Stroke Strikes One in Four Globally

About one in four people worldwide can be expected to have a stroke in their lifetime, with certain populations noticeably worse off perhaps due to a mix of lifestyle and regional sociodemographic factors, a study showed.

In 2016, lifetime stroke risk from age 25 onward was 24.9%, after adjusting for competing risks of death. That figure is up from 22.8% in 1990, found Gregory Roth, MD, of the University of Washington in Seattle, and collaborators of the Global Burden of Disease (GBD) Lifetime Risk of Stroke Study.

The sociodemographic index (SDI), an indicator of a country’s development based on income, education, and fertility, had a non-linear relationship with lifetime stroke risk, the investigators showed in the Dec. 20 issue of the New England Journal of Medicine:

• High SDI (most developed countries): 23.53%
• High-middle SDI: 31.07%
• Middle SDI: 29.30%
• Low-middle SDI: 16.76%
• Low SDI (least developed countries): 13.24%

“The societal costs associated with stroke are substantial, including the direct care costs but also the costs related to loss of productivity and employment. It appears these data should animate public health officials and other stakeholders to take bold steps to reduce risks and the burden of stroke in the years to come,” commented Shyam Prabhakaran, MD, of Northwestern Medicine in Chicago, who was not part of the study.

Geographically, the regions with the highest lifetime risk of stroke were East Asia (38.8%), Central Europe (31.7%), and Eastern Europe (31.6%). Canada and the U.S. together fell somewhere in the middle of the pack (23.8%), along with Western Europe (22.7%). Researchers found that the lowest risk was generally in sub-Saharan Africa (under 15%).

Low-SDI countries, like those in sub-Saharan Africa, are typically ones with the youngest populations due, in part, to people commonly dying from causes other than stroke; the low lifetime risk of stroke is therefore not to be taken as a signal of more effective prevention or treatment strategies, Roth’s team cautioned.

“The accuracy of the estimates of lifetime risk of stroke was limited by the accuracy and availability of epidemiologic data from the countries studied,” they acknowledged.

Diagnostic accuracy, after all, reflects access to healthcare and related technologies in a given country, commented Larry Goldstein, MD, of the University of Kentucky in Lexington. And while the study did not address the reasons for the observed trends, it could be related to changes in diagnosis or real shifts in population risk factor profiles, he said in an interview.

Accordingly, “countries that have a concentration of untreated risk factors, like hypertension and smoking, and reasonably advanced diagnostic testing and population data, like China and Eastern Europe, have the highest lifetime risks,” said Joseph Broderick, MD, of the University of Cincinnati, who was not part of the GBD study.

Overall, the study’s results are “not really a surprise” but describe in a new way the burden of stroke in a given population, he noted.

Men around the world had a 15.4% relative increase in their stroke risk from 1990 to 2016, outpacing women, whose risk grew 3.2%. The two sexes ended up with similar risks in 2016 (24.7% vs 25.1%, respectively).

By region, the biggest relative increase in risk (29.7%) occurred in East Asia. In China, a man’s lifetime risk of stroke grew to a whopping 41.1% in 2016 (36.7% for women).

At the same time, the biggest relative drops in stroke risk occurred among countries in Southern sub-Saharan Africa (-15.4%), Southern Latin America (-14.1%), and the high-income Asia-Pacific countries (-13.5%).

Less dramatically, the U.S., Canada, and Western Europe had small, less than 3% increases in stroke risk from 1990 to 2016.