The study examined 104 older adults aged 60-85 from southern Chile and found that those with better cognitive performance had a healthier autonomic nervous system at rest, including higher heart rate variability and lower stress levels. During the two-minute step test, persons with better cognitive performance showed greater autonomic flexibility and a better ability to adapt cardiac regulation to physical load. Conversely, older adults with lower cognitive performance had less variable cardiac responses to exercise and a greater decline in parasympathetic activity during exercise. Higher body mass index was consistently associated with decreased nervous system regulation and higher markers of stress. The researchers concluded that cardiac variability responses from a functional test may serve as a noninvasive marker of cognitive health in aging and that blunted cardiac variability trajectories may signal early vulnerability of neurophysiological processes.