Air pollution, high temperatures, and metabolic risk factors are driving global increases in stroke, contributing to 12 million cases and more than 7 million deaths from stroke each year, new data from the Global Burden of Disease (GBD) study showed.
Between 1990 and 2021, the number of people who experienced a stroke increased to 11.9 million (up by 70% since 1990), while the number of stroke survivors rose to 93.8 million (up by 86%), and stroke-related deaths rose to 7.3 million (up by 44%), making stroke the third leading cause of death worldwide after ischemic heart disease and COVID-19, investigators found.
Stroke is highly preventable, the investigators noted, with 84% of the stroke burden in 2021 attributable to 23 modifiable risk factors, including air pollution, excess body weight, high blood pressure, smoking, and physical inactivity.
This means there are “tremendous opportunities to alter the trajectory of stroke risk for the next generation,” Catherine O. Johnson, MPH, PhD, co-author and lead research scientist at the Institute for Health Metrics and Evaluation (IHME), University of Washington, Seattle, said in a news release.
The study was published online in The Lancet Neurology.
Top Risk Factor for Subarachnoid Hemorrhage
Since 1990, the contribution of high temperatures to poor health and early death due to stroke has risen 72%, a trend likely to increase in the future — underscoring the impact of environmental factors on the growing stroke burden, the authors said.
“Given that ambient air pollution is reciprocally linked with ambient temperature and climate change, the importance of urgent climate actions and measures to reduce air pollution cannot be overestimated,” Dr. Johnson said.
Mitchell S.V. Elkind, MD, MS, chief clinical science officer for the American Heart Association, who wasn’t involved in the study, told this news organization that environmental factors such as air pollution, particulate matter from wildfires and other sources, and excessive heat are now recognized as major contributors to the risk for stroke. “This should not be surprising as we have long recognized the risks of stroke associated with toxins in cigarette smoke, which likely share mechanisms for vascular damage with pollutants,” Dr. Elkind said.
The data also reveal for the first time that ambient particulate matter air pollution is a top risk factor for subarachnoid hemorrhage, contributing to 14% of the death and disability caused by this serious stroke subtype, on a par with smoking.
Dr. Elkind noted that smoking is “a major risk factor for subarachnoid hemorrhage. It makes sense that particulate air pollution would therefore similarly be a risk factor for subarachnoid hemorrhage, which similarly damages blood vessels. Prior studies were likely too small or did not assess the role of air pollution in subarachnoid hemorrhage.”
The analysis also showed substantial increases between 1990 and 2021 in the global stroke burden linked to high body mass index (up by 88%), high blood sugar (up 32%), a diet high in sugar-sweetened drinks (up 23%), low physical activity (up 11%), high systolic blood pressure (up 7%), and a diet low in omega-6 polyunsaturated fatty acids (up 5%).
“And with increasing exposure to risk factors such as high blood sugar and diet high in sugar-sweetened drinks, there is a critical need for interventions focused on obesity and metabolic syndromes,” Dr. Johnson said.
“Identifying sustainable ways to work with communities to take action to prevent and control modifiable risk factors for stroke is essential to address this growing crisis,” she added.