The relationship between heart rate variability and baseline state anxiety during stress and recovery

Baseline state anxiety, which reflects an individual’s initial anxiety level before stressors, offers an important perspective for understanding how pre-existing anxiety influences responses to subsequent stressors. This study investigated physiological changes in 59 participants grouped by low (n = 32, LbSA group) and high (n = 27, HbSA group) baseline state anxiety levels, measured using the Short State Anxiety Inventory. Participants underwent three phases: baseline (T1), the modified Trier Social Stress Test (TSST) task (T2), and recovery (T3). ECG signals were recorded and six heart rate variability (HRV) features were analyzed across time, frequency, and non-linear domains using a mixed linear model. In T2, the LbSA group showed significantly increased SDNN (t= 2.662, p= 0.027) and decreased RR_Mean (t= -6.819, p< 0.001) and SampEn (t= -2.985, p= 0.010). In contrast, the HbSA group only showed a decreased RR_Mean (t= -5.641, p< 0.001). In T3, the HRV changes in the LbSA group rebounded, whereas the HbSA group did not, resulting in significantly increased SDNN (t= 3.187, p= 0.006), RMSSD (t= 3.719, p= 0.001) and LnLF (t= 3.800, p= 0.001). Additionally, between-group differences reached significance for SampEn in T2 (t= 1.301, p= 0.044) and for SDNN (t= 2.215, p= 0.036) and RMSSD (t= 2.209, p= 0.046) in T3. Compared to the individuals with low baseline state anxiety, which shows rapid changes under stress and quick recovery afterward, the individuals with high baseline state anxiety exhibit blunted and prolonged responses. The findings highlight the potential influence of baseline state anxiety on autonomic regulatory capacity, suggesting the importance of modulating state anxiety.