90% of Stroke Worldwide Attributable to 10 Modifiable Risk Factors

A large, global study has identified 10 potentially modifiable risk factorslinked to approximately 90% of the population attributable risks (PARs) of stroke; however regional variations exist, indicating the need for global and regional primary stroke prevention initiatives.

“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,” study author Martin O’Donnell, PhD, of McMaster University in Ontario, Canada, said in a statement. “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.”

According to the Centers for Disease Control and Prevention, stroke is currently the fifth leading cause of death.

The first phase of the INTERSTROKE study, which included 6000 participants in 22 countries, found that 90% of acute ischemic strokes and intracerebral hemorrhages were associated with 10 modifiable risk factors. In the second phase, investigators sought to understand the regional and population variations in modifiable risk factors for stroke by expanding the study to 13,000 cases of acute stroke and 13,000 age- and sex-matched controls in 32 countries.

Participants with their first acute stroke were recruited from 142 centers in Africa, North America, Asia, Australia, Europe, and the Middle East. Diagnosis was based on WHO stroke criteria and severity was measured by the modified Rankin Scale. The study ultimately included 10,388 participants with ischemic stroke and 3059 participants with intracerebral hemorrhage for a total of 13,447 cases and 13,472 controls.

Factors that were associated with stroke included a history of hypertension (OR 2.98, PARs 47.9%), psychosocial factors (OR 2.20, PARs 17.4%), a higher apolipoprotein ApoB/ApoA1 ratio (OR 1.84, PARs 26.8%), higher waist to hip ratio (OR 1.44, PARs 18.6%), tobacco smoking (OR 1.67, PARs 12.4%), cardiac source (OR 3.17, PARs 9.1%), heavy alcohol use (OR 2.09, PARs 5.8%), diabetes mellitus (OR 1.16, PARs 3.9%), regular physical activity (OR 0.60, PARs 35.8%), and a healthy diet score (OR 0.60, PARs 23.2%). When data was analyzed separately, hypertension had a stronger association to intracerebral hemorrhage than ischemic stroke; however cardiac disease, smoking, diabetes, and apolipoproteins had a stronger association to ischemic stroke.

PARs for all 10 risk factors was 90.7% for all strokes, 87.1% for intracerebral hemorrhage, and 91.5% for ischemic stroke. The results were consistent for age, sex, and region.

Several regional differences highlighting the importance and prevalence of certain risk factors were observed. For instance, hypertension was associated with strokes in every region; however the PARs for current smoking was highest in North America, Australia, and Western Europe (18%) and lowest in Africa (4.5%) for stroke. Likewise, there were differences in the PARs for waist-to-hip ratio and all-stroke between Western Europe, North America, and Australia (36.7%), southeast Asia (37.2%), south Asia (32.1%), China (7.8%), and eastern/central Europe and the Middle East (2.8%). Physical activity also demonstrated a wide regional range for PARs with 4.7% in Africa and 59.9% in China. Interestingly, when the data was analyzed for daily fruit and vegetable intake, the researchers found significantly lower odds of stroke in all study regions except Africa and south Asia.

Although they identified regional and ethnic differences in the impact of certain risk factors, “the collective contribution of these 10 risk factors to stroke risk was consistent in all populations, meaning that general approaches to prevention of stroke can be similar worldwide, but population-specific refinement of programs might be needed,” the authors wrote.

The study had several limitations, particularly the case-control design which may lead to bias. Further, the authors noted that causality cannot be completely attributed to risk factors in a case-control study.

References

1. Stroke. Centers for Disease Control and Prevention website. https://www.cdc.gov/stroke/. Last updated May 5, 2016. Accessed July 24, 2016.
2. O’Donnell MJ, Chin SL, Rangarajan S, et al. Global and regional effects of potentially modifiable risk factors associated with acute stroke in 32 countries (INTERSTROKE): a case-control study. The Lancet. 2016; doi: 10.1016/S0140-6736(16)30506. 
3. Global study shows stroke largely preventable: 10 risk factors are same worldwide, with regional variation [News Release]. McMaster University. Published July 15, 2016. http://www.eurekalert.org/pub_releases/2016-07/mu-gss071416.php.