9 out of every 10 strokes are preventable, study suggests

Nine out of every 10 strokes has a modifiable risk factor, including hypertension, a new study suggests. Stroke is the fifth leading cause of death in the United States, where about 800,000 Americans suffer a stroke each year, according to the Centers for Disease Control and Prevention.

For the research, published Friday in The Lancet, scientists analyzed nearly 27,000 people from every continent in the world and found that 10 factors accounted for 90 percent of stroke risk in all regions. The relative role of each factor on stroke risk varied by region, and study authors said those observations could inform governments’ approach to the disease.

Researchers’ findings build upon previous conclusions drawn from the INTERSTROKE study, which identified 10 modifiable risk factors for stroke in about 6,000 participants from 22 countries, according to a news release. They studied an additional 20,000 people in 32 countries to identify the main causes of stroke in diverse populations and within subtypes of stroke.

The two major types of stroke are ischaemic stroke, which is caused by blood clots and accounts for 85 percent of the incidents, and haemorrhagic stroke, or bleeding in the brain, which comprises 15 percent of strokes.

To estimate each risk factor’s effect on stroke risk, study authors calculated each one’s population attributable risk (PAR), a measurement used to determine how eliminating an individual risk factor could impact an overall disease burden.

Study authors found that the PAR was about 48 percent for hypertension— making it the biggest risk factor for stroke— about 36 percent for physical inactivity, about 23 percent for poor diet, 19 percent for obesity, 12 percent for smoking, 9 percent for heart causes, 4 percent for diabetes, 6 percent for alcohol intake, 6 percent for stress, and 27 percent for lipids. Some factors, like obesity and diabetes, are already associated with one another. When combined, the total PAR for all 10 risk factors was about 90 percent— an estimate that was similar among all regions, age groups, and in men and women.

In North America, the PAR for hypertension was 39 percent but nearly 60 percent in Southeast Asia. The PAR for alcohol intake was lowest in western Europe, North America and Australia but highest in Africa and South Asia. The PAR for physical inactivity was highest in China.

“Our findings will inform the development of global population-level interventions to reduce stroke, and how such programs may be tailored to individual regions, as we did observe some regional differences in the importance of some risk factors by region,” study author Salim Yusuf, a professor at the Population Health Research Institute at McMaster University, said in the release. “This includes better health education, more affordable healthy food, avoidance of tobacco and more affordable medication for hypertension and dyslipidaemia”