1. Department of Biostatistics; Erasmus MC; PO Box 2040 Rotterdam 3000 CA The Netherlands
2. Department of Public Health; Erasmus MC; Rotterdam The Netherlands
3. Department of General Practice; VU Medical Centre; Amsterdam The Netherlands
4. EMGO Institute for Health and Care Research; VU Medical Centre; Amsterdam The Netherlands
5. Department of General Practice and Elderly Care Medicine; VU Medical Center; Amsterdam The Netherlands