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new study says low to moderate alcohol consumption does not protect against stroke

It has previously been claimed that a small amount of alcohol might protect against stroke.  A new genetic study of 160,000 people, published in The Lancet, suggests that this is not the case, and that even low levels of drinking increase the risk of stroke and heart disease.

Previous studies have been observational, so it has been difficult to distinguish whether the apparent protective effect is because moderate alcohol consumption itself protects against stroke or because of other factors – e.g. that the higher risk of stroke in non-drinkers might be because they have other underlying health problems or because they were formally heavy drinkers.

This new study uses the statistical technique of Mendelian randomisation to examine the effects of alcohol on a Chinese population, where genetic variants greatly alter alcohol tolerability.  This allows the researchers to use genetic analysis as a tool to help form random groups of individuals, just as in a randomised trial.  By comparing the health outcomes of drinkers and non-drinkers according to their genetic profile, the researchers say they have been able to make a much more definitive assessment of the causal effects of alcohol on stroke. 

The authors came to the SMC to discuss their methodology, how confident we should be in these new findings compared to what’s gone before, and how they translate to other populations.


Dr Iona Millwood, Senior Epidemiologist at the Medical Research Council Population Health Research Unit, University of Oxford

Prof Sir Richard Peto, Professor of Medical Statistics & Epidemiology and Co-Director of the Clinical Trial Service Unit, University of Oxford

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