Interactive Effect of Air Temperature and Fine Particulate Matter on the Hospital Admissions for Stroke in Shenzhen, China.

Background: Stroke is a major health challenge in China. Numerous studies have linked stroke with temperature and fine particulate matter (PM_2.5), but findings varied by stroke subtypes and regions, and few explored the interactive effects of air temperature and PM_2.5. This study examines the association between air temperature, PM_2.5, and stroke hospital admissions in Shenzhen, a subtropical monsoon city in southern China.

Methods and results: We applied time-series generalized additive models to estimate the individual and interactive effects of air temperature and PM_2.5 on stroke hospital admissions using daily records from 2015 to 2016. Subgroup analysis by sex, age, and education level was conducted, assessing admissions for hemorrhagic (n=8752) and ischemic (n=33 233) stroke separately. For hemorrhagic stroke, a 1 °C increase in temperature was significantly associated with a 2.3% (95% CI, -3.2% to -1.3%) decrease in hospital admissions, whereas higher levels of PM_2.5 indicated an increased risk, though not significant. Conversely, for ischemic stroke, a 1 °C rise was significantly associated with a 1.0% (95% CI, 0.4%-1.6%) increase in admissions. The impact PM_2.5 on stroke was more pronounced at higher concentrations, while showing no evident effects at lower levels. Interaction effects between temperature and PM_2.5 were statistically significant for both stroke types, with stronger effects observed at 10 to 20 °C and PM_2.5 concentration around 80 to 100 μg/m³.

Conclusions: This study suggests lower air temperature may increase hemorrhagic stroke risk, whereas higher temperature and higher PM_2.5 exposure may increase ischemic stroke risk. Interactive effects between temperature and PM_2.5 were observed for both stroke types in Shenzhen.