Measuring stress using wearable devices

Over 200 million individuals experience anxiety or chronic pain. Assessing the intensity of anxiety and pain involves patient-assessed subjective ratings. However, these are limited by differing personal perceptions and variability. An unbiased, objective stress metric could help overcome these challenges, enabling better management. Many wearable devices provide a stress measurement derived from heart-rate variability, which has been shown to decrease with stress. This study used a Garmin’s smartwatch stress metric to measure the stress of 12 female and 15 male participants during a 20 min long Colour word test (CWT) inducing a stress/anxiety response, and a 90-second Cold pressor test (CPT) inducing a pain response. To quantify the strength of a response, two metrics were defined. These were, Baseline factor, which is participant stress increase relative to basal stress, and Headroom factor, which measures how close the stress response got to 100%. Both are on a 0.00-1.00 scale.

The mean Baseline and Headroom factors for the CWT were 0.46, and 0.38. The mean Baseline and Headroom factors for the CPT were 0.06, and 0.12. CPT results were less consistent than CWT results, possibly as a result of the CPT’s shorter duration or subject-specific pain responses. There were no clear differences in Baseline or Headroom factor results by sex.

These results suggest smartwatches could offer an objective metric to measure stress or pain in real-time, with applications in the assessment and management of anxiety and chronic pain, as well as a tool in clinical trials to evaluate the effectiveness of stress-reducing interventions.