The Immune-Autonomic Interface in Aging: Baseline Immune Profile Shapes Cardiac Autonomic Response to Exercise.

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.