1. Department of Epidemiology and Public Health, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
2. Centre for Health Services Research, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
3. Department of Statistics and Applied Probability, Faculty of Science, National University of Singapore, Singapore, Singapore
4. Medical Services, Ang Mo Kio Thye Hua Kwan Hospital, Singapore, Singapore
5. Medical Services, St Luke's Hospital, Singapore, Singapore
6. Department of Family Medicine, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
7. Lawson Health Research Institute, London, ON, Canada