1 From the Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA.
2 Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC.
3 Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC.
4 Department of Biostatistics, Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
5 Department of Epidemiology, Erasmus University Medical Center, Rotterdam, the Netherlands.