Background:
Cohort studies on the association between long-term exposure to fine particulate matter (PM2.5) and mortality have been well established for America and Europe, but limited and inconsistent in Asia with much higher air pollution. This study aims to investigate the associations between ambient PM2.5 and all-cause and cause-specific mortality over a period of rising and then declining PM2.5.
Methods:
We enrolled a total of 400,459 adults from an open cohort between 2001 and 2016, and followed them up until 31 May 2019. We obtained mortality data from the National Death Registry maintained by the Ministry of Health and Welfare in Taiwan. We estimated ambient PM2.5 exposures using a satellite-based spatiotemporal model. We performed a Cox regression model with time-dependent covariates to investigate the associations of PM2.5 with deaths from all causes and specific causes.
Results:
This study identified 14,627 deaths and had a total of 5 million person–years of follow-up. Each 10µg/m3 increase in PM2.5 was associated with an increased hazard risk (HR) of 29% (95% confidence interval [CI]: 24%-35%) in all-cause mortality. Risk of death increased by 30% for natural causes, 20% for cancer, 42% for cardiovascular disease (CVD) causes, and 53% for influenza and pneumonia causes, for each 10µg/m3 increase in PM2.5. Sensitivity analyses generally yielded similar results.
Conclusion:
Long-term exposure to ambient PM2.5 was associated with increased risks of all-cause mortality and deaths from cancers, natural causes, CVD, and influenza and pneumonia. Longitudinal study design should be encouraged for air pollution epidemiologic investigation.
Funding: This work was in part supported by RGC-General Research Fund (14603019) and Environmental Health Research Fund of the Chinese University of Hong Kong (7104946). Cui Guo is in part supported by the RGC Postdoctoral Fellowship Scheme of Hong Kong. Yacong Bo is in part supported by the Faculty Postdoctoral Fellowship Scheme of the Faculty of Medicine of the Chinese University of Hong Kong.
Conflict of Interest: The authors declare that they have no conflicting interests related to this manuscript.
Acknowledgments: We would like to thank MJ Health Research Foundation for the authorization of using MJ health data (authorization code: MJHR2019006A). Any interpretation or conclusion related to this manuscript does not represent the views of MJ Health Research Foundation. We also thank the Health and Welfare Data Science Center, Ministry of Health and Welfare in Taiwan for the help of mortality data linkage. We are grateful to the anonymous reviewers and editors for their valuable comments.
Availability of data and code: Data are available from the corresponding author upon appropriate request.
Acknowledgments: We would like to thank MJ Health Research Foundation for the authorization of using MJ health data (authorization code: MJHR2019006A). Any interpretation or conclusion related to this manuscript does not represent the views of MJ Health Research Foundation. We also thank the Health and Welfare Data Science Center, Ministry of Health and Welfare in Taiwan for the help of mortality data linkage. We are grateful to the anonymous reviewers and editors for their valuable comments.
Ethics approval: This study is approved by the Joint Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee and the National Cheng Kung University in Tainan, Taiwan.
Corresponding author: Xiang Qian Lao, Ph.D.; Institute: Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong; Address: 421, 4/F School of Public Health, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, China. Tel: +852 2252 8763. Fax: +852 2606 3500. E-mail: xqlao@cuhk.edu.hk
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