Karen Smith Successfully Defends Dissertation

Karen Smith, doctoral student in Health Policy concentrating in Decision Science, successfully defended her thesis, “Essays on Decision Analytic Modeling for Hypertension and Frailty.” Her dissertation committee was chaired by CHDS faculty Ankur Pandya and included Nicolas Menzies and David Cutler.

Smith used decision analytic modeling to evaluate two clinical conditions prevalent in the United States: hypertension and frailty. In her first chapter, she studied the value of targeting systolic blood pressure (SBP) targets in settings with different SBP measurement error. Clinical trials have found that intensive SBP targets (i.e., targeting a SBP <120 mm Hg) are effective at reducing cardiovascular event rates for patients with high cardiovascular disease risk. However, major clinical guidelines recommend higher targets of <130 mm Hg and <140 mm Hg, due to concerns that SBP measurement error in routine practice combined with an intensive target would lead to overtreatment. To evaluate the value of intensive targets in routine practice, Smith developed a disease simulation model of hypertension that simulates different levels of SBP measurement error. She found that an intensive <120 target would be cost-effective in settings with average or better levels of error. However, there is greater uncertainty with high levels of error, and a <130 mm Hg target may be cost-effective. This work suggests that recommendations for SBP targets for patients with high cardiovascular risk should consider SBP measurement accuracy and that an intensive target may be cost-effective in many clinical settings.

In her second chapter, Smith evaluated methods frequently used in disease simulation models to simulate the effect of SBP changes. Trials of SBP-lowering interventions frequently use SBP change as the primary outcome. As a result, cost-effectiveness analyses of these interventions must make assumptions about how SBP changes will affect long-term health outcomes, such as cardiovascular events and medication-related serious adverse events. She evaluated commonly used methods for projecting cardiovascular event rates based on SBP change and then estimated rates of intervention-related serious adverse events as a function of SBP and standardized antihypertensive doses using an instrumental variables analysis. This work can be used to inform and strengthen the validity of future economic evaluations of SBP-lowering interventions.

In her third chapter, Smith studied the health and financial burden of frailty and fall-related injuries among people with HIV. People with HIV experience age-related comorbidities, such as frailty and falls, at higher rates than people of the same age without HIV. In this work, she developed a disease simulation model of frailty and fall-related injuries among people with HIV and used this model to estimate the life years lost, quality-adjusted life-years (QALYs) lost, and costs attributable to frailty and falls. Describing these costs and health losses may motivate future work to inform decisions about how to provide high value care to prevent and treat frailty and fall-related injuries.