Short-term exposure to ambient air pollution and readmissions for heart failure among 3660 post-discharge patients with hypertension in older Chinese adults

Background Despite ambient air pollution being associated with various adverse cardiovascular outcomes, the acute effects of ambient air pollution on hospital readmissions for heart failure (HF) among post-discharge patients with hypertension remain less understood. Methods We conducted a time-stratified case-crossover study among 3660 subjects 60 years or older who were admitted to hospital for HF after discharge for hypertension in Guangzhou, China during 2016-2019. For each subject, individualised residential exposures to ambient particulate matter with an aerodynamic diameter <= 1 mu m (PM1), <= 2.5 mu m (PM2.5), <= 10 mu m (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone were extracted from our validated grid dataset. Results An IQR increase of lag 04-day exposure to PM1 (IQR: 11.6 mu g/m(3)), PM2.5 (IQR 21.9 mu g/m(3)), PM10 (IQR 35.0 mu g/m(3)), SO2 (IQR 4.4 mu g/m(3)), NO2 (IQR 23.3 mu g/m(3)) and CO (IQR 0.25 mg/m(3)) was significantly associated with a 9.77% (95% CI 2.21% to 17.89%), 8.74% (95% CI 1.05% to 17.00%), 13.93% (95% CI 5.36% to 23.20%), 10.81% (95% CI 1.82% to 20.60%), 14.97% (95% CI 8.05% to 22.34%) and 7.37% (95% CI 0.98% to 14.16%) increase in odds of HF readmissions, respectively. With adjustment for other pollutants, the association for NO2 exposure remained stable, while the associations for PM1, PM2.5, PM10, SO2 and CO exposures became insignificant. Overall, an estimated 19.86% of HF readmissions were attributable to NO2 exposure, while reducing NO2 exposure to the WHO and China air quality standards would avoid 12.87% and 0.54% of readmissions, respectively. No susceptible populations were observed by sex, age or season. Conclusion Short-term exposure to ambient NO2 was significantly associated with an increased odds of HF readmissions among post-discharge patients with hypertension in older Chinese adults.