PhD Oral Exam - Amanda Rossi, Individualized Program

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Hypertension is the leading risk factor for the development of cardiovascular disease (CVD). Physical activity (PA) is beneficial for preventing hypertension and decreases risk of mortality and CVD. The purpose of this thesis was to study the relationships between PA, blood pressure (BP), and how they act to impact mortality and CVD development.

A systematic review examined the impact of PA on mortality in patients with high BP. Six articles evaluating over 90,000 participants were identified. C and all-cause mortality were shown to be inversely related to PA in all studies. Individuals with high BP who participated in any level of PA had a reduced risk of CVD mortality, and greater than two-fold increased risk of mortality was noted for inactive individuals.

The second study specifically examined the main and interaction effects of different levels of PA and BP on both fatal and non-fatal CVD events, and mortality in the Scottish Health Survey. We found a significant interaction effect between PA and BP on CVD such that doing any level of activity for the BP groups <160 mmHg reduced risk of CVD; in those with systolic BP ≥160 mmHg, there was no change in risk.

The third study evaluated the causal relationships between PA, BP, and mortality and Major Adverse Cardiovascular Events (MACE) using the Honolulu Heart Program. Advanced statistical models (i.e., Marginal structural models) were used to estimate the separate causal relationships of PA and BP on mortality/MACE, and the causal relationship of PA on BP. Being active was associated with reduced risk of mortality and MACE. BP was shown to have a dose-dependent relationship with all-cause mortality and MACE (increased BP increased risk of events). Active participants showed a reduced BP (~2.5 mmHg). Being physically active is associated with better outcomes and that BP may be a mediator of this relationship.

The findings from this thesis suggest a causal relationship between greater PA and lower BP, and that high PA acts with low BP in reducing the risk of mortality and cardiovascular events. This outcome supports engagement in physical activity for longevity and maintenance of healthy blood pressure.