[1] Univ N Carolina, Sch Med, Dept Med, Div Cardiol, Chapel Hill, NC 27599 USA
[2] Univ N Carolina, Sch Med, Dept Epidemiol, Chapel Hill, NC 27599 USA
[3] Univ N Carolina, Sch Publ Hlth, Chapel Hill, NC 27599 USA
[4] Univ Minnesota, EPICARE Ctr, St Paul, MN USA
[5] Univ Minnesota, Sch Publ Hlth, Div Epidemiol, St Paul, MN USA