At baseline, participants reported PCS and MCS scores of 50 and 54, respectively. these are higher than mean scores for general US population [32]. This may reflect the eligibility criteria for inclusion in the study. Participants wear initially screened to reduce the influence of such factors as comorbid conditions that would negatively impact HRQoL such as clinical depression. It is possible that over time participants tended to "regress to mean in their assessmenrts of HRQol.