[1] Vanderbilt Univ, Med Ctr N, Dept Neurol, Sleep Disorders Div,Sch Med, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Sch Med, Dept Biostat, Nashville, TN 37232 USA
[3] Cleveland Clin, Dept Neurol, Cleveland, OH 44106 USA
[4] Univ N Carolina, Dept Neurol, Chapel Hill, NC 27515 USA
[5] Univ Michigan, Med Ctr, Dept Neurol, Ann Arbor, MI 48109 USA
[6] Univ Michigan, Michigan Inst Clin & Hlth Res, Ann Arbor, MI 48109 USA