1. Division of Epidemiology and Community Health (N.Z., J.S.P., M.P.), School of Public Health, University of Minnesota, Minneapolis, Minnesota 55454;
2. Department of Medicine (C.M.B., R.C.H.), Baylor College of Medicine, Houston, Texas 77030;
3. Department of Biostatistics (D.C.) School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599;
4. Department of Epidemiology (B.B.D., M.I.S.), School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599;
5. Graduate Studies Program in Epidemiology (B.B.D., M.I.S.), School of Medicine, Federal University of Rio Grande do Sul, 90470-280 Porto Alegre, Brazil