Associations between short-term exposure to air pollution, extreme temperature events and coronary heart disease mortality: A seven-year time-series study in Wuhan, China

Evidence has shown that air pollution exposure and extreme temperature events (ETEs) were both associated with coronary heart disease (CHD) mortality, but their interaction was less appreciated. This study was to explore the individual and joint effects of air pollution and ETEs on CHD mortality. Numbers of Daily deaths from CHD were collected between 1st January 2013 and 31st December 2019. Daily mean levels of five air pollutants and daily mean temperature in Wuhan were also collected during the study period. We used generalized additive models with a quasi-Poisson distribution to fit the relationships between air pollution and CHD mortality. While distributed lag non-linear models were performed to explore the relationship between ETEs and CHD mortality. The interaction effect between air pollution and ETEs was considered by relative risk due to interaction (RERI), attributable proportion (AP) and Synergy index (S). In this study, a total of 51,247 CHD deaths were observed. We noticed that short-term exposure to PM10, NO2 and SO2 was positively associated with the elevated risk of CHD mortality. The relative risks (RR) for CHD mortality were 1.004 (1.001, 1.007), 1.011 (1.005, 1.016) and 1.015 (1.004, 1.026) with a 10 μg/m3 increment in PM10, NO2 and SO2, respectively. Besides, heatwave and cold spell events were both associated with a higher risk of CHD death [RR=1.202 (1.025, 1.410) for heatwave (HW09); RR=1.199 (1.078, 1.335) for cold spell (CS01)]. There were synergetic effects on CHD mortality between heatwave and PM10 with RERI=0.37 (0.22, 0.53). Short-term exposure to ambient PM10, NO2, SO2 and ETEs was associated with an elevated risk of death from CHD with a lag effect. There is a synergetic effect of heatwave and PM10 on CHD mortality.