High and moderate alcohol use linked to increase risk of stroke

No link to low intake or to people who formerly drank, finds research co-led by the University of Galway

Heavy and even moderate drinkers are at an increased risk of stroke, a global study led by the University of Galway has found.

While high and moderate intake of alcohol increases the odds of stroke, no link was found with low intake, according to the 27-country study.

Former drinkers are also not at increased risk of stroke, the researchers found.

The study, published in the journal Neurology, looked at the alcohol consumption of almost 26,000 people globally, of whom one quarter were current drinkers, and two-thirds of whom never drank. They came from a range of ethnic backgrounds in the 27 countries, which included Ireland.

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Those classified as “current drinkers” were linked to a 14 per cent increase in odds of all stroke and a 50 per cent increase in odds of intra-cerebral haemorrhage (stroke due to bleeding), but there was no increase in risk of ischaemic stroke (stroke due to clots).

Heavy episodic or binge drinking was linked with a 39 per cent increase in all stroke, a 29 per cent increase in ischaemic stroke and a 76 per cent increase in intra-cerebral haemorrhage. High alcohol intake was linked with a 57 per cent increase in stroke.

The Interstroke study, which is the largest study of risk factors for the condition, also looked at differences between types of alcohol. Predominant beer consumption was linked with a 21 per cent increase in risk of stroke, and this was significantly higher (73 per cent) for intra-cerebral haemorrhage. Predominant wine consumption was not linked with risk of stroke – there was no increase or decrease.

Up to now, there has been uncertainty about the association between alcohol consumption and stroke, especially around low and moderate intake, according to Prof Martin O’Donnell, professor of neurovascular medicine at University of Galway, who led the study in partnership with scientists from McMaster University in Canada.

“The findings indicate that high and moderate intake of alcohol were associated with increased odds of stroke, while we found no convincing link between low intake and stroke.”

Stroke is a leading cause of death and disability globally. Each year, approximately 7,500 Irish people have a stroke, and about 2,000 of these people die. An estimated 30,000 people in Ireland are living with disabilities as a result of stroke.

Low alcohol intake is defined as one to seven drinks a week; moderate as seven to 14 drinks for females and seven to 21 for males; high intake as over 14 drinks for females and over 21 for males.

Unlike most previous studies, this one included high, middle and lower income countries with varying levels of education and cardiovascular risk profiles.

“Current drinking was linked with reduced risk of stroke in western Europe and North America, but increased risk of stroke in India and South America,” according to geriatrician Prof Michelle Canavan. “The greatest increases in stroke risk were seen for binge drinkers in South America, Africa and India and with those who have high levels of alcohol consumption in China and South East Asia.

“Therefore, targeted interventions to manage high intake at population level may help reduce stroke risk, particularly for males in these regions who are more likely to binge drink.”

Paul Cullen

Paul Cullen

Paul Cullen is a former heath editor of The Irish Times.