The short-term effects of air pollutants on respiratory disease mortality in Wuhan, China: comparison of time-series and case-crossover analyses

Xi Chen,Meng Ren,Zhongmin Zhu,Xiangyu Li,Na Li,Hao Xiang,Zhan Wang,Yuanyuan Chu,Yisi Liu,Liqiao Tian

doi:10.1038/srep40482

Abstract

Few studies have compared different methods when exploring the short-term effects of air pollutants on respiratory disease mortality in Wuhan, China. This study assesses the association between air pollutants and respiratory disease mortality with both time-series and time-stratified–case-crossover designs. The generalized additive model (GAM) and the conditional logistic regression model were used to assess the short-term effects of air pollutants on respiratory disease mortality. Stratified analyses were performed by age, sex, and diseases. A 10 μg/m3 increment in SO2 level was associated with an increase in relative risk for all respiratory disease mortality of 2.4% and 1.9% in the case-crossover and time-series analyses in single pollutant models, respectively. Strong evidence of an association between NO2 and daily respiratory disease mortality among men or people older than 65 years was found in the case-crossover study. There was a positive association between air pollutants and respiratory disease mortality in Wuhan, China. Both time-series and case-crossover analyses consistently reveal the association between three air pollutants and respiratory disease mortality. The estimates of association between air pollution and respiratory disease mortality from the case–crossover analysis displayed greater variation than that from the time-series analysis.

Highlights

Time-series and case-crossover analyses are two common epidemiology methods that are frequently used to assess the health effects of air pollution
From January 1, 2007, to December 31, 2009, there were a total of 19,948 deaths, of which 2,120 were due to respiratory diseases
The results show that mortality differed based on sex and age, and a greater number of deaths were found in men and subjects older than 65 years

Summary

Introduction

Time-series and case-crossover analyses are two common epidemiology methods that are frequently used to assess the health effects of air pollution. The case-crossover design compares exposure during a case day when events occurred (e.g., deaths) with exposures in nearby control days to examine whether the events are associated with a particular exposure[16]. It has the advantage of controlling time-invariant individual confounders, www.nature.com/scientificreports/. Since time-series and case-crossover analyses are viewed as competing methods in air pollution epidemiology, the study examined whether these methods produced equivalent risk estimates

Methods

Results

Conclusion