Browsing Theses and Dissertations by Subjects
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Impact of Genetic Predisposition and Environmental Stress on Measures of Preclinical Essential HypertensionThe main objective of this project was to determine the impact of genetic risk and chronic environmental stress on measures of preclinical essential hypertension (EH) (e.g., exaggerated cardiovascular reactivity, increased resting hemodynamics and increased left ventricular mass [LVM]). A secondary objective was to evaluate the moderating and interactive effects of ethnicity, gender, body mass index [BMI] and anger expression on EH risk indices. Two genes with relevance for blood pressure (BP) control (e.g., beta-2 adrenergic receptor [ADRB2] gene and serotonin transporter [5-HTT] gene) were used to define genetic risk. Chronic environmental stress was assessed by socioeconomic status (SES) and subjective social status (SSS). The project consisted of three sequential studies on a large, multiethnic cohort of young adults (N>500). The first two studies were cross-sectional and based on the analysis of cardiovascular reactivity, resting hemodynamics and LVM data collected at a single visit. The third study was longitudinal and involved the tracking of BP and LVM over a 15-year span from childhood to early adulthood. In the first study, ADRB2 haplotype significantly interacted with anger suppression in African Americans such that high anger suppressing carriers had the highest resting SBP (p<.05) and TPR reactivity to a cold pressor task (p<.01). In European Americans, ADRB2 haplotype significantly interacted with BMI to predict resting hemodynamics, such that carriers who were high in BMI showed the highest SBP (p<.05). In the second study, a significant interaction between the 5-HTT promoter region polymorphism (5-HTTLPR) and social status was found for cardiovascular reactivity, such that S allele homozygotes who were low in SES and high in SSS exhibited the greatest BP and TPR reactivity to the video game stressor (p-values<.05). No significant interaction was found between 5- HTTLPR and social status in the longitudinal study, however a significant 5- HTTLPR by BMI interaction was determined for LVM, such that obese LL homozygotes had the greatest LVM over time (p<.001). Results from this project expand what is currently known with regard to EH etiology and carry implications for the prevention of EH through the early consideration of genetic, environmental and demographic risk factors.