Key result
taVNS response in primary insomnia is linked to higher HRV and lower sensorimotor network fALFF.
Why the study?
Transcutaneous auricular vagus nerve stimulation is effective for primary insomnia, but efficacy varies across individuals for unclear reasons.
Does transcutaneous auricular vagus nerve stimulation (taVNS) alter spontaneous neuronal activity and heart rate variability in patients with primary insomnia?
Observational (n=40)
Does transcutaneous auricular vagus nerve stimulation (taVNS) alter spontaneous neuronal activity and heart rate variability in patients with primary insomnia?
Differential regulation of the sensorimotor network by the autonomic nervous system may explain inter-individual variations in taVNS efficacy for primary insomnia, with HRV and fALFF serving as potential predictive biomarkers.
HRV and sensorimotor fALFF may predict taVNS response in insomnia; hypothesis-generating for biomarker-guided therapy pending prospective trials.
Transcutaneous auricular vagus nerve stimulation (taVNS) has been reported to be effective in the treatment of primary insomnia (PI); however, its efficacy varies considerably across individuals for reasons that are unclear. In order to clarify the underlying mechanisms, this study investigated the effects of taVNS on spontaneous neuronal activity and autonomic nervous system function by functional magnetic resonance imaging (fMRI) and measurement of heart rate variability (HRV), respectively, in patients with PI. Forty patients with PI were divided into effective (group A) and ineffective (group B) groups based on their response to taVNS as determined by Pittsburgh Sleep Quality Index score reduction rate (group A ≥ 25% and group B < 25%). Spontaneous neuronal activity was measured by fractional amplitude of low-frequency fluctuations (fALFF) and HRV values and was compared between the two groups as well as before vs after taVNS. We then analyzed the correlations among efficacy of taVNS for 4 weeks, the fALFF and HRV values during continuous taVNS state. The results showed that the HRV parameter values (i.e., root mean square of successive differences, percentage of adjacent NN intervals differing by >50 ms, and high frequency) of group A were higher than those of group B during continuous taVNS state. In the fMRI scan, the fALFF values of the right cerebellum, right medial superior frontal gyrus, and bilateral supplementary motor area—which belong to the sensorimotor network (SMN)—were lower in group A than in group B during continuous taVNS state. The correlation analysis revealed that the efficacy of continuous taVNS and HRV and fALFF values were interrelated. These findings demonstrate that differential regulation of the SMN by the autonomic nervous system may be responsible for inter-individual variations in the efficacy of taVNS and suggest that HRV and fALFF are potential biomarkers for predicting PI patients’ response to taVNS treatment.
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Wu et al. (2021) conducted an observational in Primary insomnia (n=40). Transcutaneous auricular vagus nerve stimulation (taVNS) vs. Ineffective response (<25% PSQI reduction) was evaluated on Spontaneous neuronal activity (fALFF) and heart rate variability (HRV). In patients with primary insomnia, response to taVNS (≥25% PSQI reduction) was associated with higher heart rate variability and lower sensorimotor network fALFF values during continuous stimulation.
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