1. Public Health Research Center, New York University Abu Dhabi, Abu Dhabi P.O. Box 129188, United Arab Emirates
2. College of Natural and Health Sciences, Zayed University, Abu Dhabi P.O. Box 19282, United Arab Emirates
3. College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai Health, Dubai P.O. Box 505055, United Arab Emirates
4. MRC Epidemiology Unit, University of Cambridge, Cambridge CB2 0SL, UK