The economics of improving medication adherence in osteoporosis: validation and application of a simulation model

Abstract

Context: Adherence to osteoporosis treatment is low. Although new therapies and behavioral interventions may improve medication adherence, questions are likely to arise regarding their cost-effectiveness.

Objective: Our objectives were to develop and validate a model to simulate the clinical outcomes and costs arising from various osteoporosis medication adherence patterns among women initiating bisphosphonate treatment and to estimate the cost-effectiveness of a hypothetical intervention to improve medication adherence.

Design: We constructed a computer simulation using estimates of fracture rates, bisphosphonate treatment effects, costs, and utilities for health states drawn from the published literature. Probabilities of transitioning on and off treatment were estimated from administrative claims data.

Setting and patients: Patients were women initiating bisphosphonate therapy from the general community.

Intervention: We evaluated a hypothetical behavioral intervention to improve medication adherence.

Main outcome measures: Changes in 10-yr fracture rates and incremental cost-effectiveness ratios were evaluated.

Results: A hypothetical intervention with a one-time cost of $250 and reducing bisphosphonate discontinuation by 30% had an incremental cost-effectiveness ratio (ICER) of $29,571 per quality-adjusted life year in 65-yr-old women initiating bisphosphonates. Although the ICER depended on patient age, intervention effectiveness, and intervention cost, the ICERs were less than $50,000 per quality-adjusted life year for the majority of intervention cost and effectiveness scenarios evaluated. Results were sensitive to bisphosphonate cost and effectiveness and assumptions about the rate at which intervention and treatment effects decline over time.

Conclusions: Our results suggests that behavioral interventions to improve osteoporosis medication adherence will likely have favorable ICERs if their efficacy can be sustained.

Fig. 1.

Model structure. Patients enter the model distributed between the on-treatment health states, excluding dead. In each simulated 3-month cycle, patients may experience no clinical event, a fracture, or death. Patients who remain alive and have been on treatment can remain on treatment or discontinue treatment; patients who have been off treatment can remain off treatment or reinitiate treatment. Patients begin the next cycle in a state determined by their clinical event history and most recent medication events. The process is repeated until all patients are dead.

Fig. 2.

Validation of model-based projections against data on bisphosphonate use under usual care. Percentage of patients on treatment (A) and persistent with treatment (B) by 90-d interval since bisphosphonate initiation under usual care. Persistence is defined as continuous bisphosphonate use without a gap in use of at least 30 d.

Fig. 3.

One-way sensitivity analyses. Each bar represents the incremental cost-effectiveness ratio of the adherence intervention for different assumptions concerning the parameter listed. The vertical line depicts the incremental cost-effectiveness ratio when all parameters are set at their base case values (listed in parentheses beside the parameter name).

Fig. 4.

Two-way analysis on intervention cost and intervention effectiveness. Each block represents a possible intervention characterized by its cost and effectiveness. The color coding denotes the cost-effectiveness of the intervention.