Dr. Leff is Professor of Medicine at the Johns Hopkins University School of Medicine in the Division of Geriatric Medicine and Gerontology. He holds a joint appointment in the Department of Health Policy and Management at the Johns Hopkins University Bloomberg School of Public Health, and in the Johns Hopkins School of Nursing, Department of Community and Public Health.

He is the Director of the Center for Transformative Geriatric Research and is past Associate Director of the JHOME program.  His principal areas of health services research relate to the development, evaluation and dissemination of innovative models of health service delivery for older adults including Hospital at Home, Guided Care, home-based primary care, and others.  His research interests also include issues related to the care of people with multiple chronic conditions, the development of quality indicators for home-based medical care and quality improvement, guideline development and case-mix issues. He is the author of more than 200 peer-reviewed publications and book chapters. Dr. Leff has a strong interest in health policy and is a recent Health and Aging Policy Fellow and has served on multiple National Quality Forum and Centers for Medicare & Medicaid Services Technical Expert Panels. Dr. Leff cares for patients in the acute, ambulatory and home settings and is an award-winning teacher and mentor.

He currently serves as the Chair of the Geriatric Medicine Board of the American Board of Internal Medicine (ABIM) and is Chair-elect of the ABIM Council.  He is past -President and current board member of the American Academy of Home Care Physicians, and past-member of the Board of Regents of the American College of Physicians.  He serves on the editorial board of the Annals of Internal Medicine and is a Care Redesign Thought Leader for the New England Journal of Medicine Catalyst.

Dr. Leff received his medical degree from the New York University School of Medicine and completed residency in primary care internal medicine at the Johns Hopkins Bayview Medical Center, and a fellowship in geriatric medicine and gerontology at the Johns Hopkins University School of Medicine, in Baltimore.