[1] Univ Lucerne, Dept Hlth Sci & Med, CH-6002 Luzern, Switzerland
[2] Univ Geneva, Inst Global Hlth, CH-1211 Geneva, Switzerland
[3] Univ Hosp Basel, CLEAR Methods Ctr, Dept Clin Res, Div Clin Epidemiol, CH-4031 Basel, Switzerland
[4] Univ Basel, CH-4031 Basel, Switzerland
[5] Univ Hosp Basel, Dept Orthopaed Surg & Traumatol, CH-4031 Basel, Switzerland
[6] Loughborough Univ, Ctr Informat Management, Sch Business & Econ, Loughborough LE11 3TU, England
[7] Univ Washington, Dept Epidemiol, Seattle, WA 98195 USA
[8] Harvard Med Sch, Dept Global Hlth & Social Med, Boston, MA 02115 USA
[9] Univ Svizzera Italiana, Inst Publ Hlth, CH-6900 Lugano, Switzerland
[10] Univ Zurich, Epidemiol Biostat & Prevent Inst, CH-8001 Zurich, Switzerland