A systematic review of medication adherence and mortality in chronic disease : implications for clinical guidelines and policy

Abstract

OBJECTIVES : This systematic review aims to investigate whether good medication adherence in adults with chronic conditions is associated with a lower mortality risk compared to poor adherence within published literature, and the extent to which this relationship is represented within South African policy and legislation. METHODS : A systematic search of three electronic databases-PubMed, MEDLINE (Ovid) and Scopus-was conducted. Only primary research articles published in English after March 2004 and with study populations >18 years of age were considered. South African health legislation and professional guidelines from 2014 onwards were sourced using search terms aligned with the systematic review strategy and systematically analysed. RESULTS : Twenty-six articles were included in the systematic review. Effect measures included hazard ratios (HR), incidence rate ratios (IRRs) and odds ratios (OR), where values greater than 1 indicate a higher risk of mortality. The effect measures from individual studies were categorized according to adherence levels: good, intermediate, poor and non-adherent. A total of 17 effect measures were reported for good adherence, only one of which was greater than 1. There were 44 effect measures reported for intermediate, poor and non-adherence categories, all of which were greater than 1. Pooled estimates for poor adherence and non-adherence had the highest HRs (HR = 1.63; 95% confidence interval [CI]: 1.36-1.96 and HR = 2.77; 95% CI: 2.3-3.34 respectively). Review of South African health legislation and professional guidelines showed a dominance of mortality-related terms (1.323 and 2.98 matches per 1000 words for 'mortality' and 'death', respectively) compared with adherence-related terms (0.053-2.98 matches per 1000 words). Co-occurrence between medication adherence-related search terms (MARS, adherence, medication adherence, adhere, non-adherence and medication compliance) and mortality-related search terms (death, mortality and survival) was low within all documents analysed. CONCLUSION : The systematic review demonstrates a clear relationship between good adherence to chronic medication and a lower mortality risk. However, the review of legislative and policy documents suggests that government efforts are focused primarily on surveillance, rather than strategy or preventative measures. This strong evidence should motivate incorporating adherence-based risk assessments into clinical and legal frameworks.