[1] Vanderbilt Univ, Sch Med, Med Ctr N, Sleep Disorders Div,Dept Neurol, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Sch Med, Dept Biostat, Nashville, TN 37232 USA
[3] Vanderbilt Univ, Vanderbilt Kennedy Ctr Human Dev, Nashville, TN 37232 USA
[4] Vanderbilt Univ, Sch Med, Med Scientist Training Program, Nashville, TN 37232 USA