1. Department of Internal Medicine, Isala Clinics, Zwolle, The Netherlands
2. Department of Internal Medicine, University Medical Center Groningen, Groningen, The Netherlands
3. Department of Diabetes Centre, Isala Clinics and Langerhans Medical Research Group, Zwolle, The Netherlands
4. Department of General Practice, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands
5. Department of Internal Medicine and University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
6. Department of Internal Medicine and Diabetes Centre, Isala Clinics, Zwolle, The Netherlands and Department of Internal Medicine, University Medical Center Groningen, Groningen, The Netherlands