Global Stroke Burden Continues to Rise, With Climate Change Gaining Influence

Even as stroke rates have come down around the world, an aging population has continued to push the total burden in terms of absolute numbers ever higher, which threatens to overwhelm the healthcare system over the coming decades.

That’s one of the key takeaways of the latest stroke update from the Global Burden of Disease, Injuries, and Risk Factors (GBD) study, published last week in the Lancet Neurology.

In addition, the link between stroke and climate change-related factors—like ambient temperature and air pollution—appears to be getting stronger, lead author Valery Feigin, MD, PhD (National Institute for Stroke and Applied Neurosciences, Auckland University of Technology, New Zealand), and colleagues report.

The GBD Study is the only project that provides information on the burden of stroke across all countries and territories, as well as trends over the last 30 years, Feigin told TCTMD. “Without that study,” he added, “any healthcare planning, resource allocations, and priority settings are not really evidence-based, so regular updates of these estimates are absolutely crucial for public health.”

The continuing rise in global stroke burden indicates that approaches to managing the problem need to change, including by moving away from common risk-based efforts that have the medical community focusing on individuals deemed to be at highest risk, he argued.

“Priority should be given to primary prevention,” Feigin said. “We’re always kind of reacting to the situation. We need proactive actions, and this is prevention. That’s the only way we can stop a rise in the burden and eventually reverse it.”

The Key Role of Environmental Factors

Prior GBD analyses have shown that the prevalence of cardiovascular diseases, including stroke, increased steadily between 1990 and 2019, with an overall slowing of the decline in CVD-related mortality—and increases in some parts of the world—over time. Moreover, a previous stroke-related analysis with data through 2019 demonstrated that stroke remained the second leading cause of death in the world behind ischemic heart disease. Feigin and his colleagues subsequently projected large increases in stroke-related mortality and disability-adjusted life-years (DALYs)—a measure encompassing years at full health that are lost—by 2050.

In their current paper, the investigators provide an update on the situation using data gathered through 2021 from 204 countries and territories. In addition to stroke events, they examined changes in 23 individual risk factors and six risk clusters (ie, air pollution, tobacco smoking, and behavioral, dietary, environmental, and metabolic factors) across 21 GBD regions and sociodemographic index quintiles.

There is no country in the world where the burden in absolute terms is going down. Valery Feigin

Not surprisingly, Feigin said, stroke burden continued to rise on a global scale, even as rates of new and prevalent cases, deaths, and DALYs stayed on the decline in most areas. In 2021, there were an estimated 11.9 million new stroke events (up 70.2% from 1990), 93.8 million stroke survivors (up 86.1%), 7.3 million related deaths (up 44.1%), and 160.5 million related DALYs (up 32.2%) worldwide.

The heaviest impact was felt in low- and middle-income countries, which accounted for 83.3% of incident cases, 76.7% of prevalent cases, 87.2% of fatal cases, and 89.4% of stroke-related DALYs.

Stroke was bumped from second to third on the list of overall causes of death (after ischemic heart disease and COVID-19) and from the third- to the fourth-leading cause of DALYs (behind COVID-19, ischemic heart disease, and neonatal disorders).

More unexpected data came in the form of the most influential risk factors for stroke, Feigin said. High systolic BP was still at the top, accounting for 56.8% of stroke-related DALYs, but coming in second and third were ambient particulate matter pollution (16.6% of DALYs) and smoking (13.8% of DALYs). Although both of those were important contributors in prior analyses, they hadn’t been ranked as highly, Feigin noted.

Moreover, the updated data indicate that extreme high ambient temperatures are having a profound impact on stroke burden, adding to prior studies showing the importance also of extreme cold temperatures.

“These findings are in line with research showing that rises in ambient temperature (including heat waves) and climate change are associated with increased stroke morbidity and mortality,” the authors write. “Because ambient air pollution is reciprocally associated with the ambient temperature and climate change, all of which synergistically influence cardiovascular disease (including stroke) occurrence and overall health, the importance of urgent climate actions and measures to reduce ambient air pollution cannot be overestimated.”

Redoubling Primary Prevention Efforts

The current approach of screening for individuals at highest risk of stroke and focusing management efforts on them—and spending less time on lower-risk individuals—is clearly not working to reduce burden around the world, Feigin said, noting that most people who have cardiovascular events would be deemed to be at low or moderate risk.

He pointed to a 2021 report from the World Health Organization (WHO) that concluded that screening for CVD risk and CVD risk factors has had no impact on lowering CVD morbidity and mortality in the general population. In some cases, in fact, such efforts may increase mortality, the WHO said.

“That’s one of the reasons I believe we are failing in primary prevention of stroke and cardiovascular disease, and that needs to be changed,” Feigin said.

Last year, a World Stroke Organization-Lancet Neurology commission, which Feigin helped lead, offered potential solutions to reduce the global burden of stroke, with recommendations covering four main areas—surveillance, prevention, acute care, and rehabilitation. To raise funding for these efforts, they advise taxing unhealthy products.

“That’s what we need to be implementing as fast as we can across the globe if you want to change the situation,” Feigin said, adding that the public health community needs to recognize that after age 70, neurological events overtake cardiac events in terms of prevalence.

If greater attention isn’t paid to stroke, he said, “the whole health system will be at risk because we only have an increase in the burden. There is no country in the world where the burden in absolute terms is going down.”

In an accompanying editorial, Simiao Wu, MD, PhD, and Ming Liu, MD (both from West China Hospital, Sichuan University, Chengdu, China), say “the GBD estimates, although sometimes incomplete or inconsistent, help to fill the data gap and raise awareness and inform the direction for current practice and future research.”

They add, “We hope that GBD analyses will continue to provide timely health data and inform action in the battle against stroke at the global, regional, and national levels.”