A global study on the causes of stroke, co-led by the University of Galway, discovered that high and moderate alcohol consumption was associated with an increased risk of stroke. The study also discovered no link between low-level drinking and stroke.
The INTERSTROKE study examined the alcohol consumption of nearly 26,000 people worldwide, one-quarter of whom were current drinkers and two-thirds were abstainers. The study included people from a variety of ethnic backgrounds from 27 countries, including Ireland and the United Kingdom. The findings were published in Neurology, the most widely read and cited neurology journal.
Professor Martin O’Donnell, Professor of Neurovascular Medicine at the University of Galway and Consultant Stroke Physician at Galway University Hospitals, co-led the international INTERSTROKE study with Professor Salim Yusuf from McMaster University’s Population Health Research Institute.
“Stroke is a leading cause of death and disability worldwide,” said Professor O’Donnell. Every year, approximately 7,500 Irish people suffer a stroke, with approximately 2,000 of these people dying. An estimated 30,000 people in Ireland are disabled as a result of a stroke. The INTERSTROKE study was designed to look at the key risk factors for stroke in different parts of the world in order to inform population-level prevention strategies. We concentrated on the relationship between alcohol consumption and stroke risk in this paper.
In this study we also looked at the differences between types of alcohol. Predominant beer consumption was linked with a 21% increase in risk of stroke; this was significantly higher (73%) for intracerebral haemorrhage. Predominant wine consumption was not linked with risk of stroke – there was no increase or decrease.Professor O’Donnell
“While excessive alcohol consumption is known to increase stroke risk, there is some uncertainty about whether moderate alcohol consumption affects stroke risk and whether the association of alcohol consumption with stroke varies by region and population.”
This study looked at these associations on a large scale, spanning 27 countries. Stroke can occur as a result of a clot (ischaemic) or bleeding (intracerebral haemorrhage). The study’s lead researcher was Professor Andrew Smyth, Professor of Clinical Epidemiology at the University of Galway, Director of the Health Research Board-Clinical Research Facility Galway, and Consultant Nephrologist at Galway University Hospitals.
“Overall, our findings indicate that high and moderate alcohol intake were associated with increased odds of stroke, while we found no convincing link between low intake and stroke,” said Professor Smyth. “However, the effects of alcohol consumption are complex because they are linked to socioeconomic factors such as education as well as a variety of lifestyle factors such as smoking, diet, and physical activity. It is critical to consider the potential consequences of what is commonly referred to as “binge drinking.” The risk of having seven drinks one day per week is likely to be greater than the risk of having one drink every day of the week.”
“In this study we also looked at the differences between types of alcohol. Predominant beer consumption was linked with a 21% increase in risk of stroke; this was significantly higher (73%) for intracerebral haemorrhage. Predominant wine consumption was not linked with risk of stroke – there was no increase or decrease. This may reflect a difference in risk by type of alcohol, or may reflect differences in the social context of consumption patterns.”
Included in the INTERSTROKE research was an analysis of people who had previously been drinkers but had stopped. The study found that they were not at increased risk of stroke.
Other findings from this research included:
- Current drinkers were linked with a 14% increase in odds of all stroke, and 50% increase in odds of intracerebral haemorrhage (stroke due to bleeding), but no increase in risk of ischaemic stroke (stroke due to clots).
- Heavy episodic or formerly termed ‘binge drinking’ – defined as more than 5 drinks in one day at least once a month – was linked with a 39% increase in all stroke; 29% increase in ischaemic stroke; and 76% increase in intracerebral haemorrhage.
- High alcohol intake – defined as more than 14 drinks/week for females and more than 21 drinks/week for males – was linked with a 57% increase in stroke.
Professor Michelle Canavan, Established Professor of Older Adult Health and Consultant Geriatrician, added: “Most previous research was completed in high-income countries, with limited cultural diversity whereas the global INTERSTROKE study took a different approach by including participants from high, middle and lower income countries with varying levels of education and cardiovascular risk profiles.
“Alcohol consumption varies by gender, age, social class, education, and occupation, as well as the type of alcohol consumed and the pattern of drinking. Current alcohol consumption was associated with a lower risk of stroke in Western Europe and North America, but a higher risk of stroke in India and South America. The greatest increases in stroke risk were seen in binge drinkers in South America, Africa, and India, as well as those who consume a lot of alcohol in China and Southeast Asia. As a result, population-level interventions to manage high intake may help reduce stroke risk, particularly among males in these regions who are more likely to binge drink.”