1. Department of Clinical Epidemiology; Aarhus University Hospital; Aarhus N Denmark
2. Center for Observational Research; Amgen Inc; Cambridge MA USA
3. Department of Internal Medicine; Østfold Hospital Trust; Fredrikstad Norway
4. Department of Medicine, Solna; Centre for Pharmacoepidemiology; Karolinska Institutet; Stockholm Sweden
5. Center for Observational Research; Amgen Inc; South San Francisco CA USA