Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Bioinformatics, Biostatistics, and Epidemiology

College

College of Graduate Studies

First Advisor

Daniel T. Lackland

Second Advisor

Robert J. Adams

Third Advisor

David L. Bachman

Fourth Advisor

Brent M. Egan

Fifth Advisor

Andrew B. Lawson

Sixth Advisor

Joyce S. Nicholas

Abstract

Introduction: An inherent risk from an incident stroke is recurrence. The most effective method to reduce stroke risk is to reduce the incidence of hypertension. Thus, antihypertension therapy has become imperative in the prevention of primary and recurrent stroke. In this dissertation we examine the confounding effects of race and age on recurrent stroke risk and the consistency of secondary prevention treatment regimens. Methods: One-year recurrent stroke risk was determined in relation to race, age, gender, and comorbid hypertension and diabetes by mixed effects regression and Kaplan-Meier survival analyses among hospitalized patients in South Carolina. A subset of patients were used to estimate race- and age-specific rate ratios for stroke incidence and recurrence based on symptomatic and asymptomatic discharge diagnoses modifier code selection. A hospital-based subset of stroke survivors was surveyed via structured telephone interviews to determine predictors of antihypertensive regimen persistence from hospital discharge to one-year by logistic regression analyses. Results: One-year recurrent stroke was identified in 11.3% of hospitalized patients with highest rates among African Americans, patients age 45-64 years, and patients with diabetes. The magnitude of the racial disparity rate ratios for both stroke incidence and recurrence was significantly higher when only symptomatic stroke diagnoses were considered. Advanced age, comorbidity, uncontrolled blood pressure (≥140/90 mmHg), premorbid antihypertensive therapy, and receipt of antilipidemics or antithrombotics were significantly associated with receipt of antihypertensive therapy at discharge. Within one-year post stroke hospitalization, 87% of the treated patients remained on some type of antihypertensive therapy, while only 39% were persistent on the same regimens. African Americans and comorbid conditions were inversely associated with persistence on antihypertension therapy. Conclusions: The results of this study identified one-year recurrent stroke impacting one in ten stroke survivors. Further, younger age, African American race, and prevalent diabetes significantly increases recurrent stroke risk and emerge as factors to consider in risk-reduction strategies. Persistence on antihypertensive regimen one-year post discharge was significantly lower for certain medication classes, African Americans, and patients with high comorbidities. Recurrent stroke risk for these high risk groups could be reduced by understanding the effects of race and comorbid conditions on medication persistence.

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