BACKGROUND: Observational studies have suggested a complex relationship between alcohol consumption and stroke, dependent on sex, type of stroke and outcome (morbidity vs. mortality). We undertook a systematic review and a meta-analysis of studies assessing the association between levels of average alcohol consumption and relative risks of ischemic and hemorrhagic strokes separately by sex and outcome. This meta-analysis is the first to explicitly separate morbidity and mortality of alcohol-attributable stroke and thus has implications for public health and prevention. METHODS: Using Medical Subject Headings (alcohol drinking, ethanol, cerebrovascular accident, cerebrovascular disorders, and intracranial embolism and thrombosis and the key word stroke), a literature search of MEDLINE, EMBASE, CINAHL, CABS, WHOlist, SIGLE, ETOH, and Web of Science databases between 1980 to June 2009 was performed followed by manual searches of bibliographies of key retrieved articles. From twenty-six observational studies (cohort or case-control) with ischemic or hemorrhagic strokes the relative risk or odds ratios or hazard ratios of stroke associated with alcohol consumption were reported; alcohol consumption was quantified; and life time abstention (manually estimated where data for current abstainers were given) was used as the reference group. Two reviewers independently extracted the information on study design, participant characteristics, level of alcohol consumption, stroke outcome, control for potential confounding factors, risk estimates and key criteria of study quality using a standardized protocol. RESULTS: The dose-response relationship for hemorrhagic stroke had monotonically increasing risk for increasing consumption, whereas ischemic stroke showed a curvilinear relationship, with a protective effect of alcohol for low to moderate consumption, and increased risk for higher exposure. For more than 3 drinks on average/day, in general women had higher risks than men, and the risks for mortality were higher compared to the risks for morbidity. CONCLUSIONS: These results indicate that heavy alcohol consumption increases the relative risk of any stroke while light or moderate alcohol consumption may be protective against ischemic stroke. Preventive measures that should be initiated are discussed.

Investigadores de la Universidad de Toronto, Canadá, y la Universidad de Dresde, Alemania, llevaron a cabo un meta-análisis para evaluar sistemáticamente los efectos de bebidas alcohólicas en cantidad y en el tipo y el riesgo de padecer accidentes cerebrovasculares, con el objetivo de proporcionar las estimaciones del riesgo basado en el nivel de alcohol. Los resultados publicados recientemente indican una constante asociación entre el consumo excesivo de alcohol y el riesgo de ambos tipos de accidente cerebrovascular. En la relación dosis-respuesta para un accidente cerebrovascular hemorrágico se observó un riesgo que aumentaba constantemente al aumentar el consumo. Por el contrario, una relación de curva-J se observó para los accidentes cerebrovascular isquémicos, se observó un efecto protector para cantidades de bajas a moderadas de alcohol y un riesgo creciente con grandes cantidades. En general, con un promedio de más de 3 bebidas / día, las mujeres tenían un riesgo mayor que los hombres, y el riesgo de mortalidad fue mayor en comparación con el riesgo de morbilidad. En otras palabras: un consumo moderado de hasta a 3 bebidas al día protege contra accidentes cerebrovascular isquémicos, pero el efecto es neutral para accidentes hemorrágicos cerebrovasculares.

Researchers from the University of Toronto, Canada, and the University of Dresden, Germany, carried out a meta-analysis to systematically assess the impact of alcoholic beverages on both, the type and outcome of stroke, and to provide risk estimates based on the level of alcohol. The recently published results suggest a consistent association between heavy drinking and risk for both types of stroke. The dose response relationship for hemorrhagic stroke showed a steadily rising risk for increasing consumption. In contrast, a J-curved relationship was observed with ischemic stroke, with a protective effect of low to moderate amounts of alcohol and an increasing risk for a higher exposure. In general, with more than 3 drinks on average/day, women had a higher risk than men, and the mortality risk was higher compared to the morbidity risk. In other words: a moderate consumption of up to 3 drinks per day is protective for ischemic stroke but neutral for hemorrhagic stroke.