[1] Univ Botswana, Fac Med, Gaborone, Botswana
[2] Princess Marina Hosp, Gaborone, Botswana
[3] Gaborone Private Hosp, Gaborone, Botswana
[4] Bokamoso Private Hosp, Gaborone, Botswana
[5] Univ Sheffield, Ctr Metab Bone Dis, Sheffield, S Yorkshire, England
[6] Australian Catholic Univ, Mary McKillop Inst Hlth Res, Melbourne, Vic, Australia
[7] Univ Southampton, MRC Lifecourse Epidemiol Unit, Southampton, Hants, England
[8] Univ Sheffield, Dept Oncol & Metab, Mellanby Ctr Musculoskeletal Res, Sheffield, S Yorkshire, England
[9] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Epidemiol, Pittsburgh, PA 15260 USA