[1] Univ Cologne, Fac Med, Gleueler Str 176-178, Cologne, Germany
[2] Univ Hosp Cologne, Inst Nursing Sci, Gleueler Str 176-178, Cologne, Germany
[3] Univ Cologne, Fac Med, Eupener Str 129, Cologne, Germany
[4] Univ Hosp Cologne, Chair Hlth Serv Res, Inst Med Sociol Hlth Serv Res & Rehabil Sci, Eupener Str 129, Cologne, Germany
[5] Univ Cologne, Fac Med, Robert Koch Str 10, Cologne, Germany
[6] Univ Hosp Cologne, Inst Med Stat & Computat Biol, Robert Koch Str 10, Cologne, Germany
[7] Univ Hosp Cologne, Inst Hlth Econ & Clin Epidemiol, Gleueler Str 176-178, Cologne, Germany