[1] Mayo Clin, Dept Anesthesiol, Rochester, MN 55905 USA
[2] Mayo Clin, Div Epidemiol, Rochester, MN 55905 USA
[3] Mayo Clin, Dept Psychiat & Psychol, Rochester, MN 55905 USA
[4] Mayo Clin, Mayo Med Sch, Coll Med, Rochester, MN 55905 USA
[5] Mayo Clin, Div Biomed Stat & Informat, Rochester, MN 55905 USA
[6] Childrens Hosp, Div Dev Med, Boston, MA 02115 USA