(CSPOT07) Factors Associated with Adherence to Long-Acting Injectable Antipsychotics Among Medicare Beneficiaries

Background: US Medicare beneficiaries in fee-for-service (FFS) and Medicare Advantage (MA) health plans are thought to represent different subsamples with respect to demographics and medication adherence. Real-world evidence on this topic is limited. However, this information is important for generalizing findings to the older US adult population. To address this gap, we examined Medicare FFS and MA beneficiaries who initiated a long-acting injectable (LAI) antipsychotic.

Objectives: To identify demographic, clinical, and healthcare service factors associated with adherence to LAI antipsychotics among Medicare beneficiaries enrolled in FFS or MA plans.

Methods: A new user retrospective cohort study included US Medicare beneficiaries aged 18 or older derived from a 5% random sample from the Centers for Medicare and Medicaid Services’ Chronic Condition Warehouse (FFS cohort) and from the Healthcare Integrated Research Database (HIRD®) maintained by Carelon Research (MA cohort). New users had at least one LAI antipsychotic anytime from 07/01/2017-12/31/2020 with no use in the one year (baseline period) preceding the date of the first LAI medical or prescription claim (index date). Inclusion criteria were continuous medical and pharmacy enrollment for ≥12 months prior to and after the index date (follow-up period). We excluded those with ≥2 different LAIs dispensed on the index date. LAI adherence in the follow-up period was defined as the proportion of days covered (PDC) ≥0.8. Multivariable logistic regression models identified baseline factors associated with LAI adherence.

Results: We identified 3,159 FFS- and 523 MA-enrolled new LAI antipsychotic users. The FFS cohort was 56% male, 51% aged 40-64 years, and 59% White with a mean of 4.6 (SD 3.5) chronic medical and 3.3 (SD 2.4) behavioral health comorbidities. The MA cohort was 45% male, 56% aged 40-64 years, and 66% White with a mean of 5.4 (SD 3.3) chronic medical and 3.5 (SD 2.3) behavioral health comorbidities. The mean PDC was 0.52 (SD 0.34) for FFS and 0.46 (SD 0.34) for MA, and 33% (FFS)/27% (MA) were classified as adherent. Significant correlates of adherence in FFS included male (OR: 1.24; 95%CI: 1.05-1.45), aged 18-39 (OR:1.69; 95%CI: 1.26-2.26), behavioral health comorbidities (OR: 0.87; 95%CI: 0.84-0.91), and atypical index LAI (OR: 1.57; 95%CI: 1.30-1.88). Odds ratios were similar in the MA cohort.

Conclusions: Our study is one of few to capture a representative sample of US Medicare enrollees in FFS and MA plans and showed that only one-third were adherent to LAIs. The demographic characteristics and type of LAI were significant correlates of adherence in both FFS and MA Medicare enrollees, suggesting similarities between the groups.