Determinants of medication adherence in patients with acute coronary syndrome: a secondary analysis of a randomised clinical trial.

Background: Coronary heart disease (CHD) remains a leading cause of mortality and disability worldwide. Approximately half of the patients who have had a prior hospital admission for CHD will have a recurrent coronary event, with the majority of these occurring within 12 months. Despite well-established evidence-based therapies, medication non-adherence is highly prevalent and reasons for medication non-adherence are poorly understood. This study evaluates factors influencing adherence to secondary prevention medications in people with acute coronary syndrome (ACS).

Methods: We performed a secondary analysis of TEXT messages to improve MEDication adherence and Secondary prevention after ACS (TEXTMEDS), a single-blind randomised clinical trial of 1424 patients with ACS from 18 hospitals across Australia. The primary outcome was self-reported medication adherence to each of up to five classes of guideline-recommended cardioprotective medications indicated for secondary prevention after ACS. Patients were followed up at 6-month and 12-month time points and were defined as adherent if at both time points, the proportion of indicated medications taken was >80% (>24/30 days in the preceding 1 month) for all five classes if not otherwise contraindicated. Logistic regression analysis and the Least Absolute Shrinkage and Selection Operator regularisation technique were used to assess the effect of sociodemographic and clinical factors on medication adherence.

Results: The analyses included 1379 participants with complete adherence data (mean age 58.5±10.7 years; 1095 (79.4%) men). The following variables were associated with adherence to cardiovascular medications at both 6 and 12 months: greater number of total medications taken (OR: 1.33; 95% CI: 1.25 to 1.42) and attending a cardiac rehabilitation programme (1.47; 95% CI: 1.17 to 1.86). In contrast, female sex (0.67; 95% CI: 0.50 to 0.90) and physical disability (0.43; 95% CI: 0.23 to 0.77) were associated with lower likelihood of medication adherence.

Conclusions: Sociodemographic and clinical factors may influence medication adherence. Greater awareness, discussion and monitoring of these factors during patient follow-up may help improve medication adherence.

Trial Registration Number: Australian New Zealand Clinical Trials Registry; URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=364448; registration number: ACTRN12613000793718.