Associations between short-term exposure to PM2.5 and stroke incidence and mortality in China: A case-crossover study and estimation of the burden

Stroke and fine particulate matter (PM₂.₅) are two important public health concerns worldwide. Although numerous studies have reported the associations between PM₂.₅ and stroke, scientific evidence in China is incomplete, particularly the effect of PM₂.₅ on the acute incidence and national acute health burdens of stroke attributed to PM₂.₅ pollution. This study identified about 131,947 registered patients and 23,018 deaths due to stroke in 10 counties located in various regions from 2013 to 2017. Using a time-stratified case-crossover design, this study evaluated the associations between short-term exposure to PM₂.₅ and the risks of acute incidence and mortality for different types of stroke on the same spatiotemporal scale. With a 10 μg/m³ increase in the PM₂.₅ concentration, the acute incidence risk increased by 0.37% (0.15%, 0.60%) for stroke, 0.46% (0.21%, 0.72%) for ischemic stroke, and −0.13% (−0.73%, 0.48%) for hemorrhagic stroke. The corresponding values for the mortality risk were 0.71% (0.08%, 1.33%), 1.09% (0.05%, 2.14%), and 0.43% (−0.44%, 1.31%) for stroke, ischemic stroke and hemorrhagic stroke, respectively. Compared with the other groups, females and patients aged over 64 years presented higher incidence and mortality risks, while the group aged >75 years may exhibit a greater risk of mortality. Based on the estimated effects, we evaluated 43,300 excess deaths and 48,800 acute incidences attributed to short-term PM₂.₅ exposure across China in 2015. This study provided robust estimates of PM₂.₅-induced stroke incidence and mortality risks, and susceptible populations were identified. Excess mortality and morbidity attributed to short-term PM₂.₅ exposure indicate the necessity to implement health care and prevention strategies, as well as medical resource allocation for noncommunicable diseases in regions with high levels of air pollution.