Study Finds An Apple Watch Can Predict Your Stress Level With Surprising Accuracy

A new study has determined that the Apple Watch can be fairly adept at predicting stress levels of its users. The study was performed by a team of researchers from the University of Waterloo, Canada.

The Apple Watch is a highly-popular smartwatch that has many useful features and functions. From being able to check text messages and take a phone call, to tracking your heart rate and sleep patterns, the Apple Watch can indeed make life a bit easier. However, a new study also details how the smartwatch can also predict stress levels with a high degree of accuracy, even though it's not currently a feature Apple offers in its smartwatch line-up.

Participants of the study were given an iPhone 7 with iOS 15.0 and an Apple Watch Series 6, which had an Apple Watch ECG app installed. The study took place over a two-week span. The participants were then instructed to collect data 6 times during the day at approximately three-hour intervals. Before taking an ECG reading, the participants were also asked to complete a stress questionnaire on the iPhone.

Participants were given a total of 8 questions to answer in order to determine their current stress level. Question 8 was a single-item measure, that was previously used successfully in stress measurement questionnaires, with a moderate correlation to robust stress levels, according to the study's authors.

An Apple Watch has the capability to monitor a user's heart rate variability (HRV). Apple, however, does not use the data for any type of native stress level monitoring as other smartwatches do. A user's HRV can be determined by utilizing the smartwatch's electrocardiograph (ECG) sensor. The team then took that measurement and applied machine learning techniques to develop a stress prediction tool.

Researchers found "In general, the 'stress' models had a high level of precision but lower recall. The 'no stress' models performed generally well with a recall typically above 60%. Considering the ultra-short duration of the ECG measurements performed here compared to the standard, as well as the nature of real-life measurements, the results presented were quite promising."

The study also stated that other features of the Apple Watch could enhance the accuracy of a stress test, such as sleep and physical activity. Perhaps Apple will read the study and add a stress-tracking app in a future WatchOS release.