Data from epidemiologic studies are quite consistent for the relation of alcohol consumption with the different types of stroke: for ischemic stroke, an inverse association with moderate drinking and a possible increase with heavy drinking (a “j-shaped curve”); for hemorrhagic stroke, a direct positive association, although some studies suggest that there may be a threshold level for an increase in risk. Data are mixed on a possible association between the most uncommon type of stroke, subarachnoid hemorrhage (SAH). The present paper presents results of a meta-analysis relating reported intake of alcohol with subsequent risk of SAH. It was based on 14 observational studies reporting data on 483,553 individuals and 2,556 patients.
Forum members agree that this study suggests that alcohol intake, especially heavier drinking, increases the risk of SAH, although there was considerable heterogeneity among studies from different parts of the world, there were no countries from the Mediterranean area included, and there was no accounting for pattern of drinking (binge versus moderate regular) or type of beverage, all of which may affect risk.
The authors concluded that there was no relation between light (<15 g/day) or moderate alcohol consumption (15-30 g/day) compared with abstaining individuals; this was based on statistically insignificant increases in RR of 1.27 (95% CI: 0.95, 1.68) and 1.33 (95% CI: 0.84, 2.09) for these two groups, respectively. However, Forum members suggest that there could be a slight increase in risk even for these two groups. For heavier drinkers (> 30 g/day, about 2 ½ to 3 typical drinks per day), the data indicate an increase in risk: RR=1.78 (95% CI: 1.46, 2.17).
It should be noted that the overall risk of total stroke is decreased from moderate drinking, as the most common type of stroke is ischemic, and moderate drinking has consistently been shown to lower such risk; this is especially related to lowering the risk of atherosclerotic or embolic clots. However, while rare, SAH is often a devastating disease, and the risk may be increased from alcohol consumption through its effects on decreasing coagulation.
Reference: Yao X, Zhang K, Bian J, Chen G. Alcohol consumption and risk of subarachnoid hemorrhage: A meta-analysis of 14 observational studies. Biomedical Reports 2016;5:428-436.