1From the Charles A. Dana Research Institute and the Harvard-Thorndike Laboratory of the Department of Medicine, Cardiovascular Division, Beth Israel Hospital and Harvard Medical School, Boston, Massachusetts USA
2The Framingham Heart Study of the National Heart, Lung, and Blood Institute, Framingham, Massachusetts USA
3Division of Epidemiology and Clinical Applications, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
4Department of Epidemiology and Preventive Medicine, University Hospital and Boston University School of Medicine, Boston, Massachusetts USA