[1] Robert Bosch Krankenhaus, Dept Clin Gerontol, Auerbachstr 110, D-70376 Stuttgart, Germany
[2] Univ Exeter, Coll Med & Hlth, St Lukes Campus, Exeter EX12LU, Devon, England
[3] Univ Med Ctr Hamburg Eppendorf, Dept Hlth Econ & Hlth Serv Res, Hamburg, Germany
[4] Ulm Univ, Inst Epidemiol & Med Biometry, Helmholtzstr 22, D-89081 Ulm, Germany