Short-term exposure to PM2.5 constituents and daily ischemic stroke hospitalization in the arid, semi-arid and semi-humid regions of northwest China.

Adverse effect PM_2.5 on ischemic stroke (IS) has been proved in previous studies. However, previous studies have mostly been conducted in eastern China (humid region), the health impacts of specific particulate matter constituents on IS, particularly in arid, semi-arid, and semi humid regions, remain poorly understood. We conducted a time-series study across nine districts in Gansu Province from 2015 to 2021 to evaluate the associations between short-term exposure to PM_2.5 chemical components-including sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), organic matter (OM), and black carbon (BC)-and hospital admissions for ischemic stroke. Generalized additive models were applied to estimate relative risks (RRs) of IS hospital admissions, with subgroup analyses by age, sex, and living region. Our findings demonstrated that short-term exposure to PM_2.5 and its constituents was associated with increased IS hospitalization, with the strongest associations observed on lag 0 (ions constituents) and lag 7 days (carbon-containing components). For subgroup analysis, female and individuals aged ≥ 65 years were more sensitive to PM_2.5 and its constituents. Regional analyses revealed that semi-arid region residents experienced the highest risks, while semi humid region showed relatively lower health impacts. Among all the components, NO₃^- revealed the strongest health effect. These results suggested that specific PM_2.5 constituents contribute to acute IS risks, with notable variation across demographic and geographic subgroups. Our study provides critical evidence on the cardiovascular health effects of PM_2.5 components in arid and semi-arid area around the world, underscoring the need for public health interventions and pollution mitigation strategies to protect vulnerable populations.