Dear Editor,
The article by Chou et al. on autonomic modulation and risk of dementia in a middle-aged cohort [1] is a valuable contribution to the sparse existing literature on the longitudinal association between heart rate variability (HRV) and cognitive decline, and provides support for the biomarker potential of HRV. In terms of time- and frequency-domain HRV, the Authors found that the likelihood of all-cause dementia was increased by low standard deviation of normal-to-normal RR intervals, reflecting lower parasympathetic modulation, and high low-to high-frequency power ratio, indicating greater sympathetic dominance.
Among the possible mechanisms linking autonomic dysfunction and dementia, we believe an important unmentioned explanation relates to the Central Autonomic Network (CAN), a complex system of brain regions that is responsible for both cognition and autonomic regulation, and is therefore acknowledged as the neural correlate of the brain-heart axis [2,3].
In particular, there is increasing evidence that different components of the CAN are involved in different cognitive processes and in sympathetic versus parasympathetic autonomic control [2,4]. Accordingly, in a recent longitudinal study, we reported that, in older subjects with mild cognitive impairment, a greater HRV response to a sympathetic challenge predicted a greater decline in episodic memory whereas a greater HRV response to a parasympathetic challenge predicted a lesser decline in executive functioning [4].
While our general observation of greater cognitive decline with higher sympathetic and lower parasympathetic activation is in line with the results from Chou et al., our finding of a differential association between the two autonomic branches and specific cognitive domains still awaits confirmation. We suggest that future large prospective studies should also address continuous outcomes (i.e. cognitive test changes) in order to foster a more granular understanding of the relationship between autonomic modulation and cognition, even in the light of the CAN's site-specific functions.
Footnotes
Peer review under responsibility of Chang Gung University.
References
- 1.Chou YT, Sun ZJ, Shao SC, Yang YC, Lu FH, Chang CJ, et al. Autonomic modulation and the risk of dementia in a middle-aged cohort: a 17-year follow-up study. Biomed J. 2022;46(6):100576. doi: 10.1016/j.bj.2022.12.004. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Thayer JF, Hansen AL, Saus-Rose E, Johnsen BH. Heart rate variability, prefrontal neural function, and cognitive performance: the neurovisceral integration perspective on self-regulation, adaptation, and health. Ann Behav Med. 2009;37(2):141–153. doi: 10.1007/s12160-009-9101-z. [DOI] [PubMed] [Google Scholar]
- 3.Silvani A, Calandra-Buonaura G, Dampney RA, Cortelli P. Brain-heart interactions: physiology and clinical implications. Philos Trans A Math Phys Eng Sci. 2016;374(2067) doi: 10.1098/rsta.2015.0181. [DOI] [PubMed] [Google Scholar]
- 4.Nicolini P, Lucchi T, Abbate C, Inglese S, Tomasini E, Mari D, et al. Autonomic function predicts cognitive decline in mild cognitive impairment: evidence from power spectral analysis of heart rate variability in a longitudinal study. Front Aging Neurosci. 2022;14 doi: 10.3389/fnagi.2022.886023. [DOI] [PMC free article] [PubMed] [Google Scholar]