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

Exercise significantly altered Heart Rate Variability (HRV) in older adults as expected during an incremental exercise test.

• HRV was assessed during rest, acute exercise, and recovery phases.
• An exercise test protocol was used to induce acute physiological stress.
• Bayesian mixed-effects models were used to analyze dynamic HRV changes across the three phases.
• The exercise-induced HRV changes served as the primary outcome variable for examining immune-autonomic interactions.

Baseline B-cell levels were significantly associated with the pattern and magnitude of exercise-induced HRV changes in older adults.

• Baseline lymphocyte subsets were quantified prior to the exercise test.
• Bayesian mixed-effects models identified B-cells as a significant predictor of dynamic HRV response.
• The association was observed across the rest, exercise, and recovery phases.
• This finding suggests B-cells contribute to immune-autonomic crosstalk during acute stress.

Baseline T-cell levels were significantly associated with the dynamic cardiac autonomic response to acute exercise stress.

• T-cell subsets were quantified at baseline as part of lymphocyte profiling.
• Bayesian mixed-effects models identified T-cells as a significant predictor of HRV changes during and after exercise.
• The association highlights the role of adaptive immune cells in modulating autonomic function.
• Results were interpreted in the context of immunosenescence affecting older adult physiology.

The CD4+/CD8+ T-cell ratio at baseline was significantly associated with exercise-induced HRV changes in older adults.

• The CD4+/CD8+ ratio is a marker commonly used to assess immune aging and immunosenescence.
• Bayesian mixed-effects models identified the CD4+/CD8+ ratio as a significant predictor of autonomic response patterns.
• This finding links a known immunosenescence marker to cardiac autonomic regulation under acute stress.
• The association was present across the dynamic phases of rest, exercise, and recovery.

Baseline NK cell levels were significantly associated with the pattern and magnitude of exercise-induced HRV changes.

• Natural Killer (NK) cells were quantified as part of the baseline lymphocyte subset panel.
• Bayesian mixed-effects models revealed NK cell counts as a significant predictor of dynamic HRV response.
• NK cells are known to be altered with aging, linking innate immune status to autonomic regulation.
• This finding extends the immune-autonomic interface beyond adaptive immune cells to innate immune populations.

The pre-existing immune state modulates the dynamic cardiac autonomic response to stress in older adults, demonstrating an immune-autonomic interface in aging.

• The study used Bayesian mixed-effects models to analyze associations between baseline immune profiles and HRV dynamics.
• Multiple lymphocyte subsets (B-cells, T-cells, CD4+/CD8+ ratio, NK cells) were independently associated with autonomic response.
• The findings indicate that immunosenescence and inflammaging contribute to heterogeneity in exercise autonomic responses.
• Results suggest that static immune-autonomic links extend to dynamic stress-response contexts.
• The authors propose these findings offer 'insights into heterogeneity in exercise responses and suggesting potential avenues for personalized health strategies.'

Aging is associated with concurrent declines in cardiac autonomic control and immune function, forming the biological basis for immune-autonomic crosstalk.

• Cardiac autonomic control was assessed via Heart Rate Variability (HRV).
• Immune aging was characterized by immunosenescence and inflammaging.
• The study population consisted of older adults.
• Prior research had established static immune-autonomic links, but dynamic associations during acute stress were previously unclear.