b"Figure 1. Dose-response relationship between PM 2.5and Ozone levels from control day to case day and risk of OHCA on a continuous scale. (Results are adjusted for temperature). Figure used with permission of Elsevier from Malik A et al. Association of ambient air pollution with risk of out of hospital cardiac arrest in the United States. AHJ Plus: Cardiology Research and Practice. 17: 100151 (2022). Permission conveyed through Copyright Clearance Center Inc.Medicare Data Linkage Numerous registries have reported on layperson response and outcomes for OHCA, but data on long-term survival, hospital readmission, and costs for arrest survivors are limited. To examine this, CARES data were linked to data from Medicare, the largest insurer in the United States (fee-for-service Medicare) using probabilistic matching algorithms. The identifiers used included patient age and sex, admission date, admitting hospital, and a qualifying International Classification of Diseases, Ninth Revision or Tenth Revision, Clinical Modification diagnosis or procedure code. Analysis of the linked dataset found that for older individuals who had survived their cardiac arrest, approximately one out of three died within the first year following the arrest, and readmissions were common. Figure 2 represents Kaplan-Meier estimates for 5-year survival among those discharged alive from an out-of-hospital cardiac arrest for the overall cohort (A) and by discharge destination (B). Following hospital discharge, the mortality rate was initially high (27.0% at 3 months) and rose gradually over time. The estimated mortality rate at one and three years after discharge were 37.1% and 50.1%, respectively. During the first year, 40.1% of patients were readmitted to the hospital at least once, with 19.7% readmitted on more than one occasion. The linked dataset utilized in the study offers a unique opportunity to gain insights into the long-term outcomes of OHCA survivors, which is not readily available within the CARES dataset.Data linkage also allows for validation across datasets. Using the CARES-Medicare dataset, researchers examined the concordance of race/ethnicity in CARES with self-reported race/ethnicity in Medicare (Table 2). TheFigure 2. Long-term survival among those concordance rate for race/ethnicity between CARES and Medicare was highsurviving to hospital discharge in Cardiac for non-Hispanic White patients (93.4%), followed by non-Hispanic BlackArrest Registry to Enhance Survival: patients (89.1%). However, the concordance rate was slightly lower for otherMortality, Events, and Costs for Cardiac ethnic groups 74.6% for Hispanics, 69.6% for Asians and Pacific Islanders,Arrest survivors from 2013 to 2019.and 37.8% for American Indian or Alaskan Natives. For patients with unknownFigure used with permission of Wolters Kluwer Health, Inc. race/ethnicity in CARES, the majority (69.0%) identified themselves as non- from Chan PS et al. Long-Term Outcomes for Out-of-Hospital Cardiac Arrest in Elderly Patients: An Analysis of Cardiac Hispanic White in Medicare, while a smaller percentage self-reported as non- Arrest Registry to Enhance Survival Data Linked to Medicare Hispanic Black (10.7%), Hispanic (7.4%), Asian or Pacific Islander (8.5%), andFiles. Circ Cardiovasc Qual Outcomes. 15(10):e009042 (2022). Permission conveyed through Copyright Clearance American Indian or Alaskan Native (0.9%). These findings indicate that EMSCenter Inc.personnel were accurately identifying the race and ethnicity of OHCA victims as per patients' self-reported information. 45"