[1] Univ York, Dept Hlth Sci, York, N Yorkshire, England
[2] Univ Oxford, Ctr Stat Med, Oxford, England
[3] Oregon Coll Oriental Med, Dept Res, Portland, OR USA
[4] Sichuan Univ, West China Hosp, Chinese Evidence Based Med Ctr, Chinese Cochrane Ctr, Chengdu, Sichuan, Peoples R China
[5] Univ Exeter, Peninsula Med Sch, Primary Care Res, Exeter, Devon, England
[6] Univ Plymouth, Plymouth, Devon, England
[7] Univ Ottawa, Ottawa Methods Ctr, Ottawa Hosp Res Inst, Ottawa, ON, Canada
[8] Univ Ottawa, Dept Epidemiol & Community Med, Ottawa, ON, Canada