Differentiating the effects of fine and coarse particulate air pollution on the onset of stable and unstable angina: a case-crossover study in 305 Chinese cities

Background and purpose: Associations between fine and coarse particulate matters (i.e., PM2.5 and PM2.5–10, respectively) and the onset of angina have rarely been investigated. We aimed to systematically explore the impacts of PM2.5 as well as PM2.5–10 on the onset of stable and unstable angina at the hourly timescale. Methods: We performed a time-stratified case-crossover study among 995,734 angina patients from 1,655 hospitals in 305 Chinese cities from January 2015 to December 2021. Concentrations of PM2.5 and PM2.5–10 were collected at the hourly timescale from nearby fixed-site monitoring stations. Hourly onset information of unstable and stable angina was obtained from the Chinese Cardiovascular Association Database-Chest Pain Center. We applied conditional logistic regressions combined with polynomial distributed lag models to explore the lagged exposure–response associations. Subgroup analyses were performed to explore potential effect modifiers including age, sex, season, and region. Results: Transient exposure to PM2.5 was significantly associated with elevated risk of unstable and stable angina onset. The associations occurred immediately in the concurrent hour of exposure, attenuated thereafter, and turned to null at approximately lag 12 h for unstable angina and 9 h for stable angina. Each interquartile range increase in the PM2.5 concentrations over 0 to 12 h was associated with 1.32% (95% confidence interval [95% CI]: 0.94%–1.70%) and 1.69% (95% CI: 0.99%–2.39%) increase in the onset risk of unstable and stable angina, respectively. The results remained similar after controlling for co-pollutants. Greater magnitudes of associations were found among females and during cold season. Null associations were observed between PM2.5–10 and any type of angina. Conclusion: Our study indicates that acute exposure to PM2.5, rather than PM2.5–10, was significantly associated with the onset of both unstable and stable angina, underscoring the need of continued efforts in controlling particulate matter air pollution.