Effects of transcutaneous vagus nerve stimulation on motor function in older adults: a randomized crossover study.

BACKGROUND

Aging is associated with declines in gait performance and autonomic regulation, increasing the risk of functional limitations. Auricular transcutaneous Vagus Nerve Stimulation (tVNS) is a promising non-pharmacological intervention, but its acute effects on gait in older adults remain unclear. This study investigates whether acute tVNS can improve gait performance and autonomic function in healthy community-dwelling older women.

METHODS

A prospective, randomized, blinded, crossover trial was conducted with 17 healthy older women (≥60-years). Participants received active tVNS (left ear, 25 Hz, 500 μs, 30-min) and sham stimulation (right earlobe), separated by a 24-hour washout period. The primary outcome was the distance covered on the 6-Minute Walk Test (6MWT). Heart Rate Variability (HRV) was assessed as a key secondary outcome.

FINDINGS: Active tVNS significantly increased the resting Inter-Beat Interval (IBI, p = 0.008) and reduced heart rate (p = 0.03), indicating enhanced parasympathetic modulation. Sympathetic activity (LF and LF/HF ratio) decreased following active stimulation. Although absolute 6MWT distance did not significantly change (p = 0.07), the predicted walking distance improved significantly with active tVNS compared to sham (p < 0.01; Cohen's d = 0.65; mean difference -7.2%). Other clinical parameters remained unchanged.

INTERPRETATION: This first randomized crossover trial investigating the acute effects of transcutaneous vagus nerve stimulation in healthy older women demonstrated enhanced parasympathetic modulation and improved performance relative to predicted walking capacity. However, the primary outcome, absolute 6-minute walk distance, did not reach statistical significance. These findings should therefore be considered preliminary and hypothesis-generating, supporting the need for larger trials to determine the long-term clinical relevance of tVNS in older populations.