Lancet: 10 factors account for 90% of stroke risk

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Ten risk factors including hypertension, smoking, lack of exercise and diabetes, among others, account for 90 percent of stroke risk factors, according to results of the INTERSTROKE study published online June 18 in the Lancet.

“The contribution of various risk factors to the burden of stroke worldwide is unknown, particularly in countries of low and middle income where the largest burden of stroke occurs,” the authors wrote.

Martin J. O’Donnell, PhD, from McMaster University in Hamilton, Ontario, and the National University of Ireland in Galway, and colleagues set out to assess the known risk factors often linked to stroke and evaluate these risk factors compared to those commonly associated with MI.

In the INTERSTROKE study, O’Donnell and colleagues conducted a case-control study of 22 countries between March 1, 2007 and April 23, 2007, to help understand risk factors for stroke, ischemic stroke and intracerebral hemorrhagic stroke.

The researchers looked at patients with acute first stroke within five days of the onset of symptoms and within 72 hours of hospital admissions. The patients were administered questionnaires, given  physicals and also produced blood and urine samples to be used during the study.

The researchers assessed 3,000 patients with stroke—78 percent with ischemic stroke and 22 percent with cerebral hemorrhagic stroke—and 3,000 patients with no history of stroke.

After analysis, researchers found hypertension, smoking, waist-to-hip ratio, diet, diabetes mellitus, physical activity, alcohol consumption, psychosocial stress and depression and ratio of apolipoproteins B to A1 (lipids) and cardiac causes to be significant risk factors for stroke.

Additionally, researchers found that the population-attributed risks for cardiac causes, hypertension, smoking and diabetes were 6.7, 34.6, 18.9 and 5 percent, respectively.

Lack of regular physical activity exhibited the second highest population-attributed risk rates behind hypertension, 28.5 percent. Hypertension increased the risk of stroke by over two folds and accounted for one-third of the risk of stroke.

Overall, the aforementioned risk factors accounted for 88.1 percent of the population-attributed risk for all strokes.

“These risk factors were all significant for ischemic stroke, whereas hypertension, smoking, waist-to-hip ratio, diet and alcohol intake were significant risk factors for intracerebral hemorrhagic stroke,” the authors wrote.

The risk factors were all significant to cause ischemic stroke, but the authors found that blood lipids was a significant risk factor for ischemic stroke but not hemorrhagic stroke.

“Our findings suggest that ten risk factors are associated with 90 percent of the risk of stroke,” the authors concluded. “Targeted interventions that reduce blood pressure and smoking and promote physical activity and a healthy diet could substantially reduce the burden of stroke.”

The 22 countries included in the study were: Argentina, Australia, Brazil, Canada, Chile, China, Colombia, Croatia, Denmark, Ecuador, Germany, India, Iran, Malaysia, Mozambique, Nigeria, Peru, Philippines, Poland, South Africa, Sudan and Uganda.

Funding from the study came from the Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, Canadian Stroke Network, Pfizer, Merck, AstraZeneca and Boehringer Ingelheim.