Department of Aging and Geriatric Research, Institute on Aging, University of Florida, Gainesville, Florida, USA. Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, USA. Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, Maryland, USA. Division of Endocrinology, Diabetes and Metabolism, College of Medicine, University of Florida, Gainesville, Florida, USA. Department of Health Services Research, Management and Policy, University of Florida, Gainesville, Florida, USA. Department of Community Health and Family Medicine, University of Florida, Gainesville, Florida, USA. Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.