1 School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada: Centre for Health Evaluation and Outcome Sciences, St Paul's Hospital, Vancouver, BC, Canada: Centre for Clinical Epidemiology and Evaluation, Vancouver Coastal Research Institute, Vancouver, BC, Canada.
2 Centre for Health Evaluation and Outcome Sciences, St Paul's Hospital, Vancouver, BC, Canada: Department of Medicine and Sleep Disorders Program, University of British Columbia, Vancouver, BC, Canada.