Association Between Heart Rate Variability and Brain Stiffness Across the Lifespan

High blood pressure (BP) and poor BP control are associated with a greater loss of cognitive function and brain structural integrity with aging. Since BP is partially regulated by the autonomic nervous system (ANS), ANS activity may have implications for maintaining brain health with aging. Interestingly, higher heart rate variability (HRV), a common noninvasive measure of ANS activity, has been associated with better overall cognitive function. However, few studies have assessed the association between HRV and brain structural integrity. To our knowledge, there are no current studies that have assessed whether HRV is associated with gray matter microstructural integrity. OBJECTIVE: To assess the association between HRV and brain stiffness using magnetic resonance elastography (MRE) in adults across the lifespan. We hypothesized that higher (“better”) HRV would be associated with higher (“better”) brain stiffness. METHODS: Young (22-29yr; n=10), middle-aged (51-63yr; n=23), and older adults (66-79yr; n=14) underwent supine resting electrocardiography for 5 minutes and MRE to assess whole-brain (WB) stiffness. LabChart’s built-in HRV module was used to measure HRV, including the standard deviation of RR intervals (SDRR), root mean square of successive differences (RMSSD), high frequency power (HF), low frequency power (LF), and LF:HF ratio. We assessed the association between age, HRV, and WB stiffness using Pearson (r) or Spearman’s (ρ) correlations. Regression analyses were performed with robust standard errors (HC3) to assess the relation of HRV with WB stiffness, controlling for age. HRV data that was not normally distributed was log transformed. RESULTS: Across the combined sample (22-79yr), as expected, age was negatively correlated with SDRR (ρ=-0.506, p< 0.001), RMSSD (ρ=-0.390, p=0.007), HF power (n.u.) (ρ=-0.374, p=0.010), and WB stiffness (ρ=-0.790, p< 0.001). Age was also positively correlated with LF:HF ratio (ρ=0.308, p=0.035) and tended to be positively correlated with LF power (n.u.) (ρ=0.263, p=0.074). WB stiffness was positively correlated with SDRR (r=0.338, p=0.020) and tended to be positively correlated with RMSSD (r=0.254, p=0.085) and HF power (n.u.) (r=0.271, p=0.066). However, when adjusting for age, SDRR, RMSSD, and HF power (n.u.) did not exhibit any significant associations with WB stiffness (all: p≥0.457), while age was a significant predictor of WB stiffness in all three models (p< 0.001). WB stiffness was not associated with LF power (n.u.) (r=-0.194, p=0.191) or LF:HF ratio (r=-0.204, p=0.169). CONCLUSION: HRV and WB stiffness were strongly associated with age; however, HRV was not associated with WB stiffness after adjusting for age. Longitudinal studies should be conducted to explore whether changes in autonomic function directly impact brain structural integrity and cognitive function. Supported by NIH grants, R01AG080052, P20GM113125, & P30GM145765, & AHA 24IAUST1199297. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.