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Advisory Committee Chair

Erica R Pryor

Advisory Committee Members

Susan Appel

Mary A Hess

Fernando Ovalle

Marti Rice

Document Type

Dissertation

Date of Award

2016

Degree Name by School

Doctor of Philosophy (PhD) School of Nursing

Abstract

Introduction African-Americans experience more years of life lost as a result of complications from type 2 diabetes mellitus (T2DM) than any other racial or ethnic group. Evidence suggests that serum 25(OH)D (serum vitamin D), generally low in African-Americans, may play a role in glucose control. In addition, elevated levels of chronic low-grade inflammation, measured by C-reactive protein (CRP), may also relate to glucose control. The purposes of this study were to determine whether serum 25(OH)D and CRP are independent predictors of glucose control in adult African-Americans with T2DM, after controlling for other factors associated with glucose control, and to examine whether there are gender differences in these relationships. Methods A secondary data analysis was performed on de-identified clinical data obtained from electronic medical records from a university-affiliated health system in a large southeastern city. Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) were the outcome measures of glucose control. Statistical analyses included bivariate correlations, independent samples t-tests, and hierarchical multiple linear regression.   Results In the CRP analysis sample dataset (n=260), no significant correlations were found between CRP and FPG (r=.115, p=.31) or between CRP and HbA1c (r=.21, p=.08). Significant inverse correlations were found between serum 25(OH)D and FPG (r=-.20, p=.003) and with HbA1C (r=-.22, p< .001) in the serum vitamin D analysis dataset (n=574). In separate regression models for each outcome, after controlling for selected covariates, serum 25(OH)D explained 2% of the variability in FPG (R2change=.02, p=.035) but only 1.1% of the variability in HbA1c (R2change =.011, p=.051). Gender was not a moderator of the relationship between serum vitamin D and either measure of glucose control. Males had lower mean vitamin D levels than females (t=-2.98, df=274.1, p=.003). Conclusions Serum vitamin D was an independent predictor for FPG but not HbA1c. There was no significant association between CRP and the two measures of glucose control. This study is one of the first to examine the relationships between serum vitamin D and CRP and measures of glucose control in African-American adults with T2DM. Additional prospective studies of these relationships are recommended. Keywords: type 2 diabetes, glucose control, vitamin D, C-reactive protein, African-Americans

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