Assessing Stress Level Scores Against Wearables-Driven Physiological Measurements

Daily stressors elicit physiological and mental responses impacting health, cognition, and behaviour. Accurately assessing psychological stress responses in natural settings remains challenging despite extensive research, though wrist-worn devices have the potential to address this gap through remote data collection. The Garmin fitness tracker provides a stress score largely based on HRV which must be validated prior to use in research. This study aimed to (1) predict psychological self-reported stress from physiological measurements and Garmin calculated stress score, and (2) assess the stress score given by the Garmin Vivosmart 4 against HR and HRV from ECG recordings derived by the Polar H10 chest strap. A pilot study of 29 participants was conducted, followed by power calculations and preregistration of the main study which included 60 participants. Data were collected simultaneously from both Garmin and Polar device during a laboratory session of restful and mental-stress-inducing tasks. Garmin's stress score, mean HR, SD2/SD1, and HF power exhibited significant differences between stress and rest conditions. Moreover, Garmin's stress score correlated significantly with HR, RMSSD, and SD2/SD1. However, out of our physiological measurements, heart rate showed the strongest association with self-reported stress, while the Garmin stress score demonstrated only marginal predictive value for subjective stress experience. Our findings also suggest that physiological responses to mental stress were influenced by sex and tonic HRV. The study suggests that the GSS, although even better heart rate, are indicative of mental stress. Garmin, with its accessibility and noninvasive nature, measures both heart rate and consumer health score (stress), promising widespread utilisation in various research domains.