Academic journal article Environmental Health Perspectives

Risk of Incident Diabetes in Relation to Long-Term Exposure to Fine Particulate Matter in Ontario, Canada

Academic journal article Environmental Health Perspectives

Risk of Incident Diabetes in Relation to Long-Term Exposure to Fine Particulate Matter in Ontario, Canada

Article excerpt

Diabetes mellitus and its associated macrovascular (Kannel and McGee 1979; Manson et al. 1991a) and microvascular (Watkins and Edmonds 1983) complications constitute a serious threat to global human health and welfare (Wild et al. 2004). The burden of diabetes relates particularly to type 2 diabetes, which accounts for 90-95% of cases globally (American Diabetes Association 2012). Although obesity (Colditz et al. 1995), diet (Hu et al. 2001), and physical inactivity (Manson et al. 1991b) have been identified as important risk factors for type 2 diabetes, there is increasing evidence that insulin resistance, the underlying hallmark and pathophysiological mechanism leading to type 2 diabetes, can be aggravated by factors that promote inflammatory responses (Hotamisligil 2006).

It is only recently that ambient air pollution has been implicated in the etiology of type 2 diabetes (Brook et al. 2008). Exposure to air pollution has been associated with cardiovascular-related mortality and morbidity (Brook et al. 2010; Chen et al. 2008). There is also evidence that persons with diabetes are particularly susceptible to the acute effects of air pollution (Goldberg et al. 2006; O'Neill et al. 2005). In a mouse model, exposure to fine particulate matter (particles with an aerodynamic diameter [less than or equal to] 2.5 [micro]m; [PM.sub.2.5]) increased blood glucose and induced adipose inflammation and insulin resistance (Sun et al. 2009). This animal study provides a potential biological basis for the link between air pollution and diabetes.

Because of the ubiquitous nature of exposure to air pollution, even a modest effect of air pollution on increasing the risk of diabetes may pose a large public health burden. To date, only four epidemiological studies have investigated the relationship between air pollution and incident diabetes (Andersen et al. 2012; Coogan et al. 2012; Kramer et al. 2010; Puett et al. 2011). Two reported positive associations between incident diabetes and [PM.sub.2.5] and traffic-related pollutants such as nitrogen oxides (N[O.sub.x]) and nitrogen dioxide (N[O.sub.2]) (Coogan et al. 2012; Kramer et al. 2010). However, another study reported no association between incident diabetes and [PM.sub.2.5] (Puett et al. 2011), and the fourth reported only a small increase in diabetes associated with NO2 (Andersen et al. 2012). Of the four cohort studies, one was based on a general population (Andersen et al. 2012), two included women only (Coogan et al. 2012; Kramer et al. 2010), and one comprised female nurses and male health professionals (Puett et al. 2011).

Given that few epidemiological studies have examined associations between air pollution and diabetes, and because little is known about the association in the general population, we conducted a population-based cohort study of long-term exposure to [PM.sub.2.5] and incident diabetes in Ontario, Canada.

Materials and Methods

Study design and population. The study was designed as a follow-up of respondents from Ontario, Canada, to the 1996/1997 cycle of National Population Health Survey of all Canadians (Statistics Canada 2010a) and the 2000/2001, 2002, 2003, and 2005 cycles of the Canadian Community Health Surveys among Canadians [greater than or equal to] 12 years of age (Statistics Canada 2010b). These population-based surveys collected information related to health status, health care utilization, and determinants of health for the Canadian population in all provinces and territories, excluding fulltime members of the Canadian military, institutional residents, and individuals living on Indian Reserves, Crown Lands, and certain remote regions. The same questions were used across surveys. The response rates of the surveys in Ontario varied from 73.4 to 92.8%, depending on the year (Statistics Canada 2010a, 2010b). The surveys have been used in health research, such as estimating the burden of cardiovascular diseases in Canada (Manuel et al. …

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