Alcohol use and retinal vessels: insights into the mechanism of alcohol-induced stroke

Alcohol use is a recognized risk factor for stroke. We hypothesized that alcohol use may increase the risk of stroke, independent of an effect on blood pressure, by causing cerebral vasoconstriction. To examine this, we used retinal vessels as a marker for cerebral vessels and analysed the cross-sectional associations between alcohol use and total retinal vessel width in 741 Japanese and 434 American white male telephone executives. Systolic and diastolic blood pressures were negatively associated with retinal vessel width in the Japanese (p less than 0.0001, 0.0001, respectively) but this association did not achieve statistical significance in the Americans (p less than 0.1, 0.3). Japanese drinkers had a larger mean retinal vessel width than Japanese abstainers, while American drinkers had a smaller retinal vessel width than abstainers. These associations between alcohol use and retinal vessel width were not significant within nationalities but the interaction between alcohol use and nationality was significant, independent of other stroke risk factors (p less than 0.04). Although these results do not support the initial hypothesis, they are consistent with known biological differences in alcohol metabolism between Japanese and American men and support different effects of alcohol use on retinal vessel calibre in these two nationalities.