Medication nonadherence in diabetes: longitudinal effects on costs and potential cost savings from improvement

Abstract

Objective: To examine the longitudinal effects of medication nonadherence (MNA) on key costs and estimate potential savings from increased adherence using a novel methodology that accounts for shared correlation among cost categories.

Research design and methods: Veterans with type 2 diabetes (740,195) were followed from January 2002 until death, loss to follow-up, or December 2006. A novel multivariate, generalized, linear, mixed modeling approach was used to assess the differential effect of MNA, defined as medication possession ratio (MPR) ≥0.8 on healthcare costs. A sensitivity analysis was performed to assess potential cost savings at different MNA levels using the Consumer Price Index to adjust estimates to 2012 dollar value.

Results: Mean MPR for the full sample over 5 years was 0.78, with a mean of 0.93 for the adherent group and 0.58 for the MNA group. In fully adjusted models, all annual cost categories increased ∼3% per year (P = 0.001) during the 5-year study time period. MNA was associated with a 37% lower pharmacy cost, 7% lower outpatient cost, and 41% higher inpatient cost. Based on sensitivity analyses, improving adherence in the MNA group would result in annual estimated cost savings ranging from ∼$661 million (MPR <0.6 vs. ≥0.6) to ∼$1.16 billion (MPR <1 vs. 1). Maximal incremental annual savings would occur by raising MPR from <0.8 to ≥0.8 ($204,530,778) among MNA subjects.

Conclusions: Aggressive strategies and policies are needed to achieve optimal medication adherence in diabetes. Such approaches may further the so-called "triple aim" of achieving better health, better quality care, and lower cost.

Figure 1

Trajectory of mean costs from the unadjusted, shared, random intercept log-normal GLMM (in $1,000 units) for each cost type over time by medication adherence status (veterans with type 2 diabetes 2002–2006). (A high-quality color representation of this figure is available in the online issue.)