1Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
2Department of Health and Community Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3Department of Radiotherapy, Shahid Baheshti University of Medical Sciences, Tehran, Iran
4Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
5Digestive Disease Research Institute, Tehran University of Medical Sciences, Tehran, Iran
6Oncopathology Research Center, Iran University of Medical Sciences, Tehran, Iran
Copyright © 2018 The Korean Society for Preventive Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
CONFLICT OF INTEREST
The authors have no conflicts of interest associated with the material presented in this paper.