1. Department of Cardiology, Akershus University Hospital , Lørenskog , Norway
2. Institute of Clinical Medicine, University of Oslo , Oslo , Norway
3. Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital , Boston, MA , USA
4. Division of Sleep Medicine, Harvard Medical School , Boston, MA , USA
5. Inova Heart and Vascular Institute, Inova Fairfax Medical Campus , Falls Church, VA , USA
6. Division of Cardiology, Department of Medicine, Johns Hopkins Hospital and School of Medicine , Baltimore, MD , USA