Erfan Ayubi1,2, Kamyar Mansori3, Salman Khazaei4. 1. Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran. 2. Department of Epidemiology & Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran. 3. Social Determinants of Health Research Center, Kurdistan University of Medical Sciences, Sanandaj. 4. Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.