1. Respiratory Epidemiology Unit, Joint Departments of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada; Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, USA
2. Respiratory Epidemiology Unit, Joint Departments of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal,Canada; Respiratory Division, Montreal Chest Institute, McGill University Health Center, Montreal, Canada