[1] Univ Birmingham, Inst Biomed Res, Sch Clin & Expt Med, Birmingham B15 2TT, W Midlands, England
[2] Univ Hosp Birmingham, Dept Diabet, Birmingham, W Midlands, England
[3] Univ Birmingham, Sch Hlth & Populat Sci, Birmingham B15 2TT, W Midlands, England
[4] NHS Fdn Trust, Dudley Grp Hosp, Russells Hall Hosp, Diabet & Endocrine Ctr, Dudley, W Midlands, England
[5] Univ Bristol, Sch Clin Sci, Bristol, Avon, England