Same 10 modifiable risk factors for stroke span the globe, but with regional variations

Worldwide, researchers have discovered 10 modifiable risk factors that are responsible for 9 of 10 strokes, but the prioritization of these risk factors varies regionally, according to study results published in The Lancet from researchers at the Population Health Research Institute (PHRI) at McMaster University, in Hamilton, Ontario, Canada.

The study was conducted in collaboration with researchers from 32 other countries, and adds to the initial findings from the first phase of the INTERSTROKE study, in which the 10 modifiable risk factors were identified using data from 6,000 subjects from 22 different countries.

In this next phase, the full-scale phase of the INTERSTROKE study, researchers included an additional 20,000 subjects from 32 countries in Europe, Asia, America, Africa, and Australia, to discover the main causes of stroke in diverse populations, within differing stroke subtypes, in both young and old, and men and women.

“This study has the size and scope to explore stroke risk factors in all major regions of the world and within key populations,” said PHRI principal investigator Martin O’Donnell, MB, MRCPI, associate clinical professor, McMaster University, and professor of translational medicine, HRB-Clinical Research Facility, NUI Galway, Galway, Ireland.

“We have confirmed the 10 modifiable risk factors associated with 90% of stroke cases in all regions, young and older and in men and women. The study also confirms that hypertension is the most important modifiable risk factor in all regions, and the key target in reducing the burden of stroke globally,” he added.

After assessing these different risk factors, and analyzing the proportion of strokes preventable when the risk factors were removed, they found that if hypertension were eliminated, the number of strokes would be reduced by a full 48%. Other risk factor modifications also resulted in the following reductions in stroke:

• If subjects were physically active, 36%;
• If diets were improved, 19%;
• If smoking were eliminated, 12%;
• Elimination of cardiac causes, 9%;
• Elimination of diabetes, 4%;
• Reduced alcohol intake, 6%;
• Reduction of stress, 6%; and
• Better apolipoprotein levels; 27%.

Many of these risk factors were interrelated, and when combined, brought about a 91% reduction in stroke, similar in all regions, age groups, and independent of sex.

Additionally however, researchers found that some of these factors varied according to region:

• In Western Europe, North American, and Australia, the importance of hypertension was 40%, compared with 60% in Southeast Asia.
• Alcohol risk was lowest in Western Europe, North America, and Australia, and highest in Africa and South Asia. In China, the impact of physical inactivity was the greatest.
• In all regions, atrial fibrillation was associated with ischemic stroke, but in Western Europe, North America, and Australia, it was of greater importance compared with China or South Asia.
• The collective importance was similar in all regions when the 10 risk factors were included together.

“Our findings will inform the development of global population-level interventions to reduce stroke, and how such programs may be tailored to individual regions,” said Salim Yusuf, MD, DPhil, MRCP, professor of medicine, McMaster’s Michael G. DeGroote School of Medicine, and director of the PHRI.

“This includes better health education, more affordable healthy food, avoidance of tobacco, and more affordable medication for hypertension and dyslipidemia,” he concluded.