1. From the Division of Epidemiology and Clinical Applications, National Heart, Lung, and Blood Institute, Bethesda, Maryland, Cardiovascular Health Branch, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, and Department of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem and Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, North Carolina