The effects of patient out-of-pocket costs for insulin on medication adherence and health care utilization in patients with commercial insurance; 2007-2018.

ABSTRACT

BACKGROUND: High out-of-pocket costs (OOPCs) for insulin can lead to cost-related nonadherence and poor outcomes, prompting payers to limit insulin OOPCs. However, data are scarce on whether insulin OOPCs at policy-relevant levels is associated with improved adherence and outcomes. OBJECTIVE: To identify associations between insulin OOPCs and insulin adherence, noninsulin antihyperglycemic (AHG) medication adherence, and diabetes-related emergency department (ED) visits and hospitalizations. METHODS: This retrospective cohort study was conducted using OptumLabs Data Warehouse, a longitudinal, real-world data asset with deidentified administrative claims and electronic health record data. Individuals with type 1 diabetes (T1D) or type 2 diabetes (T2D), insulin use on January 1 of a study year (index date 2007-2018), continuous commercial health plan eligibility 12 months pre-index and post-index date, and at least 1 insulin claim during the 12-month follow-up period were included. Average insulin OOPCs per 30-day supply in the follow-up period was identified and categorized ($0, > $0-$20 [referent group], > $20-$35, > $35-$50, and > $50). The proportion of patients with a gap in insulin supply of 60 or more continuous days, AHG nonadherence per modified proportion of days covered less than 0.80, and a diabetes-related ED visit or hospitalization were identified and compared by insulin OOPC category vs more than $0 to $20 using pairwise chi-square tests and multivariable logistic regression. RESULTS: The study included 21,085 individuals with T1D and 72,512 with T2D. Patients with average OOPCs more than $50 were more likely to have a gap in insulin supply vs those with OOPCs more than $0 to $20, with an odds ratio (OR) of 1.14 (95% CI =1.05-1.24) and 1.38 (95% CI = 1.32-1.45) for T1D and T2D, respectively. Those with T2D and OOPCs more than $35 were also more likely to have a 60-day gap in insulin supply (OR 1.17; 95% CI = 1.11-1.23). Odds of having a diabetes-related hospitalization or ED visit did not increase with higher OOPCs; rather, associations tended to be inverse. Nonadherence to AHG medications in the T2D cohort was higher with insulin OOPCs more than $20 vs those more than $0-$20 (P < 0.05 for all). CONCLUSIONS: Individuals with T2D were more likely to have a 60-day gap in insulin supply when the OOPC was more than $35 per 30-day supply and with the OOPC more than $50 in those with T1D. These findings suggest that health plans can facilitate adherence to insulin therapy and possibly to noninsulin AHG medications by protecting patients with diabetes from experiencing high insulin OOPC. A study with a longer follow-up period is warranted to fully assess ED and hospitalization outcomes. DISCLOSURES This study was funded by the Robert Wood Johnson Foundation, Health Data for Action Research Program. The study sponsor played no role in the design or conduct of this study. The views expressed here do not necessarily reflect the views of the Foundation.