What Do We Know About Health Care Access and Quality in Medicare Advantage Versus the Traditional Medicare Program?

While the majority of Medicare beneficiaries still receive their benefits through the traditional Medicare program, 30 percent now obtain them through private health plans participating in Medicare Advantage. As the number of Medicare Advantage enrollees continues to climb, there is growing interest in understanding how the care provided to Medicare beneficiaries in Medicare Advantage plans differs from the care received by beneficiaries in traditional Medicare.

Despite the interest, the last comprehensive review of research evidence on health care access and quality in Medicare Advantage and traditional Medicare is more than 10 years old and did not focus exclusively on Medicare (Miller and Luft 2002). That study found that health maintenance organizations (HMOs) provide care that is roughly comparable in quality to the care provided by non-HMOs (mainly traditional indemnity insurance), and that quality varied across health plans. It also found that HMOs used somewhat fewer hospital and other expensive resources in delivering care, with enrollees rating them worse on many measures of access and satisfaction. However, the market has changed substantially over the last decade, making it important that policymakers have available more current analysis, particularly on Medicare health plans.

This literature review synthesizes the findings of studies that focus specifically on Medicare and have been published between the year 2000 and early 2014. Forty-five studies met the criteria for selection, including 40 that made direct comparisons between Medicare health plans and traditional Medicare. An additional five studies are included, even though they have no traditional Medicare comparison group, because they include a comparison of health care access and quality in different types of Medicare Advantage plans. A full list of the studies included in this analysis is found in the Works Cited.


What the Literature Shows

The review of the literature comparing quality and access provided under traditional Medicare and Medicare Advantage plans suggests the following:

  • HEDIS Effectiveness Metrics on Preventive Care. Medicare Advantage, on average, scores more highly than traditional Medicare on subsets of Medicare HEDIS indicators – primarily those pertaining to use of preventive care services. Two studies found Medicare preferred provider organizations (PPOs) outperformed traditional Medicare on some metrics (particularly mammography rates), though HMOs nevertheless performed better than PPOs. All of these studies were conducted prior to changes made by the Affordable Care Act (ACA) to improve coverage of preventive services under traditional Medicare.
  • Beneficiary Reports on Quality and Access (CAHPS). Medicare beneficiaries generally rated Medicare Advantage lower than traditional Medicare on questions about health care access and quality, especially if beneficiaries had a chronic illness or were sick; however, the difference in ratings between traditional Medicare and Medicare Advantage narrowed on some metrics by 2009 (e.g., overall care ratings). Keenan et al. (2009) found that sick beneficiaries in Medicare Advantage rated their plans substantially lower than beneficiaries of similar health status in traditional Medicare, and Elliott et al. (2011) found significantly lower CAHPS ratings (and greater disparities between Medicare Advantage and traditional Medicare) among vulnerable subgroups of beneficiaries in Medicare Advantage. Little is known about how CAHPS scores vary by type of Medicare Advantage plan since most studies are based on HMOs or periods in which HMOs were the main plan type.
  • Potentially Avoidable Hospital Admissions. Based on six studies involving beneficiaries in a limited number of states and/or plans represented by the Alliance of Community Health Plans (ACHP), Medicare beneficiaries in HMOs are less likely to be hospitalized for a potentially avoidable admission than beneficiaries in traditional Medicare. Four of these studies rely on data prior to 2006, and reflect HMO experiences in mature markets.
  • Readmission Rates. While a number of studies examine whether readmission rates differ among beneficiaries in Medicare Advantage and traditional Medicare, the evidence from these studies is inconclusive because findings differ across the studies and many studies lack adjustments for important potentially confounding factors.
  • Health Outcomes. There is some evidence that good coverage, as defined by relatively low cost-sharing (whether through Medicare HMOs or through Medicare with supplemental coverage), may result in earlier diagnoses of some cancers compared to traditional Medicare alone. Treatment patterns for some cancers also may differ between Medicare HMOs and traditional Medicare, but studies do not show that this affects patient outcomes. However, the age of the studies, the gaps in controls for selection, and the evolving nature of guidelines for appropriate care limit the conclusions that can be drawn.
  • Resource Utilization. Medicare HMOs appear to provide a less resource-intensive style of practice than traditional Medicare, as measured in studies examining end-of-life care, use of certain procedures, and overall utilization rate in HMOs, especially for hospital services. However, most of these studies provide little direct evidence of whether less intensive care is better or worse or how the appropriateness of care differs between Medicare Advantage and traditional Medicare.
  • Variation by Geography, by Plan Type, and by Plan Experience. On a variety of metrics, performance among Medicare Advantage plans varies substantially across plans, even among plans of the same plan type. The variations by market in more established HMOs with integrated delivery systems tend to be more represented in existing research, and to perform better. Performance on quality and access metrics varies across geographic areas, and the variations in Medicare Advantage and traditional Medicare ratings are not necessarily the same.
The Available Evidence has Substantial Limitations

To make a definitive comparison of both quality and access in traditional Medicare and Medicare Advantage plans, one would ideally draw from studies with relatively recent data that is nationally representative in terms of both the characteristics of health plans participating in Medicare Advantage and the characteristics of beneficiaries covered by the Medicare program. Performance measures would capture a broad range of metrics assessing both quality of care and access to care, and would include enrollees’ assessments, process measures, and outcome measures. The comparisons would adjust for factors that might explain differences in performance between Medicare Advantage and traditional Medicare, such as variations in medical practice by geographical location and patient health status. In an ideal world, studies would provide information to help clarify if differences vary by plan type, and how quality and access indicators compare for the typical Medicare beneficiary, as well as beneficiaries who are in relatively poor health with significant medical needs.

Unfortunately, while available evidence provides some insights, it falls short on many desirable dimensions. The most serious shortfalls are in the lack of timely data, the primary focus on HMOs rather than the full range of Medicare Advantage plans, and study populations that exclude important subgroups of beneficiaries (such as the under-65 disabled) and lack information on the experience of vulnerable subgroups of beneficiaries, such as those in poor health or with significant needs. In addition, available metrics are limited in their ability to capture performance across the full continuum of care and care for the total patient, particularly on a national basis.

Our review of the literature comparing quality and access measures between traditional Medicare and Medicare Advantage finds:

  • Limited Insight into Experiences After Implementation of the Affordable Care Act (ACA). With one limited exception involving hospice care, none of the 40 studies comparing Medicare Advantage to traditional Medicare rely on data from 2010 or later. Thus, it is not yet possible to assess the performance of Medicare Advantage relative to traditional Medicare that reflects plan performance after the implementation of the Medicare Advantage payment changes included in the ACA (payment reductions, coupled with quality bonus payments). Fourteen of the 40 studies report only on experience in the 1990s or earlier, and of the 27 others covering the 2000-2009 period, 16 provide estimates between 2006 and 2009, after the introduction of the Medicare prescription drug benefit.
  • Studies Reflect Mainly HMO Experience, Not Newer Plan Types. Almost all of the literature applies to the experience of beneficiaries in HMOs, rather than in the full range of plans that are currently available. In 2014, for example, one-third of all Medicare Advantage enrollees are in plans other than HMOs, mainly PPOs. Only three of the 40 studies that compared traditional Medicare to Medicare Advantage (and two of the five that compared Medicare Advantage plans only) included findings that were specific to Medicare PPOs. Others either are limited to HMOs, apply to a period when HMOs were the overwhelming plan type, or do not analyze data by plan type. As a result, the results are not generalizable to the Medicare Advantage program as a whole as contrasted with the experience of its older HMO component.
  • Limited Insight into the Experience of Beneficiaries with More Complex Medical Needs. Few of the existing studies provide insight on how Medicare Advantage and traditional Medicare perform on quality and access metrics for beneficiaries whose health characteristics suggest that they could have more complex needs. Only four studies, all based on beneficiary survey data, focused explicitly on subgroups of the Medicare population defined by the authors as high-need based on health or functional status (Keenan et al. 2009, Elliott et al. 2011, Pourat et al. 2001, and Beatty and Dhont 2001). One study (Elliott et al. 2011) also examined disparities in care for vulnerable subgroups defined by various socioeconomic indicators, along with health status. The inability to reflect the experiences of beneficiaries with significant health needs is a major limitation in the literature.
  • Data Constraints Limit National Studies. While several studies are national in scope (plans and beneficiaries), the metrics they include are limited by available data. Of the 17 national studies comparing Medicare Advantage to traditional Medicare (of 40 in total), 10 rely exclusively on CAHPS or other national population surveys, and seven use HEDIS data compared to claims data for traditional Medicare. Vital statistics data dealing with mortality were used in two of the studies as well. Studies on many metrics relevant to quality either do not exist (like intermediate outcomes for beneficiaries with multiple chronic conditions or the personal experience with care of these patients) or, like studies of potentially avoidable admissions and readmissions, depend on data from a limited set of states or locales.


Despite great interest in comparisons between traditional Medicare and Medicare Advantage, studies comparing overall quality and access to care between Medicare Advantage plans and traditional Medicare tend to be based on relatively old data, and a limited set of measures.

On the one hand, the evidence indicates that Medicare HMOs tend to perform better than traditional Medicare in providing preventive services and using resources more conservatively, at least through 2009. These are metrics where HMOs have historically been strong. On the other hand, beneficiaries continue to rate traditional Medicare more favorably than Medicare Advantage plans in terms of quality and access, such as overall care and plan rating, though one study suggests that the difference may be narrowing between traditional Medicare and Medicare Advantage for the average beneficiary. Among beneficiaries who are sick, the differential between traditional Medicare and Medicare Advantage is particularly large (relative to those who are healthy), favoring traditional Medicare. Very few studies include evidence based on all types of Medicare Advantage plans, including analysis of performance for newer models, such as local and regional PPOs whose enrollment is growing.

As the beneficiary population ages, better evidence is needed on how Medicare Advantage plans perform relative to traditional Medicare for patients with significant medical needs that make them particularly vulnerable to poorer care. The ability to assess quality and access for such subgroups is limited because many data sources do not allow subgroups to be identified or have too small a sample size to support estimates. Also, in many cases, metrics employed may not be specific to the particular needs or the way a patient’s overall health and functional status or other comorbid conditions influence the care they receive.

At a time when enrollment in Medicare Advantage is growing, it is disappointing that better information is not available to inform policymaking. Our findings highlight the gaps in available evidence and reinforce the potential value of strengthening available data and other support for tracking and monitoring performance across Medicare Advantage plans and traditional Medicare as each sector evolves.


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