1. Department of Epidemiology, Faculty of Public HealthShiraz University of Medical Sciences Shiraz Iran
2. Behbahan Faculty of Medical Sciences Behbahan Iran
3. Research Center for Environmental Determinants of Health (RCEDH)School of Health, Kermanshah University of Medical Sciences Kermanshah Iran
4. Colorectal Research CenterFaghihi Hospital, Shiraz University of Medical Sciences Shiraz Iran
5. Center for Health Related Social and Behavioral Sciences ResearchShahroud University of Medical Sciences Shahroud Iran
6. Oslo Centre for Biostatistics and Epidemiology, Department of BiostatisticsInstitute of Basic Medical Sciences, University of Oslo Oslo Norway