Cognitive changes and emotional heart rate variability dynamics in subjective cognitive decline: An exploratory longitudinal neuropsychophysiological study

Subjective cognitive decline (SCD) is increasingly recognised as a potential preclinical stage of Alzheimer's disease, yet the physiological mechanisms underlying its progression remain poorly understood. This longitudinal study examined whether heart rate variability (HRV), a non-invasive marker of autonomic nervous system regulation, could serve as an early psychophysiological indicator of cognitive vulnerability in older adults with SCD. Twenty-one participants meeting established SCD criteria completed two identical experimental sessions approximately 12 months apart. Each session included comprehensive neuropsychological testing and continuous HRV recording during exposure to emotionally evocative images from the International Affective Picture System, presented in a temporally extended and affectively rich paradigm known as an "affective storm". At the group level, no significant changes in cognitive performance or HRV indices were observed over time. However, analyses of individual change scores revealed that longitudinal variations in HRV, particularly in indices reflecting parasympathetic tone and overall autonomic flexibility, were selectively and consistently associated with performance in global cognition, verbal fluency, and visuospatial working memory. These findings suggest that dynamic autonomic responses to emotional stimulation may reflect subtle physiological correlates of cognitive functioning, even in the absence of overt cognitive decline. The observed associations are consistent with neurovisceral integration models, and support the potential utility of HRV as a sensitive, non-invasive marker of early cognitive trajectories in ageing. In conclusion, HRV may offer unique insights into the complex interaction between emotional reactivity and cognitive resilience in older adults with SCD, opening promising avenues for early screening and intervention.