Institutional review board approval was obtained from the Kaiser Research Foundation Institute and the University of California, San Francisco. At the baseline recruitment we obtained written informed consent for 6- and 12-month interviews, and at 6 months we obtained permission to contact participants for future interviews. Specific verbal consent to conduct 5-year, 7-year, 9-year, and 11-year interviews was obtained from participants at the beginning of each interview (and permission to contact for future interviews was asked at the end of each interview). Response rates at 5, 7, 9, and 11 years for the surviving cohort were 80.2%, 75.1%, 73.7% and 72.2%, respectively.
