Sex differences in Associations of Fine Particulate Matter with Non-accidental Deaths: An Ecological Time-Series Study

Abstract Background: Sex differences in the impact of exposure to air pollution have been reported previously and epidemiological studies indicate that fine particulate matter (PM2.5) effects on non-accidental death are modified by sex, however, the results are not conclusive. This study aimed to investigate the sex difference in the effects of PM2.5 on non-accidental death, considering the nonlinear exposure-response relationships between PM2.5 and smoking and death.Methods: Information on daily non-accidental deaths, air pollution, meteorological data, and smoking prevalence between 1 January, 2012 and 31 December, 2014 was obtained in Shanghai, China. Constrained generalized additive models were used to assess the association of interaction between sex and daily PM2.5 concentrations with daily non-accidental deaths, adjusting for weather type and smoking rate. A two-week lag analysis was conducted as a sensitivity analysis.Results: During the study period, the total number of non-accidental deaths in Shanghai was 336,379, with a daily mean of 163 deaths and 144 deaths for men and women, respectively. The average daily concentration of PM2.5 in Shanghai was 55.0 µg/m3 during the same time period. Older people and men showed a higher risk for non-accidental death (risk ratio (RR) = 1.025 per year increase in age, 95% confidence interval (CI): 1.021 – 1.029, and RR = 0.892 for women, 95% CI: 0.802 – 0.993, respectively). Compared with men, the risk for non-accidental death in relation to increasing PM2.5 concentration was smaller in women (RR = 0.998, 95% CI: 0.996 – 1.000, per 10 µg increase in PM2.5 concentration. The difference is consistent during the two lag weeks and more obvious when adjusting for the interaction between PM2.5 concentration and smoking prevalence.Conclusion: The effects of PM2.5 on daily non-accidental death are different between men and women in Shanghai, China, and women tend to have a lower risk. The underlying mechanisms of the sex difference of PM2.5 effects on death need further investigation.