Long-term exposure to ambient fine particulate matter (PM2.5) and incident type 2 diabetes: a longitudinal cohort study
Information on the associations of long-term exposure to fine particulate matter (with an aerodynamic diameter less than 2.5 μm; PM2.5) with the development of type 2 diabetes is scarce, especially for south-east Asia, where most countries are experiencing serious air pollution. This study aimed to investigate the long-term effects of exposure to ambient PM2.5 on the incidence of type 2 diabetes in a population of Taiwanese adults.
A total of 147,908 participants without diabetes, at least 18 years of age, were recruited in a standard medical examination programme between 2001 and 2014. They were encouraged to take medical examinations periodically and underwent at least two measurements of fasting plasma glucose (FPG). Incident type 2 diabetes was identified as FPG ≥7 mmol/l or self-reported physician-diagnosed diabetes in the subsequent medical visits. The PM2.5 concentration at each participant’s address was estimated using a satellite-based spatiotemporal model with a resolution of 1 × 1 km2. The 2 year average of PM2.5 concentrations (i.e. the year of and the year before the medical examination) was treated as an indicator of long-term exposure to ambient PM2.5 air pollution. We performed Cox regression models with time-dependent covariates to analyse the long-term effects of exposure to PM2.5 on the incidence of type 2 diabetes. A wide range of covariates were introduced in the models to control for potential effects, including age, sex, education, season, year, smoking status, alcohol drinking, physical activity, vegetable intake, fruit intake, occupational exposure, BMI, hypertension and dyslipidaemia (all were treated as time-dependent covariates except for sex).
Compared with the participants exposed to the first quartile of ambient PM2.5, participants exposed to the second, third and fourth quartiles of ambient PM2.5 had HRs of 1.28 (95% CI 1.18, 1.39), 1.27 (95% CI 1.17, 1.38) and 1.16 (95% CI 1.07, 1.26), respectively, for the incidence of type 2 diabetes. Participants who drank occasionally or regularly (more than once per week) or who had a lower BMI (<23 kg/m2) were more sensitive to the long-term effects of exposure to ambient PM2.5.
Long-term exposure to ambient PM2.5 appears to be associated with a higher risk of developing type 2 diabetes in this Asian population experiencing high levels of air pollution.
KeywordsIncident type 2 diabetes Longitudinal cohort Long-term exposure PM2.5
Aerosol optical depth
Fasting plasma glucose
Metabolic equivalent value
Particulate matter with an aerodynamic diameter less than 2.5 μm
We appreciate the MJ Health Research Foundation for authorising the use of its health data (authorisation code: MJHR2015002A). We are grateful to the anonymous reviewers and the editors for their valuable comments.
XQL conceived and designed the study and obtained the funding. L-YC, AKHL and XQL supervised this study. L-YC, AKHL and XQL acquired the data. CG, YB and ZZ searched the literature. ZZ, YB, YCC and WKJ cleaned the data. CL and AKHL estimated the PM2.5 concentration. CG analysed the data. CG, XQL, TT, C-YL and TCC interpreted the results. CG and XQL drafted the manuscript. XQL, CG, TT, C-YL and TCC revised the manuscript. All authors contributed to the content and critical revision of the manuscript and agreed to submit the manuscript for publication. XQL is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
This work was in part supported by the Environmental Health Research Fund of the Chinese University of Hong Kong (7104946). CG and YB are supported by the PhD Studentship of the Chinese University of Hong Kong.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
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