Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, 21205, USA. Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, Maryland, 21205, USA. Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, 02111, USA. Metabolon, Research Triangle Park, Morrisville, North Carolina, 27560, USA. Division of General Internal Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, 21205, USA.