Life Stress, Race, and Abnormal Glucose Metabolism in Postmenopausal Women.

Abstract

To the Editor: The diabetes mellitus epidemic in the United States is well documented, with an incidence that escalated from 5.6 million in 1980 to 29.1 million in 2011.1 These data are particularly alarming for postmenopausal black women, in whom the rate of diagnosis for diabetes mellitus per 100 population is 38.2, compared with 17.1 in postmenopausal white women.1 Eliminating such health disparities has become a national research priority,2 but a perplexing situation. Poverty, barriers to healthcare access, and lifestyle choices are the most commonly identified factors explaining health disparities, but these factors do not explain differences in morbidity and mortality in large population-based studies. The theory of allostatic load3 has emerged as a novel hypothesis to explain health disparities. It is proposed that the biological deterioration brought about by progressive physiological stress increases susceptibility to disease.4 It was hypothesized that chronic activation of the stress response to the discrimination that black women experience weakens physiological systems, leading to differences in postmenopausal glucose metabolism. Menopausal changes increase insulin resistance and risk of metabolic syndrome and diabetes mellitus in all women.5 During the reproductive years, estrogen decreases glucagon secretion6 to conserve energy for procreation. Menopausal loss of this estrogenic effect allows glucagon secretion, mobilizing lipids and stimulating gluconeogenesis. Glucagon also acts as an insulin antagonist, and blood glucose levels increase as a result, but estrogen decline alone does not explain racial differences. Viewed through the lens of the theory of allostatic load, the stress of discrimination may provide a plausible explanation. Chronic stress significantly affects glucose regulation.7 Stress releases large amounts of cytokines from adipose tissue and macrophages.6 Cytokines increase production of adrenocorticotropic hormone and cortisol, contributing to hypertension, obesity, and insulin resistance. A comparative descriptive design was employed to explore the effect of allostatic load as a measure of cumulative stress on abnormal glucose metabolism in a diverse sample of postmenopausal women. A convenience sample was recruited as a subsample of the Health Aging Research Initiative8 population in south Florida. Participants in this study had consented to be contacted for additional studies. Eligible Health Aging Research Initiative participants were contacted, the study requirements were explained, and questions were answered. For those consenting, an early morning home visit was scheduled with participants fasting. Data collection included completion of a demographic questionnaire and the Everyday Discrimination Scale,9 which was used to assess perceived interpersonal maltreatment during day-to-day experiences. Finally, a 30-mL venous blood sample was collected to measure blood glucose and allostatic load biomarkers. Building on previous research, an index of allostatic load was defined using nine biomarkers, including lipids, dehydroepiandrosterone sulfate, leptin, cytokines, and fibrinogen. An empirical risk threshold was identified for each biomarker. Any biomarker meeting or exceeding the defined threshold was assigned a score of 1. The index score was calculated by summing all at-risk biomarkers (maximum score 98). This approach has been used in prior studies and was predictive of cumulative stress.10 Twenty-seven women were recruited. One each was eliminated from analysis because of missing data and difficulty with venipuncture. A final analytical sample of 25 women completed the study with all of the required data. Analyses were performed using IBM SPSS Statistics 21 (IBM Corp., Armonk, NY). Descriptive statistics were used to evaluate demographic variables. A t-test was used to compare group means in terms of perception of discrimination, fasting blood glucose, and index of allostatic load. The mean age of the participants was 66.3 at the time of data collection. The sample was almost evenly split with regard to race, with 13 white and 12 black women. Fasting blood glucose levels differed significantly between racial groups (t = 1.26, P = .03), with levels being higher in black than white women. Black women perceived significantly more experiences of discrimination in their daily lives than did white women (t = 2.35, P = .03). Mean index of allostatic load scores also differed significantly between racial groups (t = 2.61, P = .02). Results are summarized in Table 1. These findings demonstrate a difference in perception of discrimination, allostatic load, and fasting blood glucose levels between black and white postmenopausal women. These results provide preliminary support for a relationship between postmenopausal blood glucose levels and stress related to everyday experiences of discrimination. Although these findings should be validated in further studies, these data indicate that allostasis may provide a fertile area of study to understand and address postmenopausal differences in insulin resistance and diabetes mellitus. Conflict of Interest: The author reports no competing interests or conflicts related to this letter. Funded by the Christine E. Lynn New Faculty Award from Florida Atlantic University. Author Contributions: Dr. Dormire is solely responsible for the preparation of the study concept, design, methods, analysis and interpretation of the data, and preparation of this paper. Sponsor's Role: None.