How restrictive are Medicare Advantage plans?

Now that 51% of Medicare beneficiaries are enrolled in Medicare Advantage (MA), one key question is how restrictive are MA narrow networks? While beneficiaries enrolled in Medicare fee-for-service can choose any provider, MA plans can impose restrictions on enrollee’s provider choices. Measuring how restrictive an MA plan is, however, is difficult because “restrictiveness” is a concept that is difficult to quantify.

However, this is exactly what a paper by Feyman et al. (2023) aims to do. Their methodological approach uses Part D prescription drug event (PDE) and beneficiary claims data as well as geographic information from the Area Health Resource File (AHRF). Using these data, the authors developed a model:

…to predict the unique number of primary care providers that would have been seen by MA beneficiaries absent network restrictions. The model was trained and validated on Traditional Medicare (TM) beneficiaries. A pseudo-Poisson and a random forest model were evaluated. An observed-to-expected (O/E) ratio was calculated as the number of unique providers seen by MA beneficiaries divided by the number expected based the TM prediction model. Multivariable linear models were used to assess the relationship between network restrictiveness and plan and market factors. :

The authors evaluate the results based on type of plan (i.e., HMO, POS, PPO) and whether the patients are in urban or rural markets. They find that:

Health Maintenance Organization plans were more restrictive (O/E = 55.5%; 95% CI 55.3%–55.7%) than Health Maintenance Organization-Point of Service plans (67.2%; 95% CI 66.7%–67.8%) or Preferred Provider Organization plans (74.7%; 95% CI 74.3%–75.1%), and rural areas had more restrictive networks (31.6%; 95% CI 29.0%–34.2%) than metropolitan areas (61.5%; 95% CI 61.3%–61.7%). Multivariable results confirmed these findings, and also indicated that increased provider supply was associated with less restrictive networks.

The full paper can be read here.