Short-term effects of ambient temperature and pollutants on the mortality of respiratory diseases: A time-series analysis in Hefei, China

Background: The air pollution has become an important environmental health problem due to its adverse health effect. The objective of this study was to investigate the effects of ambient temperature and pollutants on mortality of respiratory diseases (RD) in Hefei, China, a typical inland city. Methods: Nonlinear exposure–response dependencies and delayed effects of urban daily mean temperature (DMT) and pollutants were evaluated by distributed lag non-linear models (DLNM). To further explore this effect, different genders and ages were also examined by stratified analysis. Results: A total of 12876 deaths from RD were collected from January 1, 2014 to December 31, 2018 in Hefei, China. There was a U-shaped correlation between DMT and RD mortality, and the RD mortality rised by 11.6% (95% CI: 2.2–22.0%) when the DMT was 35.8 °C (reference temperature is 20 °C). The results show that risk of death with short-term exposure to elevated concentrations of PM10 and SO2 was not significant. The maximum hysteresis and cumulative relative risk (RR) of RD mortality were 1.012 (95% CI: 1.003 ~ 1.021, lag 0 day) and 1.072 (95% CI: 1.014 ~1.133, lag 10 days) for each 10 μg/m3 augment in NO2; 1.005 (95% CI: 1.001–1.009, lag 0 day) and 1.027 (95% CI: 1.004–1.051, lag 10 days) for each 10 μg/m3 augment in O3; a negative association between CO exposure and the cumulative risk of death was observed (RR = 0.964, 95% CI: 0.935–0.993, lag 07 days). Subgroup analysis showed the effect of high temperatures, NO2, O3 and CO exposure was still statistically significant for the elderly and male. Conclusion: The present study found that short-term exposure to high temperature, NO2, O3 and CO were significantly associated with the risk of RD mortality and male as well as elderly are more susceptible to these factors