1. Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
2. Department of Biostatistics and Epidemiology, Sabzevar University of Medical Sciences, Sabzevar, Iran
3. Department of Internal Medicine, School of Medicine, Sabzevar University of Medical Sciences, Sabzevar, Iran
4. School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran