1. Department of Molecular and Clinical Medicine, Institution of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
2. Sleep Medicine Unit, Skaraborg Hospital, Skövde, Sweden
3. Division of Periodontology, Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden
4. Centre for Applied Biostatistics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden