Disparities in Surgical Outcomes in Medicare Advantage vs Traditional Medicare

ABSTRACT

Objective: To evaluate differences in disparities in surgical outcomes between beneficiaries enrolled in Medicare Advantage (MA) vs traditional Medicare (TM).

Study Design: We conducted a retrospective cross-sectional study of Medicare beneficiaries 65 years and older undergoing common abdominal operations (appendectomy, cholecystectomy, colectomy, hernia repair) between 2016 and 2020. The primary exposures were enrollment in MA and race/ethnicity.

Methods: We performed propensity score–weighted difference-in-disparities analyses comparing Black-White and Hispanic-White disparities in MA vs TM for in-hospital mortality and 30-day mortality, complications, serious complications, and readmissions.

Results: Overall, 1,603,887 Medicare beneficiaries were included in the study, of whom 35% were enrolled in MA. Enrollment in MA was associated with no differences in Black-White disparities in postoperative mortality or complications. Hispanic-White disparities in 30-day mortality were 0.83 percentage points smaller (95% CI, –1.41 to –0.25; P = .01) and in postoperative complications were 1.24 percentage points smaller (95% CI, –2.16 to –0.32; P = .01) for MA beneficiaries compared with TM beneficiaries. There were no differences in disparities between MA and TM for readmissions.

Conclusions: MA was associated with no differences in Black-White disparities, smaller Hispanic-White disparities in postoperative mortality and complications, and no differences in readmissions. These findings may reflect potential features of MA that narrow gaps in surgical disparities but not uniformly. Future work should examine mechanisms that could impact perioperative outcomes for racial/ethnic minorities, including referral networks, care management, or cost sharing.

Am J Manag Care. 2026;32(5):e159-e166. https://doi.org/10.37765/ajmc.2026.89941

Takeaway Points

This study compared disparities in surgical outcomes between beneficiaries enrolled in Medicare Advantage vs traditional Medicare.

• Medicare Advantage was associated with smaller Hispanic-White disparities in mortality and complications and no differences in readmission disparities.
• Our findings were driven by larger reductions of adverse outcomes in racial/ethnic minority patients compared with White patients within Medicare Advantage.
• This underscores the need to identify features of Medicare Advantage, such as referral networks or perioperative care management, that could be more advantageous for racial/ethnic minority populations to help reduce disparities.

As of 2023, more than half of Medicare beneficiaries were enrolled in Medicare Advantage (MA).¹ In contrast to traditional Medicare (TM), which is administered by CMS, MA is administered by private health insurance companies. It differs from TM by frequently including supplemental benefits such as dental and vision coverage, utilization management tools to restrict use of certain services, and more restrictive provider networks. The significant enrollment growth in MA during the past 15 years has been greatest among racial/ethnic minority beneficiaries, dually enrolled beneficiaries, and beneficiaries from the most disadvantaged neighborhoods.² Enrollment from racial/ethnic minority groups has also been frequently concentrated in plans that are lower quality and plans that have higher disenrollment rates.^2-6 This has raised concerns about how MA may impact the quality of care for vulnerable patient populations that experience disparities in care. This is pertinent for surgical populations given that more than half of total annual Medicare payments are attributable to surgical care.⁷

Whether MA enrollment is associated with reduced disparities in surgical outcomes for racial/ethnic minority beneficiaries is unknown. Prior work has focused primarily on outpatient access and utilization, with mixed results on whether racial/ethnic minority beneficiaries in MA had higher rates of preventive care services compared with those in TM.^8-11 A recent systematic review of MA vs TM found insufficient evidence to determine whether MA or TM more effectively mitigates racial/ethnic disparities.¹² Studies of surgical conditions are more limited, but a single-state study demonstrated that MA was associated with almost double the racial disparity in readmission rates after major surgery compared with TM.¹³ To date, there has been no nationally representative study of differences in disparities between MA and TM for common surgical conditions.

It is crucial to understand whether MA promotes equitable surgical care, especially as MA plans face increased scrutiny due to potential denials of medically necessary care, significant overpayments, and higher per-enrollee costs compared with TM.^14-17 In this context, we conducted a study to evaluate whether enrollment in MA was associated with smaller or larger racial and ethnic disparities in postoperative outcomes for beneficiaries undergoing 1 of 4 common surgical procedures (appendectomy, cholecystectomy, hernia repair, and colectomy) that have been previously used in evaluating Medicare coverage and surgical quality.¹⁸

METHODS

Data Source and Patient Population

This was a retrospective cross-sectional study using data from the 100% capture Medicare Provider Analysis and Review (MedPAR) file between 2016 and 2020. MedPAR is a data set maintained by CMS containing detailed information about Medicare beneficiaries who are admitted to hospitals, including data on inpatient stays, diagnoses, procedures, discharge information, and hospital characteristics.¹⁹ Additional hospital characteristics (bed size, region, teaching status, patient-to-nurse ratio) were obtained from the American Hospital Association (AHA) Annual Survey, a comprehensive survey conducted yearly by the AHA that includes detailed information on more than 95% of hospitals.²⁰ Each admission was linked to a hospital by a unique hospital identifier located in the MedPAR file. The study was approved by the University of Michigan Institutional Review Board and deemed exempt due to the use of deidentified secondary data.

Patients aged 65 to 99 years who underwent 1 of 4 common general surgery procedures were included. We identified patients who underwent appendectomy, cholecystectomy, colectomy, or hernia repair using procedure codes from the International Classification of Diseases (ICD), Tenth Revision, Clinical Modification and ICD, Tenth Revision, Procedure Coding System. We chose these operations because they represent some of the most common elective and emergent general surgery procedures. A full list of the ICD codes used for this study can be found in eAppendix Table 1 (eAppendix available at ajmc.com).

The exposures of interest were enrollment in MA and race/ethnicity. MA enrollment was determined by enrollment in Medicare Part C during the month of the operation within the MedPAR file, which identifies patients who receive their Medicare benefit via an MA plan. This analysis uses the race and ethnicity information from Medicare’s enrollment data (beneficiary race code), which is based on data collected from the Social Security Administration.²¹ Although this information is currently the best available for the entire Medicare population, comparisons to self-reported data show that race and ethnicity are still misclassified for some enrollees, particularly American Indian/Alaska Native, Asian/Pacific Islander, and Hispanic beneficiaries.²² Race was dichotomized as either Black or non-Hispanic White. Ethnicity was dichotomized as either Hispanic or non-Hispanic. Race and ethnicity were then classified as the mutually exclusive categories of non-Hispanic Black, Hispanic, and non-Hispanic White (hereafter referred to as Black, Hispanic, and White, respectively).

Outcomes

The primary outcome was the rate of 30-day mortality of beneficiaries undergoing the included surgical procedures. Mortality was determined in 2 ways. First, vital status at the time of discharge was used to identify in-hospital mortality. Second, the denominator file was used to identify deaths within 30 days of discharge from the index operation.

Secondary outcomes included 30-day complications, serious complications, and readmissions. Complications were identified using ICD, Ninth Revision and International Statistical Classification of Diseases, Tenth Revision codes, previously described and validated in studies using the MedPAR file.^23,24 Serious complications were defined as having at least 1 complication and a length of stay greater than the 75th percentile for the specific procedure. We added this criterion, as done previously, to identify complications that had a significant impact on the patient’s hospital course.²⁵ Readmissions were defined as any inpatient admission within 30 days of discharge to any facility for which Medicare was charged.²⁶ This criterion has been applied in multiple previous studies using MedPAR to study readmission.^23,24

Covariates

Covariates included sex, age, comorbidities, year of surgery, surgical cohort (procedure), dual eligibility (having both Medicare and Medicaid coverage), unplanned admission, and hospital referral region (HRR). Dual eligibility serves as an individual-level indicator of socioeconomic status, and unplanned admission reflects severity of illness at the time of presentation.²⁷ Identification of comorbidities was limited to the first 10 diagnosis codes listed for the hospital admission as a way to mitigate the effects of upcoding by MA plans, although this risk is lowest for diagnoses coded during hospitalization.^28,29 Secular trends were accounted for by including the year of the operation as a categorical variable.

HRRs are available from CMS and are defined by where patients typically go for specialized or high-level care, meaning that hospitals within an HRR are connected through the movement of patients referred for complex treatments.³⁰ HRRs are related to MA penetration: Where there are robust health care networks and higher competition, MA plans tend to have higher penetration because they can offer better, more coordinated care options to beneficiaries. In areas with fewer health care resources, TM might be more appealing to beneficiaries, leading to lower MA penetration. This is important because very high or low penetration can cause “spillover” effects, leading to care being more similar between MA and TM beneficiaries due to practice patterns.^28,31 HRR was included as a way to account for this. We chose not to include hospital as a covariate because median patient cohorts within hospitals were small, and we anticipated that the hospital may serve as a mediator through which MA is influencing surgical outcomes via differences in referral networks and cost sharing compared with TM.

Analysis

The overall goal of this study was to compare differences in racial/ethnic disparities in surgical outcomes among MA beneficiaries vs those with TM. First, patient and hospital characteristics of Black, Hispanic, and White beneficiaries undergoing a surgical procedure who were enrolled in MA vs TM were compared using t and χ² tests (Table 1). Comorbidities were grouped into counts for descriptive purposes in the table.

To balance baseline patient characteristics and the probability of our race and ethnicity groups having MA coverage, inverse propensity score–weighting (IPSW) analysis was conducted. This has been described as a way to mitigate methodologic challenges comparing TM and MA populations due to selection effects, although all approaches have limitations.²⁸ Propensity scores were estimated using 3 separate logistic regression models (1 for each racial/ethnic group) with type of Medicare as the outcome and the previously listed covariates as predictors (excluding HRR).

The IPSW was derived from the PS and used to weight the entire study sample (eAppendix Table 2). Unadjusted results are presented in eAppendix Table 3. Multivariable logistic regression models adjusting for the covariates noted earlier were used to estimate interactions between type of Medicare insurance and race and ethnicity. Separate models were used to estimate Black-White and Hispanic-White differences. These models were used to produce marginal estimates of outcomes in each Medicare type–race/ethnicity subgroup. Contrasts were used to estimate racial and ethnic disparities within TM and MA separately and then to estimate differences in disparities between the 2 Medicare types. Difference and difference-in-disparities estimates are reported as weighted percentages and 95% CIs. All P values reported were 2-sided with an α of .05 as the threshold for significance. Statistical analyses were performed using Stata/MP 16.1 (StataCorp LLC).

RESULTS

Our sample included 1,603,887 Medicare beneficiaries, 564,076 (35.2%) of whom were enrolled in MA (Table 1). Most beneficiaries were White (85.6%), followed by Black (8.3%) and Hispanic (2.3%). Black (45.0%) and Hispanic (52.8%) beneficiaries were enrolled in MA at higher rates than White beneficiaries (33.6%). Overall, MA beneficiaries were more likely than TM beneficiaries to have at least 2 Elixhauser comorbidities (80.3% vs 78.5%; P < .001) and to have had unplanned operations (60.4% vs 58.6%; P < .001).

Differences in Disparities Between MA and TM

Mortality. Within TM, 6.2% of Black enrollees, 6.4% of Hispanic enrollees, and 6.3% of White enrollees died within 30 days, representing no significant disparities between groups (Black-White disparity: –0.11 percentage points [PP]; 95% CI, –0.31 to 0.08; P = .25; Hispanic-White disparity: 0.08 PP; 95% CI, –0.35 to 0.53; P = .71) (Table 2). Within MA, 5.7% of Black enrollees, 5.3% of Hispanic enrollees, and 6.1% of White enrollees died within 30 days, representing a Black-White disparity of –0.36 PP (95% CI, –0.57 to –0.15; P < .001) and a Hispanic-White disparity of –0.75 PP (95% CI, –1.14 to –0.36; P < .001) (Table 2). Thus, enrollment in MA vs TM was associated with no significant Black-White disparity (–0.24 PP; 95% CI, –0.51 to 0.02; P = .07) (Figure 1) and a 0.83-PP smaller Hispanic-White disparity (95% CI, –1.41 to –0.25; P = .01) in 30-day mortality (Figure 2).

Comparing in-hospital mortality, 3.5% of Black enrollees, 3.8% of Hispanic enrollees, and 3.4% of White enrollees in TM died in the hospital, representing no significant Black-White disparity (0.13 PP; 95% CI, –0.02 to 0.28; P = .08) and a 0.43-PP Hispanic-White disparity (95% CI, 0.09-0.77; P = .01). Within MA, 3.3% of Black enrollees, 3.1% of Hispanic enrollees, and 3.3% of White enrollees died in the hospital, representing no significant Black-White or Hispanic-White disparities (Black-White disparity: 0.03 PP; 95% CI, –0.13 to 0.19; P = .72; Hispanic-White disparity: –0.19 PP; 95% CI, –0.49 to 0.11; P = .21) (Table 2). Overall, enrollment in MA vs TM was associated with no significant difference in Black-White disparities (–0.10 PP; 95% CI, –0.31 to 0.10; P = .33) (Figure 1) and a 0.62-PP smaller Hispanic-White disparity (95% CI, –1.05 to –0.19; P = .01) for in-hospital mortality (Figure 2).

Complications. Among TM beneficiaries, 31.4% of Black enrollees, 28.6% of Hispanic enrollees, and 29.6% of White enrollees experienced a postoperative complication within 30 days (Black-White disparity: 1.82 PP; 95% CI, 1.45-2.20; P < .001; Hispanic-White: –1.06 PP; 95% CI, –1.73 to –0.40; P = .002). Within MA, 31.8% of Black enrollees, 27.3% of Hispanic enrollees, and 29.6% of White enrollees experienced a postoperative complication (Black-White disparity: 2.19 PP; 95% CI, 1.79-2.58; P < .001; Hispanic-White disparity: –2.30 PP; 95% CI, –2.98 to –1.62; P < .001) (Table 2). Enrollment in MA vs TM was associated with no significant difference in Black-White disparities (0.36 PP; 95% CI, –0.14 to 0.87; P = .16) (Figure 1) and a 1.24-PP smaller Hispanic-White disparity (95% CI, –2.16 to –0.32; P = .01) in postoperative complications (Figure 2).

Serious complications occurred for 16.5% of Black enrollees, 13.7% of Hispanic enrollees, and 14.6% of White enrollees in TM (Black-White disparity: 1.92 PP; 95% CI, 1.63-2.20; P < .001; Hispanic-White disparity: –0.84 PP; 95% CI, –1.36 to –0.31; P = .002). Within MA, 17.1% of Black enrollees, 13.0% of Hispanic enrollees, and 14.9% of White enrollees experienced a serious complication (Black-White disparity: 2.23 PP; 95% CI, 1.92-2.54; P < .001; Hispanic-White disparity: –1.88 PP; 95% CI, –2.39 to –1.36; P < .001) (Table 2). Thus, enrollment in MA vs TM was associated with no significant difference in Black-White disparities (0.31 PP; 95% CI, –0.06 to 0.69; P = .10) (Figure 1) and a 1.04-PP smaller Hispanic-White disparity (95% CI, –1.75 to –0.32; P = .004) in serious complications (Figure 2).

Readmissions. Within TM, 15.5% of Black enrollees, 13.6% of Hispanic enrollees, and 15.4% of White enrollees were readmitted within 30 days, resulting in no Black-White disparity (0.06 PP; 95% CI, –0.26 to 0.39; P = .70) and a –1.82-PP Hispanic-White difference favoring Hispanic individuals (95% CI, –2.41 to –1.23; P < .001). Within MA, 12.9% of Black enrollees, 11.6% of Hispanic enrollees, and 13.0% of White enrollees experienced a 30-day readmission, reflecting no significant Black-White disparity (–0.10 PP; 95% CI, –0.43 to 0.22; P = .53) and a similar –1.42-PP Hispanic-White difference favoring Hispanic individuals (95% CI, –1.95 to –0.88; P < .001) (Table 2). Therefore, enrollment in MA vs TM was associated with no significant difference in Black-White disparities (–0.17 PP; 95% CI, –0.60 to 0.26; P = .44) (Figure 1) or Hispanic-White disparities (0.41 PP; 95% CI, –0.38 to 1.20; P = .31) in postoperative readmissions (Figure 2).

DISCUSSION

This nationally representative study on differences in disparities between MA and TM has 3 main findings. First, enrollment in MA was associated with smaller Hispanic-White disparities in 30-day postoperative mortality. Second, MA enrollment was associated with smaller Hispanic-White disparities in postoperative complications and serious complications but no difference in Black-White disparities. Third, there were no differences in Black-White or Hispanic-White disparities in readmissions between MA and TM. These findings suggest that there are potential features of MA that narrow disparities in critical surgical outcomes. However, disparities were not uniformly or consistently narrowed.

Prior literature on how MA may impact disparities in mortality is limited, particularly for surgical populations. One study examining risk-adjusted overall mortality between MA and TM enrollees found that MA beneficiaries with low income or non-White race were less likely to die than would be predicted had those individuals been enrolled in traditional fee-for-service Medicare.³² However, this study included only 1 MA insurance provider. Our study adds to these findings, demonstrating that MA is associated with lower perioperative mortality for Black and Hispanic patients compared with White patients and that there were no differences between racial/ethnic groups in TM. Various aspects of MA plans may act as potential mechanisms of this lower disparity in mortality rates. For example, MA’s focus on care management may contribute to differences in postdischarge care coordination that may particularly benefit vulnerable patients.

Existing literature has yet to evaluate potential differences in disparities in postoperative complications between MA and TM. In the present study, Hispanic beneficiaries had lower postoperative complications and serious complications than White patients in both MA and TM. This could be related to the Hispanic paradox: the finding of better health outcomes in certain cases in Hispanic patients compared with non-Hispanic White patients, despite lower socioeconomic status and higher comorbidities.³³ However, surgical literature has not consistently found this to be true related to postoperative complications.^34,35 MA’s apparent benefit for Hispanic-White disparities is related to better outcomes of Hispanic individuals in MA compared with White individuals, who have more similar outcomes between MA and TM. One possible explanation for this is that healthier Hispanic beneficiaries may be preferentially enrolling in or accessing surgery via MA. However, there is evidence that MA beneficiaries undergo surgery at hospitals with fewer postoperative safety events, indicating plan features may play a role as well (ie, greater discretion by the health plan in approving patients for elective surgery and selecting hospitals for surgical patients).³⁶ In contrast, Black beneficiaries had higher rates of postoperative complications compared with White beneficiaries, and these disparities were not mitigated by MA vs TM enrollment.

Results of prior work evaluating disparities in readmission rates between MA and TM have been mixed. One study of racial disparities in 30-day readmission rates for MA beneficiaries undergoing 1 of 6 major surgeries found that MA was associated with almost double the racial disparity in readmission rates compared with TM.¹³ Alternatively, a study by the same group examining medical admissions found that MA was associated with a decreased racial disparity in readmission rates.³⁷ This suggests that MA and TM may differentially impact disparities in surgical and medical conditions.³⁷ These studies, however, were single state and used data now more than a decade old, when MA enrollment and beneficiary composition differed from present day. Our findings within a contemporary national cohort contrast these prior findings, demonstrating no difference in readmission disparities between MA and TM. MA’s features such as utilization management may be effective at reducing readmissions across all groups without impacting disparities.³⁸

Policy Implications

Our findings have several important policy implications. First, future research should try to elucidate the mechanisms underlying our findings, such as whether MA’s care management features, lower cost sharing, or supplemental benefits (eg, home health care services) may better support vulnerable patients undergoing surgery. This would allow beneficial features to be utilized more intentionally across MA plans and to potentially improve aspects of TM. Consideration should also be given to whether these findings point toward unobserved favorable selection bias for healthier ethnic minority older adults in MA compared with TM (more so than for White beneficiaries). This possibility is supported by literature indicating that MA disproportionately disenrolls low-income, disabled, high-cost, and racial/ethnic minority beneficiaries.^4,16,39-41 Policy changes have demonstrated improvement in favorable selection bias over time, but more effort may be needed to understand and address how this may still be disproportionately happening with racial/ethnic minority beneficiaries.⁴²

Additionally, further attention is needed to examine and identify whether MA is associated with differences in racial/ethnic disparities compared with TM across a range of conditions and services. Medical and other health care services administered via MA may have different findings than surgical populations. Lastly, the CMS Office of Minority Health has emphasized the need for measuring and reporting quality information stratified by race/ethnicity to identify and mitigate health disparities.⁴³ This study demonstrates the need to do this to evaluate surgical quality and ultimately use this insight to incentivize MA plans to prioritize and improve disparities in care among their enrollees.

Limitations

Our study has several limitations. First, claims data may lack the clinical granularity needed to capture potential confounding factors influencing our outcomes. To mitigate this potential risk, we chose outcomes that have been well validated in claims data sets through the Complications Screening Program and are least susceptible to this bias.^44,45 Second, in comparing MA and TM, there is the potential for unmeasured differences in the factors driving beneficiary coverage choice, health outcomes once enrolled, provider networks, and plan design across MA plans. Although we could not evaluate all these factors, utilizing our IPSW methodology, adjusting for HRR, and minimizing the potential impact of upcoding comorbidities are strategies to improve the fidelity of comparing these populations.²⁸ Third, our results were limited to 4 general surgery procedures and may not be generalizable to a broader range of operations. However, these represent some of the most commonly performed operations and have been previously used to evaluate Medicare policy.^18,46 Lastly, as previously mentioned, our data likely undercount Hispanic ethnicity. More recent updates to Medicare data are improving the accuracy of the race/ethnicity variable, which will be important for future studies using claims data.

CONCLUSIONS

In this nationally representative study of Medicare beneficiaries undergoing surgery, MA enrollment was associated with smaller Hispanic-White disparities in postoperative 30-day mortality and complications and no significant differences in Black-White or readmission disparities. These findings indicate there are potential features of MA that preferentially benefit racial and ethnic minority beneficiaries but not uniformly. Future work should examine potential mechanisms of MA that could drive lower postoperative mortality and complications for racial/ethnic minority older adults. 

Author Affiliations: Department of Surgery, The University of Texas Southwestern Medical Center (EEI), Dallas, TX; National Clinician Scholars Program, Institute for Healthcare Policy and Innovation, University of Michigan (EEI), Ann Arbor, MI; Center for Health Outcomes and Policy (EEI, NK, AMI), Department of Surgery (EEI, NK, AMI), and Division of General Medicine, Department of Internal Medicine (RT), University of Michigan Medical School, Ann Arbor, MI.

Source of Funding: None.

Author Disclosures: Dr Isenberg is supported by the US Department of Veterans Affairs (VA) Office of Academic Affiliations through the VA/National Clinician Scholars Program and receives funding from Blue Cross Blue Shield of Michigan Foundation unrelated to this work. Mr Kunnath reports National Institutes of Health (NIH) grant funding to his institution. Dr Ibrahim is a member of the AcademyHealth board and has received grants from the Agency for Healthcare Research and Quality (AHRQ) and NIH unrelated to this work. Dr Tipirneni is an unpaid board member for Center for Health and Research Transformation and has received funding from AHRQ, Blue Cross Blue Shield of Michigan, National Institute on Aging, National Institute of Allergy and Infectious Diseases, and National Institute on Minority Health and Health Disparities unrelated to this work.

Authorship Information: Concept and design (EEI, NK, AMI, RT); acquisition of data (NK, AMI); analysis and interpretation of data (EEI, NK, RT); drafting of the manuscript (EEI); critical revision of the manuscript for important intellectual content (EEI, AMI, RT); statistical analysis (NK); and supervision (RT).

Address Correspondence to: Erin E. Isenberg, MD, MSc, University of Michigan, 2800 Plymouth Rd, North Campus Research Complex Bldg 16, Ann Arbor, MI 48109. Email: isenbere@med.umich.edu.

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