The Release of Medicare Advantage Data: What Does It Mean for Researchers?

Over 58 million Americans are enrolled in Medicare. Of those, 20.2 million, approximately 34%, receive their Medicare through a private Medicare Advantage (MA) plan, rather than traditional fee-for-service (FFS) Medicare. That’s why the recent announcement by Centers for Medicare and Medicaid Services (CMS) that MA data will be available to researchers beginning this Fall is so exciting.

To date, research on MA has been limited because almost no data is available. CMS publishes aggregate MA enrollment by county. Researchers can also get some information on quality for MA plans through HEDIS and some have obtained small amounts of MA claims data. But detailed data have not been made available in a comprehensive or representative way.

Image from Kaiser Family Foundation


This stands in contrast to data for FFS Medicare, which has long been available in a variety of formats. “Research identifiable files” (RIFs) are the most useful for researchers, providing patient-level enrollment and encounter data. Enrollment data contains patient-level information such as demographics, while encounter data contains utilization information like place of service, diagnoses, procedures, and prices. These files can also be linked to other datasets (such as NIH’s SEER (Surveillance, Epidemiology, and End Results), the national retirement survey, and the national death index) to create rich datasets.

The robust Medicare FFS data has supported a lot of research on FFS Medicare. But what’s happening in FFS Medicare doesn’t necessarily reflect what’s happening in MA, for a variety of reasons. One is that people who select into MA are different than people who select into FFS Medicare. MA plans often offer lower premiums than FFS Medicare, and some MA plans have enhanced benefits like dental and vision coverage and wellness programs like Silver Sneakers. MA enrollees also accept a managed care approach, which may include more limited or tiered provider networks and more restrictions on services through referral requirements.

Payment to MA plans also creates different incentives in the way MA plans and providers behave. Plans are paid a capitated per patient per month rate, plus additional payments for risk adjustment and quality. MA has ended up costing the government more than FFS Medicare, despite delivering care at a lower cost.

In some states, MA represents such a large share of the Medicare market that trends in FFS are only part of the picture. In Minnesota 56% of Medicare enrollees choose an MA plan, while over 40% do in both Florida and California. Research is particularly crucial in these states.

The MA data will help address these gaps and countless others related to our understanding of the Medicare market.

In late fall, MA RIF files will be available for 2015 encounters, which will cover six settings: inpatient, skilled nursing facility (SNF), home health, institutional outpatient, carrier, and durable medical equipment. Part D data (pharmacy) are available separately. The data are expected to be updated annually. The MA RIF data can be linked to all other CMS files using a beneficiary ID number, which means researchers can identify unique individuals across government insurance types. This allows researchers to investigate characteristics and drivers of Medicare switching behaviors (between FFS and MA), and even link enrollees who participate in other government programs such as Medicaid.

A plan characteristics file will also be available, allowing researchers to analyze or control for plan level factors. These include information on plan premiums, cost sharing tiers, service area, and special plan types like special needs plans (SNPs).

As with any claims data, there are limitations. Claims data exist to maintain records of reimbursement, so it does a good job at capturing variables that are important for paying bills, but is not as good for other data. Diagnosis data only includes diagnoses that were documented by a provider at the visit, so they are sometimes incomplete and not always sufficiently specific. Claims don’t provide physical measurements like blood pressure or BMI. They also don’t provide any information about people who haven’t visited a doctor, services that don’t bill the plan (such as vaccinations received at a supermarket pharmacy), or services not covered by Medicare. For beneficiaries without Part D coverage, pharmacy data are not available.

From a practical perspective, there are significant barriers to obtaining Medicare data, so it’s most practical for groups with long-term research plans in the Medicare space. In addition to a lengthy and involved application process and significant time to understand the files, the data are quite expensive. Price is based on the types and size of files requested, but in general researchers should expect a sample to cost several thousand dollars per year of data requested. Unlike many data sources, CMS does not offer lower fees for students or researchers.

Despite limitations, the MA data release is a big opportunity for researchers. If you’re interested in obtaining Medicare data, information can be found through ResDac, the CMS contractor that provides assistance with CMS data for academic, non-profit and government researchers.