# The Immune‐Autonomic Interface in Aging: Baseline Immune Profile Shapes Cardiac Autonomic Response to Exercise

## TL;DR

This study shows that the immune system's baseline state influences how the heart responds to exercise in older adults, highlighting immune-autonomic interactions in aging.

## Contribution

The study reveals how baseline immune profiles dynamically shape cardiac autonomic responses to acute exercise in older adults.

## Key findings

- Baseline immune cell subsets like B-cells and T-cells are linked to HRV changes during exercise and recovery.
- Bayesian models show immune profiles predict the magnitude and direction of HRV shifts during exercise.
- The immune-autonomic interface contributes to heterogeneity in physiological resilience among older adults.

## Abstract

Aging is characterized by reduced physiological resilience, linked to declines in both cardiac autonomic control (assessed via Heart Rate Variability, HRV) and immune function (immunosenescence, inflammaging). While static immune‐autonomic links are known, how baseline immune status dynamically influences autonomic responses to acute stress in aging remains unclear. This study investigated the association between baseline immune cell profiles and dynamic HRV changes during rest, acute exercise, and recovery in older adults. We quantified baseline lymphocyte subsets and assessed HRV during an exercise test. Using Bayesian mixed‐effects models, we found that while exercise significantly altered HRV as expected, baseline levels of specific immune cell subsets (e.g., B‐cells, T‐cells, CD4+/CD8+ ratio, and NK cells) were significantly associated with the pattern and magnitude of exercise‐induced HRV changes. This indicates that the pre‐existing immune state modulates the dynamic cardiac autonomic response to stress. Our findings highlight the critical role of immune‐autonomic crosstalk in shaping physiological resilience in aging, offering insights into heterogeneity in exercise responses and suggesting potential avenues for personalized health strategies.

In 83 older adults, baseline lymphocyte phenotypes quantified by flow cytometry predicted the magnitude and direction of HRV shifts during a 2‐min step test and recovery. Bayesian models show that the immune landscape shapes exercise autonomic trajectories in a domain‐specific manner, revealing heterogeneity in physiological resilience.