Fig. 1.

tcVNS without acute stress: Outcomes for stimulation without acute stress, merged from all days. Bars represent the unadjusted mean changes from baseline, error bars: 95% confidence interval (CI), values calculated from raw data, * indicates p < 0.05. β coefficients, adjusted CI, effect sizes (d), and p-values were reported in β (±CI, d, p) format. Active tcVNS group experienced the following relative to sham after adjustments: (A) The ratio of short-term variability to long-term variability (SD1/SD2) increased following stimulation by 14.1% (±11.6%, d = 0.43, p = 0.019). (B) Heart rate (HR) decreased following stimulation by 2.7% (±2.0%, d = 0.21, p = 0.009). (C) Photoplethysmogram (PPG) amplitude increased during stimulation by 43.4% (±43.4%, d = 0.53, p = 0.049) and following stimulation by 73.1% (±63.2%, d = 0.67, p = 0.025). (D) Pulse arrival time (PAT) increased during stimulation by 2.5% (±2.2%, d = 0.26, p = 0.026).