Background: Patient adherence affects treatment efficacy, and surprisingly, adherence is frequently associated with reductions in mortality for those receiving placebo. Methods: This study considers the role of trial adherence for men (N = 12,338) in the Multiple Risk Factor Intervention Trial (MRFIT), a prospective study of 9-year follow-up mortality following randomization to Special Intervention (SI) or Usual Care (UC). Annual visit attendance rates were used as a measure of adherence. Results: A significant Adherence x Group Assignment interaction (p = .002) revealed that SI significantly reduced cardiovascular disease (CVD) mortality for highly adherent participants, RR = .91 (95% confidence interval [CI] = .84-.99) but significantly increased CVD mortality for poorly adherent participants, RR = 1.28 (95% CI = 1.05-1.57) when compared to UC. These associations remained after controlling for baseline characteristics (e.g., income), reported illness, or occurrence of a nonfatal CVD event during the trial. The beneficial effect of SI among the adherent participants was partly due to reduced smoking and diastolic blood pressure levels during the trial. Conclusions: SI significantly reduced the risk of CVD mortality for participants adherent with the MRFIT, and this effect was accounted for by positive changes in CVD risk factors. These findings suggest a method for evaluating treatment efficacy in subgroups determined by patient responses (e.g., adherence to annual assessment visits) to the treatment program after randomization.
ASJC Scopus subject areas
- Psychiatry and Mental health