1. Department of Medicine, Landspitali University Hospital of Iceland, Reykjavik, Iceland
2. The Icelandic Prescription Medicines Registers, Director of Health, Reykjavik, Iceland
3. Department of Rheumatology, Landspitali University Hospital of Iceland, Reykjavik, Iceland
4. Faculty of Medicine, University of Iceland, Reykjavik, Iceland
5. Centre for Rheumatology Research, Landspitali University Hospital of Iceland, Reykjavik, Iceland