1. From the Stanford Prevention Research Center, Department of Medicine and Department of Health Research and Policy, Stanford University School of Medicine, and Department of Statistics, Stanford University School of Humanities and Sciences, Stanford, CA (J.P.A.I.), Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece and Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, UK (I.T.).