Elsevier

Environment International

Volumes 92–93, July–August 2016, Pages 416-421
Environment International

Associations between long-term exposure to ambient particulate air pollution and type 2 diabetes prevalence, blood glucose and glycosylated hemoglobin levels in China

https://doi.org/10.1016/j.envint.2016.03.028Get rights and content

Highlights

  • Limited evidence on the PM2.5-diabetes association in developing countries

  • A nationwide cross-sectional study based on a representative cohort in China

  • PM2.5 was associated with increased diabetes prevalence.

  • PM2.5 was associated with increased levels of fasting glucose and HbA1c.

Abstract

Background

The evidence for an association between particulate air pollution and type 2 diabetes mellitus (T2DM) in developing countries was very scarce.

Objective

To investigate the associations of long-term exposure to fine particulate matter (PM2.5) with T2DM prevalence and with fasting glucose and glycosylated hemoglobin (HbA1c) levels in China.

Methods

This is a cross-sectional study based on a nation-wide baseline survey of 11,847 adults who participated in the China Health and Retirement Longitudinal Study from June 2011 to March 2012. The average residential exposure to PM2.5 for each participant in the same period was estimated using a satellite-based spatial statistical model. We determined the association between PM2.5 and T2DM prevalence by multivariable logistic regression models. We also evaluated the association between PM2.5 and fasting glucose and HbA1c levels using multivariable linear regression models. Stratification analyses were conducted to explore potential effect modification.

Results

We identified 1760 cases of T2DM, corresponding to 14.9% of the study population. The average PM2.5 exposure for all participants was 72.6 μg/m3 during the study period. An interquartile range increase in PM2.5 (41.1 μg/m3) was significantly associated with increased T2DM prevalence (prevalence ratio, PR = 1.14), and elevated levels of fasting glucose (0.26 mmol/L) and HbA1c (0.08%). The associations of PM2.5 with T2DM prevalence and with fasting glucose and HbA1c were stronger in several subgroups.

Conclusions

This nationwide cross-sectional study suggested that long-term exposure to PM2.5 might increase the risk of T2DM in China.

Introduction

Type 2 diabetes mellitus (T2DM) is a long-term metabolic disorder that is primarily characterized by insulin resistance, relative insulin deficiency, and hyperglycemia. A high fasting blood glucose level was ranked as the 7th risk factor for global disease burden and accounted for 3.4 million deaths (Lim et al., 2012). It was estimated that 590 million people would be suffering from T2DM by the year 2035 (Guariguata et al., 2014). It is also an important risk factor for cardiovascular diseases, leading to enormous health consequences. Furthermore, the development of these outcomes in people with diabetes may be exacerbated by exposure to exogenous toxic factors (Zanobetti and Schwartz, 2001).

There is growing evidence from both human and animal studies suggesting that particulate matter (PM) air pollution is an important risk factor for T2DM (Balti et al., 2014, Esposito et al., 2016, Eze et al., 2015, Liu et al., 2013, Park and Wang, 2014). Dozens of cross-sectional and cohort studies have reported a positive association between long-term exposure to ambient PM and risk for T2DM (Janghorbani et al., 2014, Li et al., 2014, Wang et al., 2014), but some other studies did not find such a relationship. For example, using two large prospective cohorts, the Nurses' Health Study and the Health Professionals Follow-Up Study, Puett et al. failed to find strong evidence of an association between exposure to PM in the previous 12 months and incident diabetes (Puett et al., 2011). Additionally, studies have focused on the effects of PM on the incidence, prevalence and mortality of T2DM, but few have explored its effects on glucose homeostatic measures, such as fasting glucose and glycosylated hemoglobin (HbA1c) levels (Rajagopalan and Brook, 2012). HbA1c is a well-acknowledged marker for measuring the average plasma glucose concentration over prolonged periods, and an elevated HbA1c level denotes an increased risk of developing diabetes and its complications (Edelman et al., 2004, Gillett, 2009). Furthermore, most studies on the associations between PM and T2DM were conducted in North America and Europe, and the evidence has been very limited in developing countries, where a steep increase in T2DM was observed in the past few decades and where the air pollution level is much higher (Nicole, 2015).

As the largest developing country, China is facing a growing prevalence of diabetes and severe air pollution problems (Yang et al., 2013). Given the vast population affected by diabetes and the ubiquitous exposure to air pollution, it is of increasing public health significance to examine the impacts of PM on diabetes. Therefore, the objective of this study was to evaluate the association of long-term exposure to PM with T2DM and with fasting blood glucose and HbA1c levels in China. This study was based on a nationally representative survey of the China Health and Retirement Longitudinal Study (CHARLS) project (Zhao et al., 2014), which aimed to provide a high-quality public database with a wide range of information to facilitate needs of scientific and policy research on ageing-related issues.

Section snippets

Study population and health data

This is a cross-sectional study based on a national baseline survey within the CHARLS project. This baseline survey was conducted from June 2011 to March 2012 and included 17,708 middle-aged and elderly participants (≥ 45 years old) (Zhao et al., 2014). Briefly, these participants were selected from 150 counties or districts from 28 provinces using a four-staged, stratified and cluster sampling method. Individual information on sociodemographic characteristics, behaviors, indoor air pollution and

Descriptive statistics

The weighted descriptive statistics on sociodemographic characteristics, behaviors, and indoor air pollution of the study population (n = 11.847) are summarized in Table 1. For example, the age range of the participants was 45 to 99, with an average of 59. There were similar proportions of males and females (48.0% VS 52.0%). According to the main definition, the prevalence of T2DM in the study population was 15.8%, which was comparable to that (11.6%) reported in another nationwide survey in 2010

Discussion

To our knowledge, this was the largest epidemiological study to explore the association between long-term PM2.5 exposure and T2DM in a developing country. Our findings showed that long-term exposure to PM2.5 was positively associated with significant increases in diabetes prevalence, fasting glucose and HbA1c levels. These associations were robust to different definitions of diabetes, exposure modeling methods and the exclusion of one person from each spouse pair.

The number of studies on the

Conclusions

In conclusion, this nationwide cross-sectional study suggested that long-term exposure to PM2.5 might increase the risk of T2DM in China. Our findings demonstrated that particulate air pollution was an important modifiable environmental factor contributing to the development and prevalence of diabetes in China. Therefore, there is an urgent need to reduce particulate air pollution in this country where the prevalence of diabetes was growing rapidly.

Acknowledgements

The study was supported by the Public Welfare Research Program of National Health and Family Planning Commission of China (201502003), National Institute on Aging (1R01AG037031-03S and R03AG049144), the National Natural Science Foundation of China (71130002 and 71450001), China Medical Board Collaborating Program (13-152 and 13-154), the World Bank (7172961), the Shanghai 3-Year Public Health Action Plan (GWTD2015S04) and the National Natural Science Foundation of China (81502774).

The authors

References (42)

  • G. Cesaroni et al.

    Nitrogen dioxide levels estimated from land use regression models several years apart and association with mortality in a large cohort study

    Environ. Health

    (2012)
  • L. Chen et al.

    Air pollution and fasting blood glucose: a longitudinal study in China

    Sci. Total Environ.

    (2015)
  • K.J. Chuang et al.

    Long-term air pollution exposure and risk factors for cardiovascular diseases among the elderly in Taiwan

    Occup. Environ. Med.

    (2011)
  • D. Edelman et al.

    Utility of hemoglobin A1c in predicting diabetes risk

    J. Gen. Intern. Med.

    (2004)
  • K. Esposito et al.

    Particulate matter pollutants and risk of type 2 diabetes: a time for concern?

    Endocrine

    (2016)
  • I.C. Eze et al.

    Association between ambient air pollution and diabetes mellitus in Europe and North America: systematic review and meta-analysis

    Environ. Health Perspect.

    (2015)
  • A.F. Fleisch et al.

    Air pollution exposure and abnormal glucose tolerance during pregnancy: the project Viva cohort

    Environ. Health Perspect.

    (2014)
  • U. Gehring et al.

    Long-term exposure to ambient air pollution and cardiopulmonary mortality in women

    Epidemiology

    (2006)
  • M.J. Gillett

    International Expert Committee report on the role of the A1c assay in the diagnosis of diabetes: diabetes care 2009; 32(7): 1327-1334

    Clin. Biochem. Rev.

    (2009)
  • J. Gulliver et al.

    Development and back-extrapolation of NO2 land use regression models for historic exposure assessment in Great Britain

    Environ. Sci. Technol.

    (2013)
  • M. Janghorbani et al.

    Systematic review and metaanalysis of air pollution exposure and risk of diabetes

    Eur. J. Epidemiol.

    (2014)
  • Cited by (0)

    1

    Cong Liu and Changyuan Yang contributed equally to this work.

    View full text