1. From the Division of Epidemiology, Statistics, and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD (AJG, SLM, CZ, NJP, EY, and EFS); the Department of Social and Preventive Medicine, University at Buffalo, State University of New York, Buffalo, NY (JW-W and KMH); the Division of Biostatistics and Epidemiology, University of Massac