Alcohol intake and the risk of stroke.

Alcohol consumption has been reported to have both beneficial and harmful effects on the incidence of stroke. Different drinking habits may explain the diversity of the observations, but this is still unclear. We reviewed recent clinical and epidemiological studies to find out whether alcohol intake could increase or decrease the risk for stroke. By a systematic survey of literature published from 1989 to 1997, we identified 14 case-control studies addressing alcohol as a risk factor for haemorrhagic and ischaemic stroke morbidity and fulfilling the following criteria: the type of stroke was determined by a head computerised tomography scan on admission or at autopsy; and alcohol consumption was verified using structured questionnaires or by personal interviews. In some studies, adjustment for hypertension abolished the independent role of alcohol as a risk factor. On the other hand, the studies covering even recent alcohol intake showed in many cases that heavy drinking is an independent risk factor for most stroke subtypes, and that the risk may decrease relatively rapidly after the cessation of alcohol abuse. In some studies, regular light to moderate drinking seemed to be associated with a decreased risk for ischaemic stroke of atherothrombotic origin. In conclusion, recent heavy alcohol intake seems to be an independent risk factor for all major subtypes of stroke. The ultimate mechanisms leading to the increased risk are unclear. The significance of alcohol as a risk factor has been demonstrated in young subjects because they are more often heavy drinkers than the elderly. Several factors to explain the beneficial effect of light to moderate drinking have been proposed.