1. From the University of California, San Francisco (M.C.F., A.S.G.); Clinical Epidemiology Unit, Massachusetts General Hospital, Boston (D.E.S., Y.C., L.E.H.); General Internal Medicine and Clinical Epidemiology Unit, Boston University School of Medicine, Boston, Mass (E.M.H.); and Division of Research, Kaiser Permanente of Northern California, Oakland (N.G.J., A.S.G.).