Moderate alcohol consumption – including beer – decreases the risk of ischemic stroke and has no adverse effect on other types of stroke. This is the conclusion of a recent meta-analysis published in the scientific journal BMC Medicine.
Beer and stroke
The Scandinavian researchers1 analysed 27 different studies on three types of stroke (ischemic stroke, intracerebral or subarachnoid haemorrhage). Light alcohol consumption (<1 standard glass/day) was associated with a lower relative risk of 10%, moderate alcohol consumption (1-2 standard glasses/day) with a lower relative risk of 8%. Light-to-moderate alcohol consumption was not associated with any haemorrhagic stroke subtype. High alcohol consumption (>2-4 standard glasses/day) was associated with increased risk of all three stroke types with a stronger association for haemorrhagic strokes.
Previous meta-analyses on alcohol consumption and stroke risk showed inconsistent results. This is the first meta-analysis that examined the effect of alcohol consumption on different types of stroke instead of only the effect on total stroke (ischemic and all haemorrhagic strokes combined). Since the recent meta-analysis shows that alcohol consumption has divergent effects on different stroke types, this may explain some of the inconsistent results from previous studies associating alcohol consumption with all strokes.
Type of stroke
Ischemic stroke occurs when an artery to the brain is blocked by a blood clot. It accounts for 87% of all stroke cases. Haemorrhagic stroke occurs when a weakened blood vessel ruptures. It accounts for 13% of all stroke cases. The difference between intracerebral or subarachnoid haemorrhage is the place where the bleeding occurs: intracerebral haemorrhage occurs within the cerebrum or brain, subarachnoid haemorrhage in the area between the brain and the skull (the subarachnoid space)2.
The difference in cause (obstruction or rupture of the artery) may explain the divergent effect of moderate alcohol consumption. Alcohol consumption is associated with increased high-density lipoprotein cholesterol levels and reduced fibrinogen levels3-6 and this might explain the lower risk of ischemic stroke but not the effects of light and moderate alcohol consumption associated with haemorrhagic stroke. More research regarding this specific underlying mechanism is needed.
- Susanna C. Larsson, Alice Wallin, Alicja Wolk and Hugh S. Markus, Differing association of alcoholconsumption with different stroke types:a systematic review and meta-analysis, BMC Medicine (2016) 14:178 DOI 10.1186/s12916-016-0721-4
- http://www.strokecenter.org/patients/about-stroke/ Visited on 30-11-2016
- Mukamal KJ, Rimm EB. Alcohol consumption: risks and benefits. Curr Atheroscler Rep. 2008;10:536–43.
- O’Keefe JH, Bybee KA, Lavie CJ. Alcohol and cardiovascular health: the razor-sharp double-edged sword. J Am Coll Cardiol. 2007;50:1009–14.
- Agarwal DP. Cardioprotective effects of light-moderate consumption of alcohol: a review of putative mechanisms. Alcohol Alcohol. 2002;37:409–15.
- Brien SE, Ronksley PE, Turner BJ, Mukamal KJ, Ghali WA. Effect of alcohol consumption on biological markers associated with risk of coronary heart disease: systematic review and meta-analysis of interventional studies. BMJ. 2011;342:d636.