watchOS 11’s Vitals App May Detect Illness

Originally published at: https://tidbits.com/2025/01/21/watchos-11s-vitals-app-may-detect-illness/

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 fallen 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 thus 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.

Vitals app on Apple Watch and Health app description

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 hadn’t fully recovered, the symptoms had abated even further.

Vitals charts in Health

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. 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 indicate illness 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?

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Not conflicted…but I agree. We bought series 9s last year to replace the series 5s…and we wear the 5s to sleep but the sleep analysis isn’t any real use to us. I wear the 5 on bike rides…but only because it’s got a silicone band that doesn’t soak up sweat like the Velcro ones do and because I’ve got one of those glass covers on the 9 that gets sweat underneath if I wear it on warm days and then I need to take it off and dry everything.

When the 5 battery won’t last the night anymore I will go back to sleeping without.

I’ve been wearing my Ultra at night for almost a year. Back in February I had reason to set an alarm and I decided to do it on both my phone and my watch. The watch offered to turn on sleep tracking, and I’ve been doing it ever since.

I don’t find the results useful. I do get a low heart rate warning almost every night. (I looked into lowering the minimum to below 40, but it’s not possible.) The only interesting thing is what time it happens. Usually it’s within a hour of me getting up in the morning, on rare occasions it happens within an hour of falling asleep. Since Vitals arrived there’s only been one day where they’ve been abnormal (HR, breathing and temperature all above normal), a day back in November where I ran an actual fever for about 6 hours. I tested negative for COVID that time, but it was similar to when I had COVID years ago, which was also an inconvenient 6 or so hours. Other than that, my vitals are always within range, so they’re also not very useful. I’ll continue wearing my Ultra at night, but if I had to stop for some reason, it’d be no great loss.

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Just interested to know which Watch models and OS support this app.

It’s any watch that supports watchOS 11. It’s a built-in feature of the OS. You can also see the data on the iPhone in the Fitness app and the Health app, which is where I always look.

If you are in the US and bought your Series 9 or 10 or Ultra 2 watch after January last year, or you have an SE 2 model, it likely shows only three components rather than four, as the oxygen sensor is either disabled or isn’t on those watches. That said, as someone who has a watch with the oxygen sensor, I don’t its readings very seriously. They tend to look wildly inaccurate to me (e.g., my readings are sometimes in the low 80s. As someone who averages about 75 minutes per day of aerobic exercise and regularly gets those under 40 heart rate readings while sleeping, I find that pretty unreliable.) To be fair, it’s the background readings while sleeping that look bad to me. If I take a reading using the blood oxygen app the way they recommend - with your wrist resting and the watch pointing up while it’s reading - the readings look fine.

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I wear my watch most nights and see similar low heart rate warnings, typically about once a week. It was actually useful when I needed a minor surgery last year as I could warn the
anaesthetist my heart rate might get very low (I’ve seen as low as 37bpm).

As per others, it’s typically in the last hour before I wake. One thing I have definitely noticed is the difference in heart rate after I’ve been unwell. I had a virus last year and I noticed my heart rate was considerably higher than normal when doing my regular rock climbs. When I was fully well it returned to normal.

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Vitals has actually picked up a couple things for me, though not illness (thus far): my wife and I both did the shingles and pneumonia vaccinations on the same day late last year, and Vitals picked up the slight fever, respiratory rate change, and sleep disruption the night after we got the shots. Also, I had a tooth ache in late October that turned into a root canal, and the night before I was able to get into my dentist and get antibiotics prescribed, Vitals picked up heart rate, respiratory rate, temperature, and sleep abnormalities.

Also, I’ve been sleep tracking for a few years with my watch, mostly out of curiosity. The addition of Sleep Apnea detection last year has been helpful for me, as I was diagnosed with a relatively mild case back in 2016, and have been wearing a mouth guard that helps open my airway ever since. I also recently added mouth taping, as even with the mouth guard, I was sometimes breathing loudly through my mouth, which affected my wife’s sleep (she struggles with mild, occasional insomnia). My hemoglobin is still running somewhat high (a sign of apnea that can lead to heart issues or stroke if it gets too high), but I haven’t had any apnea detections from my watch, so it appears that my apnea is well-controlled without having to look into a CPAP.

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For everyone who wears their watch to bed - when do you recharge it? I don’t like charging during the day because then it misses out on activity.

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I charge it when I use the shower in the morning and when I do some web catch-up before I go to bed. However, I could probably survive doing only one of those, as the watch is usually down about 20-30 percent from its max charge of 80 percent. Note that it fast charges to 80 percent, so these sessions take only 15-20 minutes.

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Typically I charge after dinner when I’m taking it easy: watching TV, surfing the web or talking to the family. It’s usually at 100% before bed. I exercise early so it lasts through that and I’ll put it on charge again. If I sit down to do some work I can charge it then as well.

Little top-ups through the day get me through most things.

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I’m the same as Alan - I charge while I shower after my workout and then breakfast in the morning, and I charge while I am washing up for bed. I read in bed for at least ten minutes almost every night, so when I put the book down I take the watch off charge and put it on and unlock it. Every once in a while it needs a charge beyond that, so in those cases I put it on the charger while I eat supper. I also have a charger in the car, and I’ve charged while driving somewhere. In fact, I do this any time I have to drive to run a half marathon just so I know that I’m starting the race with a relatively full charge.

I have an Ultra, so battery is much better than the other watches. Honestly I think this is what battery life should be at a minimum for all Apple Watches.

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I recharge mine whenever I’m doing an activity. Before I get on the bike (or go out to ski or hike), I pop it onto the charger, and it’s ready when I’m done (typically 80 minutes, sometimes longer). I never use it for activities, so that’s the perfect time to charge it. Today is a rest day, so I’ll put it on the charger when I shower, and wear my Garmin Epix until my Ultra is ready.

Ditto on the low heart rate warning while sleeping (always 39), but I’ve never gotten a wrist temperature reading on my Apple Watch 10, currently running OS 11.2 (and upgrading to 11.3 today).

I charge when the watch tells me to charge :wink:. Also often the watch tells me to charge an hour of so before I go to sleep.

I just learned about this Vital thing because of your article! Most readings (heart, sleep, respiratory) I already checked in the “main” app, but now I added the Vitals part, because of the temperature reading it is supposed to give me, which can be interesting.

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It isn’t a case of the FDA might take action but rather they will. Apple has run all their medical features past the FDA and I assume the equivalent in other countries and will be making sure that it is not classed as a diagnostic product.

Thanks Adam! Good use case. I’ve been using my older Watch to monitor sleep for general data and help making adjustments to my patterns. I’m going to try switching to my 9 series Watch for overnight monitoring and collect Vitals data. The key will probably if my older Watch can hold enough charge for my morning exercise while the series 9 is charging for the rest of the day.

Hopefully your bout with Covid is “one and done” free of long term issues.

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