Prior medication adherence of participants and non participants of a randomized controlled trial to improve patient adherence in cardiovascular risk management

BMC Med Res Methodol. 2019 May 9;19(1):95. doi: 10.1186/s12874-019-0743-7.

Abstract

Background: Poor medication adherence is a major factor in the secondary prevention of cardiovascular diseases (CVD) and contributes to increased morbidity, mortality, and costs. Interventions for improving medication adherence may have limited effects as a consequence of self selection of already highly adherent participants into clinical trials.

Methods: In this retrospective cohort study, existing levels of medication adherence were examined in self-decided participants and non-participants prior to inclusion in a randomized controlled study (RCT), evaluating the effect of an intervention to improve adherence. In addition, the non-participants were further divided into 'responders' and 'non responders'. All individuals had manifest cardiovascular disease and completed a questionnaire with baseline characteristics, the Beliefs about Medicines Questionnaire (BMQ) and the Modified Morisky Scale® (MMS®) as part of a regular screening program. A logistic regression was conducted to examine the relationship between study participation willingness, adherence level and the beliefs about medication.

Results: According to the MMS® the adherence level was comparable in all groups. In both (non)-participants groups, 36% was classified as high adherent; 46% participants versus 44% non-participants were classified as medium adherent and 19% of the participants versus 20% of the non-participants were low adherent (p = 0.91. The necessity concern differential (NCD) from the BMQ was 3.8 for participants and 3.4 for non-participants (p = 0.32).

Conclusion: This study shows that adherence to medication and beliefs about medication do not differ between participants and non-participants before consenting to participate in an RCT. The study design seems not to have led to greater adherence in the study group.

Keywords: Adherence; Informed consent; Participation; Randomized controlled trials; Selection bias.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Assessment of Medication Adherence*
  • Cardiovascular Diseases / mortality
  • Cardiovascular Diseases / prevention & control*
  • Female
  • Health Knowledge, Attitudes, Practice*
  • Humans
  • Informed Consent
  • Male
  • Medication Adherence / psychology*
  • Middle Aged
  • Retrospective Studies
  • Risk Factors
  • Risk Reduction Behavior*
  • Secondary Prevention / methods
  • Surveys and Questionnaires