Depression, neighborhood deprivation and risk of type 2 diabetes

Abstract

Neighborhood characteristics have been associated with both depression and diabetes, but to date little attention has been paid to whether the association between depression and diabetes varies across different types of neighborhoods. This prospective study examined the relationship between depression, neighborhood deprivation, and risk of type 2 diabetes among 336,340 adults from a national-representative sample of primary care centers in Sweden (2001–2007). Multi-level logistic regression models were used to assess associations between depression and risk of type 2 diabetes across affluent and deprived neighborhoods. After accounting for demographic, individual-level socioeconomic, and health characteristics, depression was significantly associated with risk of diabetes (odds ratio (OR): 1.10, 95% confidence interval (CI): 1.06–1.14), as was neighborhood deprivation (OR for high vs. low deprivation: 1.66, 95% CI: 1.22–1.34). The interaction term between depression and neighborhood deprivation was non-significant, indicating that the relationship between depression and diabetes risk is similar across levels of neighborhood socioeconomic deprivation.

Introduction

Major depression and type 2 diabetes mellitus are the first and eighth leading causes of disability-adjusted life years lost among high-income countries, and are projected to be in the top ten causes of disability-adjusted life years lost worldwide by 2030 (World Health Organization, 2008). A key characteristic of depression in mid- and late-life is comorbidity with medical illness (Katz, 1996). Epidemiologic and clinical studies have established that depression often co-occurs with type 2 diabetes (Katon, 2008)^, and it is now acknowledged that this relationship is likely bi-directional (Pan et al., 2011, Pan et al., 2010, Campayo et al., 2010, Frasure-Smith et al., 2000, Mezuk et al., 2008a, Golden et al., 2008). Depression is associated with both risk of type 2 diabetes (Mezuk et al., 2008a), and poor clinical prognosis among those with diabetes (Pan et al., 2011, Lin et al., 2009, de Groot et al., 2001). However, research to date has not extensively examined whether depression may interact with other risk factors for type 2 diabetes, in particular contextual environmental characteristics.

There is a growing appreciation of the role that contextual environmental factors (e.g., “neighborhood” factors) have on mental and physical health (Shih et al., 2011, Dubowitz et al., 2011, Kim, 2008, Xue et al., 2005, Kershaw et al., 2011). Neighborhoods have both physical and social attributes that may influence health. Physical attributes include access to goods and services, greenspace, and availability of alcohol and tobacco outlets; social attributes include community unemployment, segregation, social capital, civic participation, and crime (Diez Roux and Mair, 2010). Because place of residence is strongly patterned by social position, neighborhood characteristics may be important contributors to health disparities (Diez Roux and Mair, 2010). Contextual environmental factors may influence mental and physical health by placing constraints on (or promoting) health-related behaviors (e.g., smoking, alcohol use, diet, physical activity), or through acting as a source of (or buffer against) stressors (Diez Roux and Mair, 2010). A handful of studies have prospectively examined contextual environmental characteristics and risk of depression or type 2 diabetes, with mixed results (Kim, 2008, Diez Roux and Mair, 2010). Lofors and Sundquist (2007) reported that high neighborhood deprivation was associated with 20% increased risk of in-patient hospitalization for major depression relative to more affluent neighborhoods (Lofors and Sundquist, 2007), and Crump et al. (2011) reported that individuals in high deprivation neighborhoods were 15% more likely to be prescribed antidepressants than those in affluent neighborhoods. Galea et al. (2007) reported that individuals living in the poorest neighborhoods had twice the risk of major depression relative to affluent neighborhoods (Galea et al., 2007). However, other reports have not found a significant association between the contextual environment and risk of major depression or elevated depressive symptoms (Yen and Kaplan, 1999, Schootman et al., 2007a, Wight et al., 2009) Regarding diabetes, Auchincloss et al. (2008) found that living in a neighborhood with better resources for physical activity and healthy foods was associated with lower prevalence of insulin resistance, and a 38% lower incidence of type 2 diabetes (Auchincloss et al., 2009). Other characteristics of the built environment, such as housing quality, have also been associated with risk of type 2 diabetes (Schootman et al., 2007b, Cox et al., 2007). Neighborhood deprivation and attributes of the physical environment have also been positively associated with conditions related to diabetes, particularly obesity (Mujahid et al., 2008).

Despite the epidemiologic evidence supporting major depression and depressive symptoms as a risk factor for type 2 diabetes, and the apparent association between neighborhood characteristics and these health conditions, thus far no studies have examined whether neighborhood context modifies the association between depression and risk of type 2 diabetes. Two studies have examined whether the relationship between depression and diabetes varies by individual-level indicators of socioeconomic status (Mezuk et al., 2008b, Carnethon et al., 2003), and both found that the risk of type 2 diabetes associated with depression was greatest among those with the lowest educational attainment. Not only are individuals with low educational attainment more likely to experience depression (Lorant et al., 2003), they may be less likely to have positive resources (socially or financially) to cope with a depressive episode when it occurs (Krueger and Chang, 2008). Because of their lower socioeconomic status, individuals with depression may also be more likely to live in and be exposed to environmental contexts that increase diabetes risk, such as high concentration of fast food restaurants, alcohol outlets, and tobacco shops. These contexts simultaneously promote opportunities to engage in unhealthy stress-coping behaviors (e.g., diets high in fats and sugar, smoking) and limit opportunities to engage in healthy behaviors that reduce diabetes risk through limited access to healthy foods and outdoor recreational activities (Auchincloss et al., 2008, Auchincloss et al., 2009). Over time, this may lead to an accumulation of poor health outcomes associated with depression among persons living in socially disadvantaged communities.

The aims of this study are to: (a) determine the prospective relationship between major depression, neighborhood deprivation, and type 2 diabetes, and (b) evaluate whether the relationship between major depression and risk of type 2 diabetes is moderated by contextual environmental characteristics.