1. Department of Family Medicine and Internal Diseases, Northern State Medical University, 163069 Arkhangelsk, Russia
2. Biorhythmology Laboratory of the Institute of Environmental Physiology, N. Laverov Federal Center for Integrated Arctic Research of the Ural Branch of the Russian Academy of Sciences, 163001 Arkhangelsk, Russia
3. Department of Community Medicine, UiT The Arctic University of Norway, N-9037 Tromsø, Norway