Association Between the Declining Conversion Factor and Access to Care for Medicare Beneficiaries.

CMS has maintained budget neutrality in the Medicare Physician Fee Schedule through decreases in the conversion factor, but reduced reimbursement may have secondary access-to-care consequences for Medicare beneficiaries. Hence, this study examined the association between inflation-adjusted conversion factor declines and changes in care utilization for various socioeconomically defined subgroups of Medicare beneficiaries. Using all claims from a nationally representative 5% sample of Medicare fee-for-service beneficiaries, we determined by year (2005-2023) whether beneficiaries used care. Care utilization was compared between subgroups: metropolitan versus small/rural communities, high-income versus low-income communities, and least-deprived versus most-deprived (Area Deprivation Index [ADI]) communities. Care-utilization rates were normalized to account for within and between year differences in subgroup characteristics using multivariable logistic regression. Care-utilization gaps were computed as the difference in normalized utilization values between subgroups. The temporal association between gap size and the inflation-adjusted conversion factor was assessed with linear regression. There were 32,764,305 beneficiary years (4,662,729 unique beneficiaries) that met the selection criteria. Over the 2005-2023 period, the care-utilization gaps for any physician care increased 1.76, 5.89, and 3.82 percentage points for the urbanicity, community-income, and ADI gaps, respectively. Gap growth was significantly associated with the inflation-adjusted conversion factor, which decreased 48.3% between 2005 and 2025. This inflation-adjusted conversion factor decrease was associated with care-utilization gap increases of 2.46 (urbanicity), 7.00 (community-income), and 5.31 (ADI) percentage points across all physicians. Percentage-point gap increases varied by specialty and were largest for family practice physicians: 21.31 (urbanicity), 14.02 (community-income), and 19.55 (ADI) percentage points. Hence, decreased reimbursement resulting from the Medicare budget neutrality mandate may exacerbate disparities in access to care for traditionally underserved Americans.