Apple Watch heart rate display
A study published by Frontiers in Digital Health suggests the Apple Watch series may be ready to get built-in stress tracking, a metric not currently measured by this smartwatch family.
Most Apple Watch rivals offer some form of stress tracking, but Apple has held out. The study undertaken by researchers in the University of Waterloo suggests the watch does have the hardware to make it work, though.
The small-scale study used the Apple Watch’s ECG sensor to record HRV measurements and cross-reference them with questionnaire data from the participants.
They were asked over a two-week period to record readings six times a day at three-hour intervals, and to record how stressed they felt at each reading.
The study found the Apple Watch was roughly “in line with the start-of-the-art for stress prediction,” although is actually better at determining when you are not stressed rather than when you are.
Its conclusion suggests more work could be done using the various ways to calculating heart rate variability, and “deep learning”, to yield better results. This is the least Apple would do when designing a set of stress-sensing algorithms, of course.
The study itself was quite limited. Its initial participant count of 40 was whittled down to 33 used for the final data set and, as the authors note, “white females” were significantly over-represented.
Why not stress in the Apple Watch?
There is another reason for Apple to largely ignore these findings — other than that it is probably well aware of its watch’s own abilities to measure heart rate variability.
This method of analyzing stress relies on the wearer placing a finger on the watch’s crown for 30 seconds straight. And the study notes the single 30-second stress sessions an actual person is likely to do may not give the watch enough data for a solid prediction.
Even this may be too much to ask of Apple Watch owners, though. In almost every case, watches that ask for this sort of active participation eventually get overtaken by a “passive” alternative that can run in the background.
For example, the Fitbit Sense 2’s main upgrade over the Fitbit Sense is an EDA stress sensor that can flag potential stress events throughout the day, not just when the wearer starts a stress-tracking session.
Apple now offers passively-collected Irregular Heart Rhythm data as a companion to ECG heart health readings, where the person has to sit still and place a finger on the crown.
Given Apple already appears to have learned Watch owners prefer passive forms of health tracking to active ones, it seems unlikely the company will add an active-participation form of stress tracking without a passive adjunct.
However, stress is one avenue Apple may explore at some point, particularly given the watch already measures HRV at points — a key stress metric.
The ECG tech used in the original study is available in the Apple Watch Series 8 and Watch Ultra, but not the Apple Watch SE.
