1. Department of Epidemiology (J.A.C., J.M.Z.), University of Pittsburgh, Pittsburgh, Pennsylvania 15261
2. Department of Internal Medicine and Epidemiology (K.E.E.), University of Minnesota, Minneapolis, Minnesota 55417
3. Department of Epidemiology and Biostatistics (D.C.B.), University of California, San Francisco, San Francisco, California 94105
4. Kaiser Permanente Medical Care Program (B.E.), Oakland, California 15261