Associations of long-term exposure to fine particle and its components with ischemic stroke: A cohort study in China

Several studies have demonstrated that prolonged exposure to PM_2.5 is associated with elevated risks of developing ischemic stroke (IS). However, evidence on the association of PM_2.5 components with IS is still lacking. Thus, we aimed to estimate the association of 15 chemical components of PM_2.5 with risk of IS in a cohort study.

A community-based prospective cohort study comprising 29,926 participants was conducted in Yinzhou district, Ningbo, China. We utilized a land-use regression model to calculate the concentrations of PM_2.5 and its 15 components. Adaptive elastic net (AENET) models were used to select important components from 135 predictors and environmental risk score (ERS) was calculated to quantify the multi-pollutant combined effect. Cox proportional hazard models and restricted cubic splines were used to estimate the associations of PM_2.5 components with the occurrence of IS.

During 156,694 person-years of follow-up period, 770 new IS cases were identified. In single pollutant model, every IQR increased in PM_2.5 (HR=1.240, 95 % CI: 1.098-1.401) and mercury (HR=1.441, 95 % CI: 1.240-1.675) was positively associated with risk of IS, whereas every IQR increased in cadmium (HR=0.935, 95 % CI: 0.900-0.971), antimony (HR=0.867, 95 % CI: 0.761-0.987), selenium (HR=0.700, 95 % CI: 0.611-0.802), and ammonium (HR=0.797, 95 % CI: 0.709-0.897) were inversely associated with IS. ERS was constructed by AENET according to 3 main effects (lead, selenium, and thallium), 3 square terms (beryllium, cadmium, and selenium), and 2 component-component interactions (beryllium × mercury and cadmium × selenium). A higher ERS was associated with a higher risk of IS (every IQR increased: HR=1.429, 95 % CI: 1.275-1.601).

Long-term exposure to PM_2.5 and its constituents may increase the risk of IS. Three heavy metals in PM_2.5 from soil dust and coal combustion (lead, selenium, and cadmium), as well as three from non-ferrous metallurgy (thallium, beryllium, and mercury), contributed the most.