[1] Framingham Heart Dis Epidemiol Study, Framingham, MA 01702 USA
[2] Boston Univ, Sch Med, Cardiol Sect, Boston, MA 02118 USA
[3] Boston Univ, Sch Med, Dept Epidemiol & Prevent Med, Boston, MA 02118 USA
[4] Massachusetts Gen Hosp, Div Cardiol, Boston, MA 02114 USA
[5] Harvard Univ, Sch Med, Boston, MA USA
[6] NHLBI, Bethesda, MD 20892 USA