A Comparative Study of Stress and Anxiety Estimation in Ecological Settings Using a Smart-shirt and a Smart-bracelet

In recent years, consumer wearable devices focused on health assessment have gained popularity. Of these devices, a large number target monitoring heart rate; a few among them include additional biometrics such as breathing rate, galvanic skin response, and skin temperature. Heart rate, and more specifically, heart rate variability (HRV) measures have proven useful in monitoring user psychological states, such as mental workload, stress and anxiety. Most studies, however, have been conducted in controlled laboratory environments with artificially-induced psychological responses. While these conditions assure high quality in the collected data, the amount of data are limited and the generalization of the findings to more ecologically-appropriate settings remains unknown. To this end, in this paper we compare the accuracy of two wearable devices, namely a smart-shirt measuring electrocardiograms and a smart-bracelet measuring photoplethysmograms. Several HRV features are extracted and tested as correlates of stress and anxiety. Data were collected from 196 participants during their normal work shifts for a period of 10 weeks. The complementarity of the two devices is also explored and the advantages of each method are discussed.