Geographic Variation in the Prevalence of High-Risk Medication Use Among Medicare Part D Beneficiaries by Hospital Referral Region

BACKGROUND: Understanding geographic patterns of high-risk medication (HRM) prescribed and dispensed among older adults may help the Centers for Medicare & Medicaid Services and their partners develop and tailor prevention strategies. OBJECTIVE: To compare the geographic variation in the prevalence of HRM use among Medicare Part D beneficiaries from 2011 to 2013, for Medicare Advantage Prescription Drug (MA-PD) plans and stand-alone Prescription Drug Plans (PDPs). METHODS: This retrospective study used the data of a 5% national Medicare sample (2011-2013). Beneficiaries were included in the study if they were aged ≥ 65 years, continuously enrolled in MA-PDs or PDPs (~1.3 million each year), and had ≥ 2 prescriptions for the same HRM (e.g., amitriptyline) prescribed and dispensed during the year based on the Pharmacy Quality Alliance’s (PQA) quality measures for HRM use. Multivariable logistic regression was used to estimate adjusted annual HRM use rates (i.e., adjusted predictions, average marginal predictions, or model-adjusted risk) across 306 Dartmouth Atlas of Health Care hospital referral regions (HRRs), controlling for sociodemographic, health-status, and access-to-care factors. RESULTS: Among eligible beneficiaries each year (1,161,076 in 2011, 1,237,653 in 2012, and 1,402,861 in 2013), nearly 40% were enrolled in MA-PD plans, whereas the remaining 60% were in PDP plans. The adjusted prevalence of HRM use significantly decreased among Medicare beneficiaries enrolled in MA-PD (13.1%-8.4%, P < 0.001) and PDP (16.2%-12.2%, P < 0.001) plans from 2011 to 2013. For MA-PD and PDP beneficiaries, HRM users were more likely to be (all P < 0.001) the following: female (MA-PD: 70.4% vs. 59.9%; PDP: 72.8% vs. 62.5%); White (MA-PD: 84.6% vs. 81.4%; PDP: 86.6% vs. 85.3%); with low-income subsidy or dual eligibility for Medicaid (MA-PD: 22.3% vs. 16.6%; PDP: 29.2% vs. 23.3%); and disabled (MA-PD: 15.6% vs. 8.7%; PDP: 15.4% vs. 8.5%) compared with non-HRM users in 2013. In 2013, significant geographic variation existed, with the ratios of 75th-25th percentiles of HRM use rates across HRRs as 1.42 for MA-PDs and 1.31 for PDPs. For MA-PDs, the top 5 HRRs with the highest HRM use rates in 2013 were Casper, WY (20.4%), Waco, TX (16.7%), Lubbock, TX (15.7%), Santa Barbara, CA (15.2%), and Temple, TX (15.1%); for PDPs, they were Lawton, OK (18.8%), Alexandria, LA (18.8%), Lake Charles, LA (18.6%), Oklahoma City, OK (18.0%), and Slidell, LA (18.0%). CONCLUSIONS: Substantial geographic variation exists in the prevalence of HRM use among older adults in Medicare, regardless of prescription drug plan. Areas with high prevalence of HRM use may benefit from targeted interventions (e.g., medication therapy management monitoring or alternative medication substitutions) to prevent potential adverse consequences.