This is fascinating: smart watches can predict if you have COVID a week before you're symptomatic!

It has to be a smart watch of fitness tracer that has a pulse monitor that also tracks heart rate variability (HRV), such as the Apple Watch 4-6. Some Fitbits and Garmins do this.

Here's the deal. You like to think your heart beats very regularly, the old phrase "his heart beat like a Swiss watch." It doesn't. The pause between each heart beat is slightly variable, hense HRV. HRV is measured in milliseconds and it varies throughout your day. At night it falls into a circadian pattern.

Now for the weird stuff. If you catch COVID, your HRV becomes LESS VARIABLE. Up to something like eight days before you become symptomatic, this is detectable!

They ran a small research program at Mount Sinai Hospital and several other hospitals, the Mount Sinai's program enrolled some 260 people who worked there who had an iPhone 6 or better, and an Apple Watch 4 or better. They loaded a program made in-house called Warrior, the people wore their watches for at least 8 hours a day, and tried to take daily surveys for how they felt. If they started feeling sick, they got a nasal swab PCR test, and if that was positive, they pulled the heart rate data for them and analyzed it. And started finding the data that I mentioned in the previous paragraph!

Now, the Apple Watch, and I assume the others, measure your pulse through shining an LED through your skin and it bounces through and is picked up by a photo diode that measures the result. That's how the pulse oxymeters that they slip on your finger in the doctor's office work. My watch will alert me if my pulse gets too high and stays there for an extended period. As far as I know, Apple isn't doing anything to notify you if your HRV becomes less variable, but the potential is there. They could be waiting for the papers to be peer reviewed or for the FDA to give approval or something. It's just like the fact that my Apple Watch 5 can do a three-lead ECG, it can't detect if I'm having a heart attack.

I don't know about how smart watch tracking works on non-Apple devices since I don't know them, but I can look at my HRV and see how it changes over a week or month. If you look at a year's worth of data, the averages smooth out too far to see any appreciable deviation.

Still, pretty nifty and another way to detect COVID!

There's a link in the CBS article to the Mount Sinai Warrior Watch study. It's not difficult to follow if you skip the more dense paragraphs.

https://www.cbsnews.com/news/covid-symptoms-smart-watch/

While speaking of Apple Watches, the next one may have real time glucose monitoring!

Apple never confirms rumors prior to the product launch event, but it is rumored that the Watch 7, which will be revealed (I think) in September or October and usually released a month later, will have the ability to record real-time glucose information! This will be a major thing for diabetics and pre-diabetics! And if you're not one of those two, you can still record and log the information and see if you have a trend developing or not.

Apple has been introducing medical monitoring sensors progressively with their watches. The article mentions that Tim Cook, CEO of Apple, says 'we have all these sensors for our cars, and our bodies are far more important.' I completely agree! I personally have little need for a pulse monitor because I'm not an exercise junkie, then I read that article about smart watches detecting COVID early. Now I love the idea!

The Apple Watch 4 had a pulse monitor, the 5 introduced a three-lead ECG, the 6 an SpO2 sensor. The Apple Watch 7 will not be the first smart watch to feature glucose monitoring, apparently Samsung did that with their Watch 4. Still, lots of people prefer the Apple environment, so this opens up that tech for them.

The Apple Watches only work with Apple iPhones and you must have one to configure it and log medical data (you might be able to use an iPad to do that), I don't know if the Samsung watches will work with iPhones or if they require Android phones.

I was reading the comments on the Slashdot thread about this, and some people think it is reading glucose in the interstitial tissue, not directly in blood vessels. This makes sense, as blood vessel positioning is not only variable from person to person, but you might change where you wear your watch during the day, or it might shift a little. Thus an interstitial measurement might make more sense for a little more consistency in measurement. This makes the question of how fast reacting is that measurement compared to blood levels from an event like taking Glucophage is downing a soda or something. I'm not diabetic, I've never studied the disease, I really don't know. Ask me questions about hypogammaglobulinemia, and I can speak with some limited authority.

Still, from what I've read about the accuracy of some of the real-time monitors, it can't be any worse! And if it greatly reduces the number of needle sticks, it will definitely be a blessing.

https://www.macrumors.com/2021/01/25/apple-watch-series-7-blood-glucose-monitoring/