From brain to heart: cognitive performance shapes exercise- induced cardiac autonomic trajectories in older adults

Background: Autonomic dysregulation and cognitive decline often co-occur in aging, but most work uses only resting heart rate variability (HRV). Therefore, we examined whether global cognitive performance modulates dynamic HRV responses to a functional exercise test in community-dwelling older adults. Methods: In this cross-sectional study, 104 adults aged 60-85 years from southern Chile completed a rest-exercise-recovery protocol using the 2-Min Step Test. Global cognition was assessed with the Addenbrooke's Cognitive Examination. Short-term HRV (time and frequency domains), parasympathetic (PNS) and sympathetic (SNS) indices, and Baevsky's Stress Index were derived from Polar H10 recordings at rest, during exercise, and recovery. Hierarchical Bayesian regression models characterized HRV trajectories as a function of cognitive performance, adjusting for body mass index. Results: Higher cognitive scores were associated with a more favorable autonomic profile at rest, including higher standard deviation of normal-to-normal intervals, low frequency (LF), and very low frequency (VLF) and lower SNS and Stress Index values. During exercise, better cognition was linked to greater high frequency power and larger reductions in LF and VLF from rest to effort, indicating enhanced autonomic flexibility. Lower cognitive scores showed flatter LF/VLF trajectories and a sharper in-exercise decline in the PNS index. Higher body mass index was consistently related to reduced vagal modulation and higher sympathetic markers. Conclusion: Older adults with better cognitive performance show healthier resting autonomic profiles and greater adaptability of cardiac autonomic regulation during a brief functional test. Blunted HRV trajectories in individuals with lower cognition may signal early neurophysiological vulnerability, and 2-Min Step Test-derived HRV responses may provide a non-invasive marker of cognitive health in aging.