History of COVID-19 and Overall Survival Among Medicare Beneficiaries Hospitalized with Acute Ischemic Stroke, Medicare Cohort 2020-2021

Research Article

Austin J Cardiovasc Dis Atherosclerosis. 2024; 11(1): 1061.

History of COVID-19 and Overall Survival Among Medicare Beneficiaries Hospitalized with Acute Ischemic Stroke, Medicare Cohort 2020-2021

Tong X*; Yang Q; Gillespie C; Merritt RK

Division for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, USA

*Corresponding author: Tong X Division for Heart Disease and Stroke Prevention, Centers for Disease Control and Prevention, 4770 Buford Hwy, MS – S107-1, Atlanta, GA 30341, USA. Tel: 770-488-4551; Fax: 770-488-8334 Email: xtong@cdc.gov

Received: January 17, 2024 Accepted: February 27, 2024 Published: March 05, 2024

Abstract

Background: COVID-19 is associated with increased risk of Acute Ischemic Stroke (AIS). The present study examined the impact of prior COVID-19 diagnoses on overall survival among older AIS patients.

Methods: We included 250,079 Medicare Fee-For-Service (FFS) beneficiaries aged =65 years with AIS hospitalizations from 04/01/2020 through 12/31/2021. Overall survival was defined as the time from date of AIS hospitalization to date of death, or through end of follow-up on 03/31/2023. We used a Cox proportional hazard model to examine the association between history of COVID-19 and overall survival among AIS beneficiaries, and we obtained age, sex, race/ethnicity, Social Vulnerability Index (SVI), National Institutes of Health Stroke Scale score, and comorbidity-adjusted survival estimates.

Results: Among 250,079 Medicare FFS beneficiaries with AIS, 98,327 (39.3%) died during a median of 590 days (IQR, 169–819 days) of follow-up with a total of 365,606 person-years. The 1-year adjusted overall survival was 62.0%, 67.4%, and 68.8% in beneficiaries with hospitalized COVID-19, with non-hospitalized COVID-19 and no COVID-19 respectively (p<0.001). Compared to AIS without history of COVID-19, the adjusted mortality hazard ratios were 1.30 (95% CI, 1.26–1.34) and 1.06 (95% CI, 1.03–1.10) for those with a history of hospitalized and non-hospitalized COVID-19, respectively. The patterns of overall survival by COVID-19 history were largely consistent across age groups, sex, race/ethnicity, and SVI groups.

Conclusions: A history of COVID-19 diagnoses, especially with a history of severe COVID-19, was associated with a significantly higher risk of all-cause mortality among Medicare FFS beneficiaries hospitalized with AIS.

Keywords: Acute ischemic stroke; Hospitalizations; Survival; COVID-19

Introduction

Stroke is the fifth leading cause of death and a leading cause of long-term disability in the United States (U.S.) [1]. Recent studies suggested that COVID-19 diagnosis is associated with increased risk of Acute Ischemic Stroke (AIS), especially shortly after exposure [2]. Patients with ischemic stroke and concurrent COVID-19 had worse outcomes compared to those without COVID-19 [3]. However, few studies have examined the effects of prior COVID-19 diagnosis on overall survival among older U.S. adults hospitalized with AIS.

This study aimed to assess the overall survival among older AIS Medicare beneficiaries with a history of COVID-19 diagnoses, especially among those with severe COVID-19, as compared to those without a history of COVID-19.

Materials and Methods

We used the real-time Medicare monthly files to identify Medicare Fee-For-Service (FFS) beneficiaries aged 65 years or older, hospitalized with AIS from 04/01/2020 through 12/31/2021. AIS was defined as having a hospital admission with primary diagnosis of International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) code I63. If beneficiaries had more than one date of AIS hospitalization during the study period, the first hospitalization date was chosen. We obtained the first diagnosis of COVID-19 from Medicare Part A (inpatient claims) and Part B (physician’s office claims) using ICD-10-CM code U07.1. We identified AIS beneficiaries as having a history of COVID-19 when the first COVID-19 diagnoses date was earlier than the AIS admission date; those with a history of COVID-19 were classified by hospitalization status to reflect severity. We used National Institutes of Health Stroke Scale (NIHSS) scores (ICD-10-CM code: R29.7) to assess stroke severity. We incorporated the Social Vulnerability Index (SVI) by counties published in 2020 by the US Centers for Disease Control and Prevention (CDC) [4]. The final analytical study population had 250,079 Medicare FFS beneficiaries diagnosed with AIS.

We calculated the median (Interquartile Range, IQR) and mean (Standard Error, SE) of age, SVI, and the time between the first COVID-19 diagnosis and AIS hospitalization. We calculated the percentage distribution of age group, sex, race/ ethnicity, NIHSS groups (0–9, 10–19, 20–29, 30+), SVI groups (low 0–0.33, moderate 0.34–0.66, high 0.67–1.0), the percent of deaths during follow-up, and the medical history of comorbidities at baseline, among AIS beneficiaries by status of COVID-19 history: with hospitalized COVID-19; non-hospitalized COVID-19; and no COVID-19 diagnoses. The comorbidities assessed included: history of stroke or Transient Ischemic Attack (TIA), ischemic heart disease, hypertension, hypercholesterolemia, diabetes, atrial fibrillation, heart failure, chronic kidney disease, acute myocardial infarction, peripheral vascular disease, chronic obstructive pulmonary disease, and tobacco use. These comorbidities were based on the Chronic Conditions Warehouse definitions from Centers for Medicare and Medicaid Services [5]. About 37% of AIS beneficiaries had missing NIHSS scores, and we used multiple imputation to impute the missing values with 25 imputed datasets using PROC MI in SAS (SAS Institute).

We defined the survival time as the number of days from the date of AIS hospitalization to the date of death or end of follow-up (03/31/2023), whichever came first. We performed the survival and subgroup analyses by age groups (66–74 years, 75–84 years and =85 years), sex, race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, and others [non-Hispanic other races], and SVI (low, moderate, high). We estimated the mean (SE) survival time and used the log-rank test to compare overall survival among AIS beneficiaries by COVID-19 history status. We performed Cox proportional hazards regression analyses to examine the association between COVID-19 history status and mortality adjusting for age, sex, race/ethnicity, NIHSS scores, SVI, and comorbidities. To assess the proportional hazard assumption, we examined log-log plots and Schoenfeld residuals. To better understand the absolute differences in survival, we estimated 1-year adjusted overall survival by COVID-19 status. SAS, version 9.4 was used for the analyses, and a two-sided p-value of <0.05 was considered statistically significant.

This study uses de-identified claims data that are exempt from IRB review, was reviewed by Centers for Disease Control and Prevention (CDC), and conducted by adhering to applicable federal law, CDC policy, and the CDC-CMS Interagency agreement and data use agreement.

Results

There were 250,079 Medicare FFS beneficiaries hospitalized with AIS as the primary diagnosis between 04/01/2020, and 03/31/2021. Among them, 98,327 (39.3%) died during a median follow-up of 590 days (IQR: 169–819), with a total of 365,606 person-years (Table 1).