Role of stroke risk factors identified in Irish-led study

THE IMPORTANCE of different factors putting people at risk of stroke has been identified for the first time in a major global research project led by an Irish expert in the disease.

The Interstroke study found a common heart rhythm disorder that causes stroke is four times more common in developed countries such as Ireland.

Martin O’Donnell, professor of translational medicine at the Health Research Board (HRB) clinical research facility at NUI Galway, who presented the findings at the World Congress of Cardiology in Beijing yesterday, led researchers from 22 countries who looked at 3,000 patients who had had their first stroke, and compared them with a similar number of healthy control patients.

High blood pressure, smoking, abdominal obesity, raised blood lipids and physical inactivity are the most important modifiable risk factors for stroke, the researchers found. These are also risk factors for heart attack, but the study has identified differences in the relative importance of each.

It found that uncontrolled blood pressure is the most important risk for stroke, while elevated blood fats such as cholesterol pose the biggest risk for heart attack.

The study looked at regional variations in risk factors. “One striking finding was the regional variation in atrial fibrillation, irregular heart rhythm, which was four times more common in western countries compared to Asia.

“Importantly, the risk of stroke associated with atrial fibrillation can be reduced substantially with antithrombotic therapy,” said Prof O’Donnell, who is also a stroke physician at University Hospital Galway.

Asked how the findings might influence the new national cardiovascular strategy published last week, he told The Irish Times: "Based on our findings, successful implementation of the cardiovascular strategy is expected to have a considerable impact on the incidence of stroke in Ireland.

“In particular, improving detection and treatment of blood pressure needs to be a central focus, as it is the most important risk factor for stroke.”

Dr O’Donnell carried out the research with Dr Salim Yusuf at McMaster University in Hamilton, Canada. He confirmed he will continue as the lead investigator from Galway when the next phase of the research, looking at 20,000 participants, begins later this year.

The study, published online by the Lancetyesterday to coincide with its presentation in China, identified 10 risk factors for stroke: high blood pressure, smoking, abdominal obesity, diet, physical activity, lipids, diabetes, alcohol intake, stress and depression, and certain heart disorders.

In an accompanying commentary, Dr Jack V Tu of the University of Toronto, said: “Whilst hypertension is well established as the most important cause of stroke in high-income countries, Interstroke confirms that it is also the most important risk factor for stroke in developing countries.

“This finding is particularly relevant, because it highlights the need for health authorities in these regions to develop strategies to screen the general population for high blood pressure.”

There are two types of stroke, which occur when the blood supply to the brain is cut off.

The more common ischaemic stroke results from a blockage of arteries supplying the brain, while a haemorrhagic stroke occurs when blood vessels within the brain rupture. About 10,000 people develop a stroke in the Republic every year.

STROKE RESEARCH RISK FACTORS

High/uncontrolled blood pressure

Smoking

Abdominal obesity

Raised blood lipids such as cholesterol

Physical inactivity

Atrial fibrillation (irregular heart rhythm)

Diet

Diabetes

Alcohol intake

Stress and depression

Certain heart disorders