The Medicare Shared Savings Program and Outcomes for Ischemic Stroke Patients: a Retrospective Cohort Study

Abstract

Background: Post-stroke care delivery may be affected by provider participation in Medicare Shared Savings Program (MSSP) Accountable Care Organizations (ACOs) through systematic changes to discharge planning, care coordination, and transitional care.

Objective: To evaluate the association of MSSP with patient outcomes in the year following hospitalization for ischemic stroke.

Design: Retrospective cohort SETTING: Get With The Guidelines (GWTG)-Stroke (2010-2014) PARTICIPANTS: Hospitalizations for mild to moderate incident ischemic stroke were linked with Medicare claims for fee-for-service beneficiaries ≥ 65 years (N = 251,605).

Main measures: Outcomes included discharge to home, 30-day all-cause readmission, length of index hospital stay, days in the community (home-time) at 1 year, and 1-year recurrent stroke and mortality. A difference-in-differences design was used to compare outcomes before and after hospital MSSP implementation for patients (1) discharged from hospitals that chose to participate versus not participate in MSSP or (2) assigned to an MSSP ACO versus not or both. Unique estimates for 2013 and 2014 ACOs were generated.

Key results: For hospitals joining MSSP in 2013 or 2014, the probability of discharge to home decreased by 2.57 (95% confidence intervals (CI) = - 4.43, - 0.71) percentage points (pp) and 1.84 pp (CI = - 3.31, - 0.37), respectively, among beneficiaries not assigned to an MSSP ACO. Among discharges from hospitals joining MSSP in 2013, beneficiary ACO alignment versus not was associated with increased home discharge, reduced length of stay, and increased home-time. For patients discharged from hospitals joining MSSP in 2014, ACO alignment was not associated with changes in utilization. No association between MSSP and recurrent stroke or mortality was observed.

Conclusions: Among patients with mild to moderate ischemic stroke, meaningful reductions in acute care utilization were observed only for ACO-aligned beneficiaries who were also discharged from a hospital initiating MSSP in 2013. Only 1 year of data was available for the 2014 MSSP cohort, and these early results suggest further study is warranted.

Registration: None.

Keywords: Medicare; health policy; health services research; outcomes; stroke; utilization.

Figure 1.

Trends in patient outcomes by hospital MSSP ACO implementation year (with 95% CI). MSSP, Medicare Shared Savings Program; CI, 95% confidence interval. Days in the community was calculated as days alive and not in an inpatient or skilled nursing facility. Adjusted models controlled for patient demographics, health status at discharge, medical history, hospital factors, county factors, no evaluation and management visit the year prior to incident stroke and fixed effects for hospital referral region, and year/month of admission.

Figure 2.

Difference-in-differences estimates for MSSP versus non-MSSP hospitals and estimates for the association of ACO-aligned beneficiaries with outcomes (with 95% CI). CI, 95% confidence intervals. Days in the community is defined as days not in an inpatient or skilled nursing facility. All models were adjusted for patient demographics, health status at discharge, medical history, hospital factors, county factors, no evaluation and management visit the year prior to incident stroke and fixed effects for Hospital Referral Region, and year/month of admission.

Figure 3.

Average marginal effects for beneficiary ACO alignment versus not aligned by hospital MSSP implementation year.

Figure 4.

Estimates for potential moderators of the relationship between MSSP hospital status and home-time with 95% confidence intervals.*Value > 75th vs. ≤ 75th percentile. PCP, primary care physician. Care continuity (binary) is non-zero when the beneficiary is aligned with the same ACO providing acute stroke care during hospitalization. MSSP market penetration (continuous) is the proportion of hospital discharges where the beneficiary is aligned with any MSSP ACO. Area deprivation and PCP supply are county-level factors from the Area Deprivation Index and Area Health Resource File respectively.