[1] Vet Adm Med Ctr, Ctr Chron Dis Outcomes Res, Minneapolis, MN 55417 USA
[2] Univ Minnesota, Sch Publ Hlth, Div Epidemiol, Minneapolis, MN 55455 USA
[3] Univ Calif Los Angeles, David Geffen Sch Med, Cedars Sinai Med Ctr, Dept Med,Burns & Allen Res Inst, Los Angeles, CA USA
[4] Univ Texas, Hlth Sci Ctr, Inst Mol Med, Houston, TX USA
[5] Wake Forest Univ, Dept Radiol, Winston Salem, NC 27109 USA
[6] Kaiser Permanente Med Care Program, Div Res, Oakland, CA 94611 USA