Siamak Sabour1,2. 1. Safety Promotion and Injury Prevention Research Center, Department of Clinical Epidemiology, School of Health, Shahid Beheshti University of Medical Sciences, Tehran, 198353-5511, Islamic Republic of Iran. s.sabour@sbmu.ac.ir. 2. Department of Clinical Epidemiology, Shahid Beheshti University of Medical Sciences, Tehran, Islamic Republic of Iran. s.sabour@sbmu.ac.ir.