Reza Pakzad1, Saeid Safiri2,3. 1. Department of Epidemiology, Faculty of Health, Ilam University of Medical Sciences, Ilam, Iran. 2. Department of Public Health, Managerial Epidemiology Research Center, School of Nursing and Midwifery, Maragheh University of Medical Sciences, Maragheh, Iran. saeidsafiri@gmail.com. 3. Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. saeidsafiri@gmail.com.