# Age–Treatment Interactions in Out-of-Hospital Cardiac Arrest: A Nationwide Registry Analysis

## TL;DR

This study examines how age affects survival after cardiac arrest and finds that treatment benefits still exist for elderly patients.

## Contribution

The study identifies age-treatment interactions and develops a predictive model for OHCA survival using nationwide EMS data.

## Key findings

- Elderly OHCA patients had lower survival rates compared to non-elderly patients.
- VF/VT, medical witness, and AED shock were the strongest predictors of survival.
- Age reduced the survival benefit of VF/VT and the protective effect of female sex.

## Abstract

Introduction: Population aging in Europe is ongoing and linked to poorer outcomes after out-of-hospital cardiac arrest (OHCA), yet age alone should not guide treatment. We aimed to describe age-related survival, identify independent predictors, and develop a predictive model using EMS data. Methods: We analyzed 147,962 adult OHCA cases from the Hungarian National EMS registry. Variables included initial rhythm, witness status, location, and sex. The primary outcome was survival to hospital admission. Multivariable logistic regression assessed independent predictors and age × treatment interactions; performance was evaluated with AUC, Brier score, and cross-validation. Results: Overall survival was 8.8%; elderly patients had lower survival (7.3%) than non-elderly (11.7%, p < 0.001). VF/VT (adjusted OR 5.34), medical personnel witness (OR 4.52), and AED shock (OR 3.52) were the strongest predictors. Age attenuated the survival benefit of VF/VT (interaction OR 0.914) and the protective effect of female sex (interaction OR 0.882; both p < 0.001). Model performance was good (AUC 0.784; Brier 0.0705). Conclusions: Age independently predicts survival after OHCA, but substantial treatment benefits persist in the elderly. Age–treatment interactions support geriatric-tailored resuscitation strategies and potential integration of this high-performing model into clinical decision support systems.