Today a record three in 10 Medicare beneficiaries are enrolled in Medicare Advantage health plans, mainly HMOs and PPOs, which are paid by the government to provide Medicare benefits to their enrollees. Given the projected rise in Medicare Advantage enrollment, an important question for both consumers and policymakers is how quality and access to care compares for beneficiaries in traditional Medicare versus Medicare Advantage plans.

To try to answer this question, the Kaiser Family Foundation commissioned a comprehensive review of the literature: 45 studies published since 2000, including 40 that involve direct comparisons between traditional Medicare and Medicare Advantage plans. Conducted by lead author Marsha Gold, Senior Fellow Emeritus with Mathematica Policy Research, the analysis offers insights, but finds shortcomings in the available research, making it hard to draw broad conclusions about the relative performance of the two coverage options.

The report finds that the data used in studies that compare traditional Medicare and Medicare Advantage tend to be old and provide limited examination of the experience since 2010, when the Affordable Care Act altered the landscape. For the most part, studies reflect the experience of HMOs, not local and regional PPOs that have helped fuel the recent boom in Medicare Advantage enrollment. Because of data constraints, most studies focus on a limited set of quality and access measures, and use data based on selected states or markets, rather than the experiences of plans and enrollees nationwide.

Within those limitations, the analysis finds:

• At least through 2009, Medicare HMOs tend to perform better than traditional Medicare in providing preventive services and using resources more conservatively. These are measures where HMOs have historically been strong.

• Beneficiaries themselves continue to rate traditional Medicare more favorably than Medicare Advantage plans in terms of quality and access, though one study suggests that the difference may be narrowing for the average beneficiary. Among beneficiaries who are sick, the gap is particularly large, and favors traditional Medicare.

• Performance varies widely across Medicare Advantage plans even within the same type, which limits the ability to generalize across the program.

What Do We Know About Health Care Access and Quality in Medicare Advantage Versus the Traditional Medicare Program? concludes that better information is needed to inform policymaking and suggests strengthening available data and other support for tracking and monitoring performance across Medicare Advantage plans and traditional Medicare as each sector evolves.