[1] Boston Univ, Sch Med, Div Gastroenterol, Boston Med Ctr, Boston, MA 02118 USA
[2] NHLBI, Framingham Heart Study, Framingham, MA USA
[3] Merck Res Labs, Kenilworth, NJ USA
[4] Boston Univ, Dept Math & Stat, Boston, MA 02215 USA
[5] Harvard Univ, Sch Med, Dept Radiol, Massachusetts Gen Hosp, Boston, MA 02115 USA
[6] Harvard Univ, Brigham & Womens Hosp, Sch Med, Div Endocrinol Hypertens & Metab, Boston, MA 02115 USA