1. Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808-4124, USA.
2. Department of Community Health and Epidemiology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada.
3. Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
4. Faculty of Health Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
5. Department of Community Health and Epidemiology, Dalhousie University, Halifax, NS B3H 1V7, Canada.
6. Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC H3A 1A2, Canada.