Dissertation Title： "Variation in Quality and Costs of Care across Physicians and Its Determinants"This dissertation evaluates one of the key determinants of health care quality and costs – practice patterns of physicians. A large body of literature has demonstrated substantial geographic variation in health care utilization without concomitant improvement in patient outcomes in higher spending regions. While informative, however, this literature did not investigate the variation due to individual physician behaviors, despite the central role of physicians as key decision makers in health care. This dissertation attempts to shed light on these questions by analyzing the productivity of health care spending at the physician level.

Chapter 1 investigates the proportion of service use variation that can be explained by variation in individual physician practice patterns, and examines the impact of that variation on patient outcomes. Using the data on Medicare beneficiaries hospitalized with medical conditions, I found that variation in spending across physicians is larger than variation across hospitals. As for evaluating the impact of between-physician variation in spending on patient outcomes, I exploited a specific natural experiment of physicians who specialize in hospital-based care – hospitalist physicians. Patients are plausibly randomized within a hospital based on hospitalists' specific work schedule. I found that patients treated by higher-spending hospitalists have lower mortality than those cared for by lower-spending hospitalists, with no difference in patients’ readmission rates. The implication of this study is that efforts to improve value in health care by constraining health care spending (particularly among physicians) may have different effects than predicted from analyses of health care productivity based on the regional level.

Chapter 2 begins my evaluation of the upstream determinants of variation in quality of care across physicians with a special focus on physician experience. Physicians with longer experience may accumulate, or conversely exhibit obsolescence of, knowledge and skills. The association between physicians’ years of experience and patient outcomes is, however, poorly understood. Using the nationally representative data on Medicare beneficiaries, I found that, despite similar patient characteristics, physicians with more years in practice have higher patient mortality than physicians with fewer, except for physicians with high patient volume. These findings suggest that at least some clinical outcomes of physicians may deteriorate over a career and that efforts to improve continuing medical education may be more important than previously realized.

Chapter 3 assesses another upstream determinant of between-physician variation in quality of care –physician sex. Studies have found differences in practice patterns between male and female physicians, with female physicians more likely to adhere to clinical guidelines and evidence-based practice. However, whether patient outcomes differ between male and female physicians is largely unknown. I found that female physicians had lower 30-day patient mortality and readmission rates compared to male physicians, within same hospital. Although the exact mechanism underlying these differences remains unclear, understanding why these differences in care quality exist, and what we might do to alleviate them, is critical to ensuring that all patients get high quality care.