Background Well-conducted, investigator-led randomized controlled trials (RCTs) are the gold standard for evaluating the efficacy of new treatments and are a key component of evidence-based medicine. It is unclear whether participating in an RCT is beneficial to the individual before the results of RCTs are known.

Purpose In a matched historical cohort study, we examined whether participation in RCTs was associated with improved health outcomes.

Methods Participants in the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE), Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), or Telmisartan Randomized Assessment Study in ACE-intolerant Subjects with Cardiovascular Disease (TRANSCEND) studies and non-participant controls were selected from patients attending outpatient clinics at Middlemore Hospital between 2001 and 2003. Read more