[1] Univ Cologne, Fac Med, Cologne, Germany
[2] Univ Cologne, Univ Hosp Cologne, Polyclin Operat Dent & Periodontol, Cologne, Germany
[3] Univ Cologne, Fac Human Sci, Grad Sch GROW Gerontol Res Well being, Cologne, Germany
[4] Univ Cologne, Fac Med, Grad Sch GROW Gerontol Res Well being, Cologne, Germany
[5] Univ Hosp Cologne, Inst Hlth Econ & Clin Epidemiol, Cologne, Germany
[6] Uniklin Koln, Poliklin Zahnerhaltung & Parodontol, Kerpener Str 32, D-50931 Cologne, Germany