[1] Johns Hopkins Univ, Sch Med, Baltimore, MD 21205 USA
[2] Vanderbilt Univ, Med Ctr, Dept Med, Ctr Hlth Serv Res,Div Gen Internal Med & Publ Hlt, Nashville, TN USA
[3] Vanderbilt Univ, Med Ctr, Ctr Diabet Res & Training, Nashville, TN USA
[4] VA Tennessee Valley Healthcare Syst, Nashville, TN USA
[5] Vanderbilt Univ, Med Ctr, Dept Biostat, Nashville, TN USA
[6] Univ Michigan, Sch Med, Ann Arbor, MI USA