Date of Award

Spring 5-9-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Public Health

First Advisor

Ike S. Okosun, MS, MPH, PhD

Second Advisor

Douglas W. Roblin, PhD

Third Advisor

Michael Goodman, MD, MPH

Abstract

The role of stress (both psychosocial and oxidative) in the pathophysiology of several chronic diseases has been documented and has become a focus for chronic disease prevention and management. Although, psychosocial stress (PS) and oxidative stress (OS) have different mechanisms through which they impact health, they both cause physiological imbalance which might subsequently lead to a disease state. Laboratory and observational studies have linked both stresses to the pathophysiology of diabetes mellitus (DM) and hypertension. However, findings from previous studies have not been entirely consistent and results have varied based on the study population and the stress-measurement tool used. Given the gaps in the literature, three studies were conducted to examine: (1) the relationship between PS and glycemic control; (2) the association between PS and estimated glomerular filtration rate (eGFR); and (3) the association between OS and hypertension among adults.

In the first two studies, a longitudinal data from Kaiser Permanente Georgia (KPGA) survey on Health and Healthy Behaviors linked to patients’ laboratory and pharmacy records was used. In the third study a cross-sectional data from Study on Race, Stress and Hypertension was used.

The first study examined the association between baseline measure of work-related PS and glycemic control using both cross-sectional and longitudinal designs. None of the four PS sub-scales or the overall PS measure at the work environment was significantly associated with glycemic control at either study baseline or over time. The second study examined the association between general measures of PS and changes in estimated glomerular filtration rate (eGFR) over time in a structural equation model framework. No significant direct association was observed between general PS measure and eGFR decline. However, age, race, mean arterial pressure and insulin use were found to be associated with eGFR decline. The third study examined the association between hypertension and: 1) four markers of OS (F2-Isoprostanes, Fluorescent oxidative products, copy number of mitochondrial DNA and Gamma-tocopherol); and 2) plasma nutrient based oxidative balance score (OBS). The OBS was inversely associated with hypertension, but none of the OS markers was significantly associated with hypertension after adjusting for study covariates.

The current work highlights some of methodological issues in the assessment of PS to examine their relationship with DM control and complications. The study also highlights the need for more future studies to be conducted to confirm the association between OBS and hypertension, preferably longitudinal studies. If future studies confirm this finding, then the mechanisms by which OBS may influence risk of hypertension would need to be explored further.

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