I’m slightly conflicted about wearing my Apple Watch while sleeping. I don’t suffer from sleep apnea or have any particular trouble sleeping, and being informed about occasional bouts of early morning insomnia doesn’t tell me anything I didn’t already know. Learning that I spent an average of 7 hours and 32 minutes asleep every night over the last month is slightly interesting but not particularly actionable.
(Obviously, your mileage may vary. Many people have sleep issues and may benefit from connecting poor sleep nights with particular foods, alcohol, or activities.)
However, some of the data that the Apple Watch collects during sleep is more valuable. I’ve paid more attention to my heart rate ever since a fainting incident in 2022 while climbing a via ferrata route at Whistler in British Columbia. I was at 7000 feet, cold, wet, and exercising, which should have increased my heart rate and blood pressure. Instead, I experienced a “paradoxical vasovagal response,” where my heart rate and blood pressure suddenly dropped, and I passed out on a ledge—happily, while clipped into the steel cable. It was a lot of fuss for what turned out to be a fluke incident.
Until then, I hadn’t realized my heart rate could drop problematically low. Now that I regularly wear the Apple Watch at night, the Health app sometimes warns me that my heart rate has dropped below 40 bpm for more than 10 minutes. I’m unperturbed by occasional warnings, but if they were to become more frequent, another discussion with the cardiologist might be warranted.
I was more intrigued when Apple announced that watchOS 11 would feature a new Vitals app for tracking heart rate, respiratory rate, wrist temperature, blood oxygen, and sleep duration. Only respiratory rate and wrist temperature were new, but Apple suggested that combining all five could provide a greater understanding of daily health status.
The question is, what would it tell me? If I were training hard, some abnormal vitals might suggest adjusting a tough workout, but that’s not a concern at the moment, and relatively few people exercise intentionally enough to care. I suspect most, like me, are more curious about common diseases like the flu, COVID-19, and colds. Would the Vitals app be able to detect that I was coming down with something?
Apple doesn’t want to admit this, saying, “Vitals is not designed to detect illness or a medical condition.” Those feel like weasel words from lawyers designed to absolve Apple of liability and avoid making claims to which the FDA might take exception. But who wouldn’t wonder if measurements beyond one’s baseline suggest an oncoming illness or medical condition?
Whether or not Vitals is designed to detect illness, can it do so? The answer—in my only opportunity to test the feature so far—is yes, although the news came as no surprise since I had already decided I was sick before receiving the first abnormal report. Nevertheless, learning that my vitals were out of whack might have been helpful if the timing had been slightly different.
On Sunday of last week, I didn’t get as much sleep as usual due to having to wake up early to direct a track meet. I was on my feet from 7:30 AM to 2:30 PM, so I wasn’t surprised to be tired afterward. But when I didn’t feel any better by dinnertime, I suspected I was getting sick. Indeed, when I woke up late on Monday morning, the Vitals app reported four outliers: increased heart rate, respiratory rate, wrist temperature, and sleep duration. (Blood oxygen remained stable, which seems positive.) That evening, I tested positive for COVID-19. The symptoms weren’t terrible, but Tuesday and Wednesday also showed elevated respiratory rate and wrist temperature. Thursday’s numbers were all back in range, and while I wasn’t well, the symptoms had abated even further.
The three days I was most sick are glaringly obvious in the weekly Vitals chart in Health (above left). They stand out even more in the six-month chart (above right), which shows that the only other outliers I’ve had since September were a couple of nights when I couldn’t sleep and read for a few hours at night. In other words, the only real outliers have been when I was ill.
It’s presumptuous to draw significant conclusions from a single data point, but I plan to keep wearing the Apple Watch at night to see if outlying vitals might be helpful again. How about you? If you sleep with the Apple Watch on your wrist, has the Vitals app told you anything you didn’t already know?
