Trial Conduct
.Participants were recruited using mass mailings, community-based screening, and mass-media announcements. Enrollment began in January 2000 and ended in June 2001. For logistical purposes, participants were enrolled in 3 or 4 cohorts at each center. Baseline data were collected during 3 screening visits and a randomization visit, each scheduled at least 7 days apart. Follow-up data were collected at 1 visit 3 months after randomization and at 3 visits 6 months after randomization. Participant flow during the trial is shown in