Sex-specific difference of the association between ambient air pollution and the prevalence of obesity in Chinese adults from a high pollution range area: 33 Communities Chinese Health Study
Introduction
Well documented by scholars as of late has been an escalating global epidemic of obesity -“globesity”- which has increased dramatically across many parts of the world (Dong et al., 2014, IASO, 2009); Lifshitz and Lifshitz, 2014, Mitchell et al., 2011). Some have suggested that if recent secular trends continue unabated, by 2030 there would be approximately 2.16 billion overweight individuals and roughly 1.12 billion obese individuals (Kelly et al., 2008). Because obesity is broadly associated with a host of deleterious problems (Arnold et al., 2015, Berrington et al., 2010, Flegal et al., 2013, Whitlock et al., 2009), scientists have devoted a significant amount of time to unpacking the causes of the obesity epidemic in an attempt to curtail what is becoming a global issue. Importantly, scholars have begun pushing beyond the traditional correlates of obesity such as dietary factors (McAllister et al., 2009), and have started to explore the role that environmental toxins and pathogens may play in the development of obesity more closely (Blumberg et al., 2011, Keith et al., 2006).
In recent years, the relationship between air pollution and obesity has caught scientists’ interest. Rundle et al. (2012) found that maternal exposure to air polycyclic aromatic hydrocarbons (PAH) during pregnancy is positively correlated with increased body mass index (BMI) and obesity by age seven in children. A more recent study suggested that exposure to near-roadway pollution is also a contributing factor in the development of childhood obesity (Jerrett et al., 2014). Experimental evidence has revealed that ambient particle (diameter, <2.5 μm [PM2.5]) exposure is capable of inducing metabolic abnormalities and obesity in non-human subjects (rodents) (Xu et al., 2010). Taken together, these findings suggest that ambient air pollution may be a factor that is associated with the development of obesity.
Despite increased interest in the air pollution-obesity link, there remains limited evidence in humans generated from large epidemiological samples. Dong et al. (2014), analyzing a sample of Chinese children between the ages of 2 and 14 years old, provided evidence that exposure to a range of pollutants (including particulate matter, ozone, and sodium dioxide) was positively related to obesity even after adjusting for a host of possible confounders. Building on the work of these scholars, the 33 Communities Chinese Health Study (33CCHS) provides an additional and ideal opportunity to examine the association between air pollution exposure and obesity in Chinese adults in an area experiencing high levels of air pollution. In the present analysis, we hypothesize that exposure to ambient air pollution is associated with a higher prevalence of obesity among adults.
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Site selection and participant recruitment
The study setting for the 33 Communities Chinese Health Study (33CHS) is Liaoning province, which is located in northeast China and is comprised of over 20 million people in 14 cities. The study sites and participant recruitment have been reported in greater detail elsewhere (Dong et al., 2013a, Zhao et al., 2013). In April 2009, we selected three cities (Shenyang, Anshan, and Jinzhou) based on the results of air pollution measurements taken between 2006 and 2008 to maximize the inter- and
Study participants
Out of a total of 28,830 participants randomly selected from the 33 communities within the three cities, 24,845 participants completed the survey and examination. The response rate was 86.2%. The mean age of the participants was 45.6 years (SD = 13.3 years) and 12,661 (50.1%) were men. The sample characteristics, stratified by bodyweight categories, are shown in Table 1. Among the participants, 35.3% (8760) were overweight and 5.8% (1435) were obese. There was an increasing proportion of family
Discussion
As we have indicated previously (Dong et al., 2013a), the average levels of PM10 and SO2 were between 2.5 and 6 times higher than the WHO recommended limits using the current sample. The findings of the present study were consistent with our initial hypothesis that there is a positive correlation between exposure to long-term ambient air pollution and obesity after controlling for a net of possible confounders.
As we mentioned earlier, there remains a limited amount of research on this specific
Conclusions
Ultimately, our results suggest that exposure to higher concentrations of various pollutants correlate positively with being overweight and obese among adults in the study sample, who were all between the ages of 18 and 74. In order to confirm the association and develop evidence that more directly addresses causality, more research is needed.
Disclosure
The authors report no conflicts of interest to declare.
Acknowledgments
The authors acknowledge the cooperation of the seven cities, school principals, teachers, and students and their parents. This research was supported by grants from China Environmental Protection Foundation (CEPF2008-123-1-5), the Liaoning Province Science and Technology Foundation (2013225049), and the Guangdong Province Natural Science Foundation (2014A050503027). The authors report no competing financial interest.
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