intake are thought to increase the risk of both hemorrhagic and ischemic stroke. Mild to moderate alcohol intake may prevent ischemic stroke. Red wine may offer a particularly unique benefit. Alcohol in any dose has not been shown to decrease the risk of cerebral hemorrhage. Geographic and ethnic differences may further exist. In an important addition to prior epidemiological studies, Bazzano et al correlate alcohol intake with stroke risk in a large cohort of Chinese men.
In this study, among 64,338 men studied over 493,351 person years of follow-up, there were 3434 strokes (825 [24%] hemorrhagic, 1724 [50%] ischemic, and 852 [25%] unknown). The relative risk (RR) of stroke was elevated for men drinking more than 21 drinks per week (RR = 1.22) compared to 1-6 or 7-20 drinks. A more pronounced increase (RR = 1.30) was found for stroke mortality among men in the highest intake category (more than 35 drinks per week). There was a suggestion from the data that moderate alcohol intake (<20 drinks per week) was protective for ischemic stroke and that heavy alcohol intake (>35 drinks per week) posed a particularly higher risk of hemorrhagic stroke, but none of these findings reached statistical significance. All of the study's findings were attenuated when a history of hypertension was factored into the multi-variate model, indicating the central role of this risk factor in both ischemic and hemorrhagic stroke.
The Chinese study is of interest, in part due to the increasing incidence of alcoholism in China as that country undergoes explosive economic development. Chinese men are disproportionately affected by this problem, as the authors observe, with a more than 30-fold increased frequency compared to women. Asian populations are of further interest due to an increased prevalence of hemorrhagic stroke compared to Western populations. Also, there are important inherited genetic polymorphisms among Asians, such as the alcohol intolerance conferred by allelic variations in the alcohol dehydrogenase enzyme. This may significantly affect alcohol intake patterns and may confound epidemiological studies due to other unknown genetic co-variants.
Should a "therapeutic window" for alcohol intake truly exist, it is a narrow one indeed. While light alcohol intake (1-2 drinks per day) may be protective, once daily consumption reaches three drinks, deleterious effects, in particular hemorrhagic stroke, may begin to accrue. Given that alcohol is an addictive substance, "heavy" use (5 drinks per day) always is a danger; it has well-known ill effects, not only in terms of stroke risk, but also on the brain and multiple other organ systems.