Evaluating Financial Incentives as a Tool to Increase Medication Adherence for Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Introduction: Type 2 diabetes mellitus (T2DM) is a common chronic disease with high rates of complications. Although there are successful treatments, rates of medication non-adherence remain high. This study aims to evaluate the impact of financial incentives on medication adherence in people living with T2DM. Methods: PubMed, Scopus, and Embase were searched via the terms "medication adherence," "diabetes," and "financial/economic incentive." Data on study characteristics, incentive type, and impact were extracted. The outcome measures included the proportion of days covered (PDC), mean possession ratio (MPR), percent adherent (PDC/MPR > 80%), and others. Two pooled Bayesian meta-analyses were conducted, analyzing the mean differences in PDC or MPR and the percentage of adherent patients (MPR > 80%). Results: The search yielded 8244 results with 126 full-text articles reviewed. In total, 22 studies that met the inclusion criteria were included. Among these 22 studies, 16 reported that financial incentives significantly increased medication adherence in all, four reported that they did not lead to significant changes in adherence, and two studies reported differing results per subgroup. For the pooled meta-analyses, the effect of financial incentives on percent adherent was significant in three studies (weighted Cohen's D: 0.03, P = 0.02) and in the ten studies assessed PDC/MPR, financial incentives significantly increased adherence (weighted Cohen's D: 0.02, 95%, P < 0.01). Conclusion: This systematic review and meta-analysis demonstrated that financial incentives lead to statistically significant but possibly clinically irrelevant increases in medication adherence for patients living with T2DM.