Experiences of Discrimination and Incident Type 2 Diabetes Mellitus

The Multi-Ethnic Study of Atherosclerosis (MESA)

Kara M. Whitaker; Susan A. Everson-Rose; James S. Pankow; Carlos J. Rodriguez; Tené T. Lewis; Kiarri N. Kershaw; Ana V. Diez Roux; Pamela L. Lutsey

Disclosures

Am J Epidemiol. 2017;186(4):445-455. 

In This Article

Abstract and Introduction

Abstract

Experiences of discrimination are associated with increased risk of adverse health outcomes; however, it is unknown whether discrimination is related to incident type 2 diabetes mellitus (diabetes). We investigated the associations of major experiences of discrimination (unfair treatment in 6 situations) and everyday discrimination (frequency of day-to-day experiences of unfair treatment) with incident diabetes among 5,310 participants from the Multi-Ethnic Study of Atherosclerosis, enrolled in 2000–2002. Using Cox proportional hazards models, we estimated hazard ratios and confidence intervals, adjusting for demographic factors, depressive symptoms, stress, smoking, alcohol, physical activity, diet, waist circumference, and body mass index. Over a median follow-up of 9.4 years, 654 diabetes cases were accrued. Major experiences of discrimination were associated with greater risk of incident diabetes when modeled continuously (for each additional experience of discrimination, hazard ratio = 1.09, 95% confidence interval: 1.01, 1.17) or categorically (for ≥2 experiences vs. 0, hazard ratio = 1.34, 95% confidence interval: 1.08, 1.66). Similar patterns were observed when evaluating discrimination attributed to race/ethnicity or to a combination of other sources. Everyday discrimination was not associated with incident diabetes. In conclusion, major experiences of discrimination were associated with increased risk of incident diabetes, independent of obesity or behavioral and psychosocial factors. Future research is needed to explore the mechanisms of the discrimination-diabetes relationship.

Introduction

The adverse association between discrimination and mental health is well established. Studies have identified associations of discrimination with depression, distress, anxiety, lack of well-being, and psychotic experiences.[1–4] Growing evidence also suggests that more experiences of discrimination are related to poorer physical health.[1,3] Cross-sectional and longitudinal studies have reported associations of discrimination with a wide variety of physical health outcomes, including all-cause mortality, cardiovascular disease, hypertension, breast cancer, and asthma.[5–10]

Discrimination is a form of psychosocial stress that is thought to influence health through both physiological and behavioral mechanisms. Chronic experiences of stress are considered most deleterious because they are more likely to result in long-term changes in physiological or behavioral responses that ultimately influence disease susceptibility.[11,12] This would include more subtle forms of day-to-day discrimination, as well as major experiences of discrimination that continue to have lasting consequences long after the actual experience has ended.[13] Stress leads to negative emotional states, which may trigger activation of the hypothalamic-pituitary-adrenal axis, causing an increase in glucocorticoid exposure, resulting in immunosuppression and hyperglycemia.[14,15] Stress may also influence health by leading to adverse behavioral coping responses.[1,3,16] Studies have demonstrated an association between discrimination and adverse health behaviors such as smoking, high alcohol consumption, reduced physical activity, and poor dietary habits[17–19] as well as measures of adiposity, including greater body mass index (BMI), waist circumference, and visceral fat.[20–23]

Given the mechanisms by which stress is thought to affect health, it is plausible that experiences of discrimination increase the risk of developing type 2 diabetes mellitus (diabetes). For example, discrimination may increase stress and depressive symptoms, thus leading to adverse coping behaviors, such as poor dietary habits, which increases the risk of obesity and diabetes. However, to our knowledge, no studies have examined the associations of discrimination and incident diabetes.

Furthermore, despite the increasing number of studies examining the relationship between discrimination and health, several questions remain unanswered. For example, existing research has focused largely on racial discrimination or overall mistreatment, primarily in African Americans, and less is known about other types of discrimination and physical health outcomes or whether these associations differ in other racial/ethnic groups.[1,2] Also, few studies have examined whether the association between discrimination and health differs according to whether the discrimination was due to race or other sources of unfair treatment,[6,8,24] and the evidence is not consistent as to whether chronic, everyday experiences of discrimination are more influential than major experiences of discrimination.[2] A recent review paper by Lewis et al.[4] called for additional research to disentangle the associations of different types of discrimination on health outcomes.

The purpose of this study was to evaluate whether self-reported experiences of discrimination are related to incident diabetes over a 10-year period in a population-based cohort including 4 racial/ethnic groups. We hypothesized that major experiences of discrimination and everyday discrimination are associated with a greater risk of developing diabetes. Additionally, we separately evaluated major experiences of discrimination self-attributed to race/ethnicity versus other sources in relation to diabetes risk. Given that the relationship between discrimination and adverse health events may differ by demographic characteristics, we also examined potential differences in associations of discrimination and incident diabetes by race/ethnicity, age, and sex.

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