Standard deviation of pulse pressure measured using wearable devices improves the estimation of acute psychological stress

Recent technical innovations have increased the use of physiological information as objective indices for stress measurement. Early detection of acute stress can minimize long-term stress burdens by aiding in the prevention and treatment of stress-related physical and mental health problems. The standard deviation of pulse pressure (SDPP) has recently emerged as an objective index for measuring stress. However, the causal relationship between acute stress and SDPP has not been verified, and it is unclear whether SDPP can detect stress responses that conventional indices cannot. This study investigated whether SDPP, measured using a wearable device, can be used as a stress assessment index to detect acute psychological stress and improve the accuracy of stress estimation in healthy participants who were subjected to the trier social stress test (TSST). A total of 114 healthy volunteers were randomly divided into the stress- induced (Stressed) and non-stress (Control) groups. Heart rate (HR) and heart rate variability (HRV), which are indices of the autonomic nervous system, and salivary cortisol, an endocrine marker, were used as objective stress indices. Psychological evaluations (POMS2, STAI) were employed as subjective assessments. The relationships between these measurements and SDPP were evaluated. The results indicated that SDPP was significantly higher in the Stressed group, confirming that SDPP reflects induced stress. Furthermore, logistic regression analysis showed that adding SDPP to HR, HRV, and cortisol can improve the accuracy of estimating stress presence. Moreover, a multilevel analysis revealed that SDPP can enhance the estimation of psychological evaluation (POMS [total mood disturbance]) scores. The results suggest that SDPP can estimate the degree of stress experienced by an individual and monitor stress responses undetectable by conventional indices.