[1] Heinrich Heine Univ Dusseldorf, Inst Med Sociol, Med Fac, Ctr Hlth & Soc, Dusseldorf, Germany
[2] Heinrich Heine Univ Dusseldorf, Univ Hosp Dusseldorf, Dusseldorf, Germany
[3] Fed Minist Hlth, Bonn, Germany
[4] Univ Cologne, Inst Med Sociol Hlth Serv Res & Rehabil Sci, Fac Human Sci, Cologne, Germany
[5] Univ Cologne, Fac Med, Cologne, Germany
[6] Univ Cologne, Fac Human Sci, Res Methods Dept, Cologne, Germany
[7] Heinrich Heine Univ, Inst Med Sociol, Med Fac, Ctr Hlth & Soc, Moorenstr 5, D-40225 Dusseldorf, Germany
[8] Heinrich Heine Univ, Univ Hosp Dusseldorf, Moorenstr 5, D-40225 Dusseldorf, Germany