The adverse effect of alcohol consumption on blood pressure a major risk factor for stroke may increase the risk of hemorrhagic stroke.
Alcohol has varied effect in the types of stroke as light and moderate alcohol consumption of up to two drinks per day is associated with a lower risk of ischemic stroke but seems to have no effect on a person's risk of hemorrhagic stroke, according to a study published in the open access journal BMC Medicine. Researchers at Karolinska Institute, Sweden, and University of Cambridge, UK, suggest that the divergent associations of alcohol consumption with different types of stroke may explain some of the inconsistent findings of previous studies which investigated the association between alcohol consumption and stroke but did not discriminate between different stroke types.
‘Heavy drinkers were about 1.6 times more likely to suffer from intracerebral hemorrhage and 1.8 times more likely to suffer from subarachnoid hemorrhage.’
Dr. Susanna Larsson, lead author said: "This is the first study that combines the results from all available prospective studies on alcohol consumption and risk of hemorrhagic stroke subtypes. Our results showed that heavy drinkers were about 1.6 times more likely to suffer from intracerebral hemorrhage and 1.8 times more likely to suffer from subarachnoid hemorrhage. The association between heavy alcohol consumption and these two types of stroke was stronger than that for ischemic stroke." Ischemic stroke is caused by blood clots which block diseased or damaged cerebral arteries. Hemorrhagic stroke occurs when a weakened blood vessel, such as an aneurism, bursts and bleeds either within the brain (intracerebral) or -- less commonly -- into the space between two membranes that surround the brain (subarachnoid).
The researchers suggest that different associations between alcohol consumption and type of stroke may have to do with the effects alcohol has on the human body.
Dr. Larsson explained: "Previous research has found an association between alcohol consumption and lower levels of fibrinogen -- a protein in the body which helps the formation of blood clots. While this may explain the association between light to moderate alcohol consumption and lower ischemic stroke risk, the adverse effect of alcohol consumption on blood pressure -- a major risk factor for stroke - may increase the risk of hemorrhagic stroke and outweigh any potential benefit".
To examine the association of alcohol consumption with different stroke types, the researchers conducted a systematic review and meta-analysis of 25 prospective studies with data on ischemic stroke, intracerebral hemorrhage and subarachnoid hemorrhage.
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Alcohol consumption across all studies was assessed with a questionnaire or by interview and standardized to drinks of alcohol. Exposure categories were light (<1 drink per day), moderate (1-2 drinks per day), high (2-4 drinks per day) and heavy (more than four drinks per day).
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Also, the possibility that the associations of light and moderate alcohol consumption with stroke risks have been overestimated due to the small sample sizes of some of the included studies cannot be ruled out.
Most of the studies included in this meta-analysis adjusted for major potential confounders such as age, sex, smoking, body mass index, and diabetes. However, observational studies can show a possible association between alcohol consumption and risk of different types of stroke, but they cannot show cause and effect because other factors may have impacted the results.
Source-Medindia