Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.|Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.|Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.|Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.|Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.|Department of Epidemiology and Public Health, National University of Singapore, 16 Medical Drive, Singapore.