1. Department of Public Health and Nursing, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology , Trondheim , Norway
2. Tabriz Health Services Management Research Center, Tabriz University of Medical Sciences , Tabriz , Iran
3. Center for Oral Health Services and Research, Mid-Norway (TkMidt) , Trondheim , Norway
4. Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London , London , UK
5. Department of Nutrition, Oslo New University College , Oslo , Norway
6. Department of Research, Cancer Registry of Norway , Oslo , Norway