[1] Robert Bosch Krankenhaus Stuttgart, D-70376 Stuttgart, Germany
[2] Univ Ulm, Inst Epidemiol & Med Biometry, D-89081 Ulm, Germany
[3] Univ Med Ctr Hamburg Eppendorf, Hamburg Ctr Hlth Econ, Dept Hlth Econ & Hlth Serv Res, D-20246 Hamburg, Germany
[4] Univ Zurich Hosp, Neurol Clin, CH-8091 Zurich, Switzerland
[5] Univ Ulm, Inst Stat, D-89081 Ulm, Germany