[1] Robert Bosch Krankenhaus, Dept Clin Gerontol, D-70376 Stuttgart, Germany
[2] Univ Ulm, Inst Epidemiol & Med Biometrie, D-89069 Ulm, Germany
[3] Univ Maryland, Sch Med, Dept Epidemiol & Publ Hlth, Baltimore, MD 21201 USA
[4] Univ Med Ctr Hamburg Eppendorf, Inst Hlth Econ & Hlth Serv Res, Hamburg, Germany