Causes and Consequences of Healthcare Efficiency: Overview U.S. health care spending is at an all-time high, yet life expectancy is stagnant, raising concerns that projected spending growth won’t lead to commensurate health gains. This is a problem especially pertinent to older adults, with a high burden of illness and intense use of health care. In this P01 renewal application, we propose to continue our long-standing work identifying efficiency and inefficiency in U.S. health care by applying sophisticated empirical methods to more than 1 billion person-years of health data. We address 3 topics integral to health care delivery efficiency: First, our exploration of challenges in clinical decision making is expected to identify systematic underuse of effective care and overuse of ineffective care, and provide evidence where clinical trials are lacking. Second, we will examine the role of the health care delivery environment – how do patient-sharing networks, payment models, and regulations affect patient health? Third, through our multi-payer data, we seek to understand the limitations of policy analysis arising from a focus on just Medicare or private (commercial) data. For example, we seek to measure how high commercial payment rates affect access for Medicare or Medicaid enrollees. All projects aim to measure and improve quality of care for older, vulnerable populations, including people with Alzheimer’s Disease and related dementia (ADRD). We propose 3 cores and 5 projects. Core A provides administrative support, Core B coordinates data; and Core C (Methods) develops new approaches to network analysis used in all 5 projects. In Project 1, “Correlates and Consequences of Making an Alzheimer’s Disease Clinical Diagnosis,” we use the 100% Medicare files and clinically rich survey data to document variation in ADRD diagnosis, and test whether early diagnosis is, on net, beneficial to patients. Project 2, “The Causes and Consequences of Risky Prescribing,” uses Medicare Part D prescription data to study adverse outcomes associated with individual drugs and drug combinations including opioid analgesics, benzodiazepines, and sedative hypnotics. We consider forces influencing high-risk prescribing, such as shared-patient networks and legal restrictions. Project 3, “Identifying Efficient Health Care Providers: Evidence from Hospital Closures and Registry Data” uses peripheral vascular disease (PAD) registry data, and claims data, to estimate the relative expertise of community hospitals. This project will validate methods with natural experiments (hospital closing) and an ongoing randomized trial. Project 4, “Causes and Consequences of Variation in Public and Private Payment Rates,” hypothesizes that high commercial reimbursement rates can negatively affect access to care for Medicare and Medicaid patients. Finally, Project 5, “Physician Cognition, Inpatient Advance-Care Planning, and Outcomes for Seriously Ill Older Adults,” uses a combination of o...