Significant mortality, morbidity, and financial burden are caused by stroke, a major subtype of cardiovascular disease (CVD). Even though the incidence of stroke has decreased over the past few decades, recent plateaus point to reasons other than conventional risk factors. Through inflammatory and vascular pathways, air pollution, especially fine particulate matter (PM2.5), has been linked to an increased risk of cardiovascular disease and stroke.
Although PM2.5 levels were lowered by regulations, wildfires brought on by climate change are reversing this trend in some areas of the United States. Intense, frequent PM2.5 exposures from wildfires are more harmful than those from other causes and may have long-term consequences on the brain. However, earlier research frequently used imprecise exposure measurements, which illuminated the necessity of high-resolution PM2.5 data unique to wildfires in order to precisely determine long-term stroke risk. Therefore this study looked at the relationship between incident stroke in older US individuals and long-term exposure to PM2.5 from wildfire smoke.
Between 2007 and 2018, Medicare Fee-for-Service beneficiaries who were 65 years of age or older participated in a nationwide open cohort research. Validated Medicare claims were used to identify stroke cases. A machine learning model that separated smoke-specific PM2.5 from other ambient sources was used to estimate wildfire smoke PM2.5 exposure at a resolution of 1 km2. Hazard ratios (HRs) per 1 µg/m3 increase in wildfire smoke PM2.5 were estimated using stratified Cox proportional hazards models with generalized estimating equations, controlling for non-smoke PM2.5, meteorological factors, socioeconomic status, and healthcare capacity.
There were around 2.9 million incident stroke cases among the approximately 25 million enrollees. Long-term exposure to PM2.5 from wildfire smoke was substantially linked to a higher risk of stroke. Longer exposure windows showed stronger correlations. For example, the incidence of stroke increased by 1.3% for every 1 µg/m3 rise in the 3-year average wildfire smoke PM2.5 (HR: 1.013; 95% CI: 1.006, 1.020).
When compared to non-smoke PM2.5 per unit exposure, associations for wildfire smoke PM2.5 were often greater. Overall, this study offers compelling evidence that long-term exposure to PM2.5 from wildfire smoke raises the risk of stroke.
Source:
Hao, H., Xu, K., Zhang, D., Deng, Y., Benmarhnia, T., Pu, Q., Pattisapu, V. K., Steenland, K., Chang, H. H., Alonso, A., & Liu, Y. (2026). Long-term exposure to wildfire smoke particulate matter and incident stroke: a US nationwide study. European Heart Journal, ehaf875. https://doi.org/10.1093/eurheartj/ehaf875
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