Medicare Shared Savings Program and readmission rate among ischemic stroke patients

Objective

Hospitals participating in the Medicare Shared Savings Program (MSSP) share with the Centers for Medicare and Medicaid Services (CMS) the savings generated by reducing readmissions. Our aim was to determine whether MSSP is associated with changes in readmissions and mortality for Medicare patients hospitalized with ischemic stroke, and whether MSSP has a different impact on safety-net hospitals (SNHs) compared to non-SNHs.   

Methods

This study was based on the CMS Hospital Compare data for risk-standardized 30-day readmission and mortality rates for Medicare patients hospitalized with ischemic strokes between 2010 and 2017. With propensity score matched sample, hospital-level difference-in-difference (DID) analysis was used to determine whether MSSP was associated with changes in hospital readmission and mortality as well as to examine the impact of MSSP on SNHs compared to non-SNHs. 

Results

MSSP-participating hospitals had slightly greater reductions in readmission rates compared to matched non-participating hospitals (difference, 0.25 percentage points; 95% CI: -0.42, -0.08). Mortality rates decreased among all hospitals, but mortality reduction was not significantly different between MSSP-participating hospitals and matched hospitals (difference, 0.06 percentage points; 95% CI: -0.28, 0.17). Prior to MSSP, readmission rates in SNHs were higher compared to non-SNH, but MSSP did not have a significantly different impact on hospital readmission and mortality rates for SNH and non-SNHs.

Conclusion

MSSP led to slightly fewer readmissions without increases in mortality in patients hospitalized with ischemic stroke. Similar reductions in readmission rates were observed in SNHs and non-SNHs participating in MSSP, indicating persistent gaps between SNHs and non-SNHs.

## 研究目标
参与医疗保险共享储蓄计划（Medicare Shared Savings Program, MSSP）的医院需向医疗保险与医疗救助服务中心（Centers for Medicare and Medicaid Services, CMS）呈报因降低患者再入院率所产生的医疗费用节约额。本研究旨在明确两个核心问题：其一，MSSP是否与因缺血性脑卒中住院的医保患者的再入院率及死亡率变化存在关联；其二，相较于非安全网医院，MSSP对安全网医院（safety-net hospitals, SNHs）的影响是否存在差异。

## 研究方法
本研究的数据来源于2010至2017年间的CMS医院比较数据集（CMS Hospital Compare），该数据集包含因缺血性脑卒中住院的医保患者的风险标准化30天再入院率与死亡率。本研究采用倾向得分匹配样本，并通过医院层面双重差分（difference-in-difference, DID）分析，以检验MSSP与医院再入院率、死亡率变化的关联，同时对比分析MSSP对安全网医院与非安全网医院的影响差异。

## 研究结果
相较于匹配的非参与医院，参与MSSP的医院再入院率降幅略高（组间差异为0.25个百分点；95%置信区间：-0.42, -0.08）。所有医院的患者死亡率均有所下降，但参与MSSP的医院与匹配对照组医院的死亡率降幅无显著统计学差异（组间差异为0.06个百分点；95%置信区间：-0.28, 0.17）。在MSSP实施前，安全网医院的再入院率高于非安全网医院，但MSSP对安全网医院与非安全网医院的再入院率及死亡率的影响并无显著差异。

## 研究结论
MSSP可使因缺血性脑卒中住院的医保患者再入院率略有降低，且未导致患者死亡率升高。参与MSSP的安全网医院与非安全网医院的再入院率降幅相近，这表明两类医院之间仍存在持续的绩效差距。