Association of Medicare Advantage vs Traditional Medicare With 30-Day Mortality Among Patients With Acute Myocardial Infarction

Abstract

Importance: Medicare Advantage health plans covered 37% of beneficiaries in 2018, and coverage increased to 48% in 2022. Whether Medicare Advantage plans provide similar care for patients presenting with specific clinical conditions is unknown.

Objective: To compare 30-day mortality and treatment for Medicare Advantage and traditional Medicare patients presenting with acute myocardial infarction (MI) from 2009 to 2018.

Design, setting, and participants: Retrospective cohort study that included 557 309 participants with ST-segment elevation [acute] MI (STEMI) and 1 670 193 with non-ST-segment elevation [acute] MI (NSTEMI) presenting to US hospitals from 2009-2018 (date of final follow up, December 31, 2019).

Exposures: Enrollment in Medicare Advantage vs traditional Medicare.

Main outcomes and measures: The primary outcome was adjusted 30-day mortality. Secondary outcomes included age- and sex-adjusted rates of procedure use (catheterization, revascularization), postdischarge medication prescriptions and adherence, and measures of health system performance (intensive care unit [ICU] admission and 30-day readmissions).

Results: The study included a total of 2 227 502 participants, and the mean age in 2018 ranged from 76.9 years (Medicare Advantage STEMI) to 79.3 years (traditional Medicare NSTEMI), with similar proportions of female patients in Medicare Advantage and traditional Medicare (41.4% vs 41.9% for STEMI in 2018). Enrollment in Medicare Advantage vs traditional Medicare was associated with significantly lower adjusted 30-day mortality rates in 2009 (19.1% vs 20.6% for STEMI; difference, -1.5 percentage points [95% CI, -2.2 to -0.7] and 12.0% vs 12.5% for NSTEMI; difference, -0.5 percentage points [95% CI, -0.9% to -0.1%]). By 2018, mortality had declined in all groups, and there were no longer statically significant differences between Medicare Advantage (17.7%) and traditional Medicare (17.8%) for STEMI (difference, 0.0 percentage points [95% CI, -0.7 to 0.6]) or between Medicare Advantage (10.9%) and traditional Medicare (11.1%) for NSTEMI (difference, -0.2 percentage points [95% CI, -0.4 to 0.1]). By 2018, there was no statistically significant difference in standardized 90-day revascularization rates between Medicare Advantage and traditional Medicare. Rates of guideline-recommended medication prescriptions were significantly higher in Medicare Advantage (91.7%) vs traditional Medicare patients (89.0%) who received a statin prescription (difference, 2.7 percentage points [95% CI, 1.2 to 4.2] for 2018 STEMI). Medicare Advantage patients were significantly less likely to be admitted to an ICU than traditional Medicare patients (for 2018 STEMI, 50.3% vs 51.2%; difference, -0.9 percentage points [95% CI, -1.8 to 0.0]) and significantly more likely to be discharged to home rather than to a postacute facility (for 2018 STEMI, 71.5% vs 70.2%; difference, 1.3 percentage points [95% CI, 0.5 to 2.1]). Adjusted 30-day readmission rates were consistently lower in Medicare Advantage than in traditional Medicare (for 2009 STEMI, 13.8% vs 15.2%; difference, -1.3 percentage points [95% CI, -2.0 to -0.6]; and for 2018 STEMI, 11.2% vs 11.9%; difference, 0.6 percentage points [95% CI, -1.5 to 0.0]).

Conclusions and relevance: Among Medicare beneficiaries with acute MI, enrollment in Medicare Advantage, compared with traditional Medicare, was significantly associated with modestly lower rates of 30-day mortality in 2009, and the difference was no longer statistically significant by 2018. These findings, considered with other outcomes, may provide insight into differences in treatment and outcomes by Medicare insurance type.

Figure 1.. Thirty-Day Mortality Rate: 2009 and 2018^a

^aSample sizes are reported in the Table. ^bIndicates % difference of Medicare Advantage minus traditional Medicare. STEMI indicates ST-segment elevation myocardial infarction; NSTEMI, non–ST-segment elevation myocardial infarction.

Figure 2.. Procedure Rates and Hospital Utilization: 2009 and 2018^a

^aSample sizes are reported in the Table. ^bData are standardized by sex and age. Numeric values indicate % of patient utilization for all metrics except length of stay, which is reported as mean length of stay, number of days. ^cIndicates % difference of Medicare Advantage minus traditional Medicare for all metrics except length of stay, which is reported as difference in mean length of stay, number of days. For exact difference (95% CI) values, see the section Inpatient and 90-Day Procedures and Resource Use. STEMI indicates ST-segment elevation myocardial infarction; NSTEMI, non–ST-segment elevation myocardial infarction; PCI, percutaneous coronary intervention; CABG, coronary artery bypass grafting; ICU, intensive care unit.

Figure 3.. Postdischarge Prescription Drug Utilization and Adherence: 2009 and 2018^a

^aSample sizes are reported in the Table. ^bData are standardized by sex and age. ^cIndicates % difference of Medicare Advantage minus traditional Medicare. STEMI indicates ST-segment elevation myocardial infarction; NSTEMI, non–ST-segment elevation myocardial infarction; ACE, angiotensin-converting enzyme; ARB, angiotensin receptor blocker.

Figure 4.. Hospital-Level Concentration of Acute MI Admissions by MI and Medicare Type (Herfindahl-Hirschman Index): 2009-2018

County-level measures of the Herfindahl-Hirschman Index (HHI) were constructed by summing the squared market share of ST-segment elevation myocardial infarction (STEMI) or non–ST-segment elevation myocardial infarction (NSTEMI) hospital admissions for hospitals serving patients from each county with patients enrolled in Medicare Advantage or traditional Medicare. The mean of the county-level HHI was weighted by the Medicare Advantage enrollment in the county. Index range, 0 to 10 000, with 10 000 representing a market with only 1 hospital. A market is considered concentrated if its HHI is greater than 2500 and super concentrated if greater than 5000.