Eric B. Larson, MD, MPH, is a leading expert in the science of healthy aging. Since 1986, he has led a large, longitudinal research program focused on delaying and preventing Alzheimer's disease, other forms of dementia, and declines in memory and thinking. Called the Adult Changes in Thought (ACT) study, this program is the world's longest-running study of its kind and includes one of the largest research populations age 85 and older. ACT is a collaboration of Group Health (a Seattle-based health system) Kaiser Permanente, the University of Washington (UW), and the National Institute on Aging. Dr. Larson is also executive director of Kaiser Permanente Washington Health Research Institute (formerly Group Health Research Institute), a public-interest research center. In addition, he is a clinical professor of medicine at the UW School of Medicine and of health services at the UW School of Public Health. He also maintains an internal-medicine practice, providing primary care to his patients since 1975. Before joining Group Health in 2002, Dr. Larson served as medical director for the UW Medical Center and associate dean for clinical affairs at its medical school from 1989 to 2002. He is a member and past president of the Society of General Internal Medicine; member and former chair of the Board of Regents of the American College of Physicians; a master of the American College of Physicians; and an elected member of the National Academy of Medicine (formerly called the Institute of Medicine) of the National Academy of Sciences. Dr. Larson has published hundreds of research papers in peer-review medical journals-including the Journal of the American Medical Association, the New England Journal of Medicine, and Annals of Internal Medicine.