[1] Mayo Clin, Coll Med, Div Gastroenterol & Hepatol, Rochester, MN 55905 USA
[2] Mayo Clin, Coll Med, Div Primary Care Internal Med, Rochester, MN 55905 USA
[3] Mayo Clin, Coll Med, Div Biostat, Rochester, MN 55905 USA
[4] Mayo Clin, Coll Med, Div Epidemiol, Rochester, MN 55905 USA
[5] Mayo Clin, Coll Med, Dept Otolaryngol, Rochester, MN 55905 USA