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The science behind on-the-wrist blood pressure tracking

empirical.health

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Re: The science behind on-the-wrist blood pressure tracking

#51

Post by corry »

LorenPechtel wrote: post #49
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

I found the exact reverse with the jog. One day I went into the mountains with a cuff on my wrist and took a bunch of measurements. I wasn't jogging but I had something like 25 pounds on my back and was definitely pushing myself. There was a huge effect from perceived temperature--while I didn't do the cold plunge I got some quite high readings when I was on the chilly side. Yet I could get low-normal readings with m…

Thanks for sharing. For me, I can see that DURING exercise, my blood pressure is quite raised but then drops down lower than usual in the hours that follow. However, I think that's more a function of resting HR - which remains elevated.

My particular BP scenario is good diastolic, high systolic but low rest heart rate (low 50s). My pet theory is that my heart does fewer but stronger pumps, which increases the BP. After exercising, when heart rate remains elevated, the BP is lower since the heart is doing more frequent but less powerful beats.

Just a pet theory, I haven't even discussed it with a medical professional.

Re: The science behind on-the-wrist blood pressure tracking

#52

Post by mikesabbagh »

I got a Xiaomi GT3 watch for less than 40$ including shipping. it has blood pressure measuring. How accurate? I dont know. I have a normal BP, and it always shows me normal values. Whe I try it on my son or wife's wrist, it always measures a lower BP.

Anyways, I stopped looking at it, and I only use it for the looks and to show me notifications.

Re: The science behind on-the-wrist blood pressure tracking

#53

Post by Etheryte »

mikesabbagh wrote: post #52

I got a Xiaomi GT3 watch for less than 40$ including shipping. it has blood pressure measuring. How accurate? I dont know. I have a normal BP, and it always shows me normal values. Whe I try it on my son or wife's wrist, it always measures a lower BP. Anyways, I stopped looking at it, and I only use it for the looks and to show me notifications.

Have you considered comparing it to a regular blood pressure monitor in parallel? My guess is that since it isn't certified as a medical device, it's essentially just a random number generator. No smart watch from a big name brand offers this feature yet, so I doubt a $40 device has figured it out.

Re: The science behind on-the-wrist blood pressure tracking

#54

Post by corry »

Etheryte wrote: post #6
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

This is super exciting, thanks for posting! I developed high blood pressure after Covid and have done a few 24h studies to better understand it. The traditional machines are super bulky, essentially like carrying a regular BP monitor around with a pouch that's strapped to you, maybe just a bit smaller. All in all it's far from convenient and can kick in at inopportune times. Having around the clock insights would hop…

Hey I have firsthand experience with it as indicated in the post. Probably a few months worth of wear at this point.

BP remains a great mystery to me, even with the device. My cardio fitness is pretty good despite carrying a few extra pounds (I'm in the low 50s for resting heart rate), and while overnight I dip down in the 120's, I can see it shoot up based on various things like cold plunge, caffeine, exercise (during), etc. I can also see it drop temporarily (hot tub, meditation, the hours FOLLOWING intense exercise, etc).

I had many pet theories through the years - that I had white coat syndrome, that I disliked the feeling of the cuff, etc etc. But the device showed me that, no, something really is going on independent of these pseudo-causes.

BTW water retention seems to play a big role. When I did keto, which causes a big drop in water retention, my BP also went down. Strange. Supplements have an impact too.

All this to say - get the device and see for yourself, but you might find yourself in the same place I am - which is that you have much better understanding of what's going on in terms of symptoms but are still on the search for "the underlying cause" if there even is such a thing.

Re: The science behind on-the-wrist blood pressure tracking

#55

Post by ljosifov »

rootusrootus wrote: post #16
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

IIRC there's also a Samsung Galaxy Watch that does blood pressure monitoring, with similar requirements. Have to work a bit to get the app installed in the US, but then it takes periodic measurements, is fairly accurate, and requires calibration once a month. I was really hoping Apple was going to bring BP to the watch this year, but my guess is the regular external calibration requirement is too much for their plug-…

+1. I also use Samsung Galaxy Watch (Active2) and find it to work well for me. I'm surprised more people don't know about it. I know couple of people that suffer from high BP. They showed little interest when I told them about the watch.

Regular external calibration helped me build confidence. I was suspicions if the watch worked, and how well it worked. Calibration is every month - it expires. I take 3 measurements in parallel watch-cuff, and tell the watch App what the cuff measured. I didn't mind it initially. I now find it annoying tbh. I see why Apple would like to get rid of it. Post calibration, I measure 3 times in parallel both watch and cuff to check if they match. If the difference is within 5% - then fine. In 3 years it's happened twice where they differed more and I had to recalibrate. From recollection - both times with a reason, a TV was turned on in living room.

I have the impression that BP measurements differ though the day (lower in the morning, higher in the evening), depending on activity or at rest of course, I think there maybe some seasonality too (winter v.s. summer). Measuring BP when going to the doctor once a year strikes me as a wholly inadequate. If the BP is absurdly high out of normal range - then yeah, we learn something is wrong with the patient. But in any other case - don't see what can be deduced from 1 random measurement.

To check if the calibration is important, I had my wife use the watch, that is calibrated on me. She got absurd readings. So yes - the calibration is important and is tied to the person that did the calibration. (edited to add this)

Re: The science behind on-the-wrist blood pressure tracking

#56

Post by corry »

sph wrote: post #19
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

> And goes without saying, your blood pressure SHOULD go up and down based on your activity and time of day. You just aren't used to seeing it other than at true rest. Yeah, people panic reading a single 150 systolic, yet routinely it can reach 220+ during heavy exercise. It's perfectly fine. The health metric is the BP at rest, i.e. how low it goes when you're completely idle. I find it takes up to 20 minutes to rea…

100% hard agree. I'm now paying most attention to my overnight rate, like in the middle of the night - but even that takes a few hours to get down to the minimum value. Fascinating to see the big spike prior to waking up that signals your body is preparing for rising.

Did I eat late before bed? Higher BP overnight. Drink any alcohol at all after, say, 12pm? Higher BP overnight. So it's still useful and interesting to see the overnight values change and shift around.

However, the contrarian in my mind says that it's not smart to ONLY pay attention to your deep rest state BP, since that only applies to a fraction of the day. And if you're running around at high values for the rest of the day, you're still potentially doing damage to your kidneys, retinas, etc - the sensitive blood vessel stuff.

So it's a useful device, it's useful to have the data, but it's also still a bit of black box.

The fact that 80% of all high blood pressure is of unknown physiological cause is a real head scratcher considering that cardiac misadventures are the leading cause of death in the Western world.

Re: The science behind on-the-wrist blood pressure tracking

#57

Post by corry »

brandonb wrote: post #7
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

I'll bet blood pressure readings throughout the day will be analogous to the data we get from CGMs (continuous glucose monitors). You get lots of spikes during the day. Given enough data pairing continuous blood pressure with major events like heart attacks and strokes, we may even develop more accurate models to predict which types of spikes create the most cardiovascular risk.

Totally agree, although perhaps the real gift of this technology will be from the fact that people can be more aware of the underlying conditions (high BP) and tighter feedback loops on how to reduce it / manage it vs. just helping notify about an acute emergency situation.

As I typed the above sentence out, I thought "why not both?". Use the technology to reduce your risk, but in the event that the bad event still happens the notification could save your life.

Re: The science behind on-the-wrist blood pressure tracking

#58

Post by outworlder »

throwup238 wrote: post #21
corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

> However, one thing to be aware of is that you are not used to seeing your BP readings from the entire day. Same thing with those continuous glucose monitors that almost anyone can get and put on their arm now. The vast majority of the data and recommendations we have are for diabetics using regular single use measurements or a proper glucose tolerance test so shortly after the user eats a bowl of rice while wearing…

> There's just not that much data on what the average healthy person's response to blood sugar is, especially when it's continuously monitored.

Chicken and egg situation, no?

People are advised not to use those devices because there isn't much data about them for otherwise healthy people. But if they don't use those devices, there won't be much data.

Re: The science behind on-the-wrist blood pressure tracking

#59

Post by m463 »

corry wrote: post #4

Actually, there is a wrist device called "Aktiia" that's approved for use for continuous BP monitoring with clinical accuracy by the UK and German health authorities (I believe). It's a bit of a pain to get over the pond, but with a shipment-forwarding company + a UK App Store account you can get up and running. I've dabbled a bit with it and it's very close to the cuff measurements. It works by calibrating with thei…

Hmm... I remember reading that cuff blood pressure measurements require your arm to be supported. (and also explains why a lot of blood pressure measurements are inaccurate)

I wonder if you're calibrating on a supported arm, then letting your arm swing free later with the wrist device.

Re: The science behind on-the-wrist blood pressure tracking

#60

Post by throwup238 »

outworlder wrote: post #58
throwup238 wrote: post #21

Earlier quoted context omitted.

> However, one thing to be aware of is that you are not used to seeing your BP readings from the entire day. Same thing with those continuous glucose monitors that almost anyone can get and put on their arm now. The vast majority of the data and recommendations we have are for diabetics using regular single use measurements or a proper glucose tolerance test so shortly after the user eats a bowl of rice while wearing…

> There's just not that much data on what the average healthy person's response to blood sugar is, especially when it's continuously monitored. Chicken and egg situation, no? People are advised not to use those devices because there isn't much data about them for otherwise healthy people. But if they don't use those devices, there won't be much data.

The data has to be collected under clinical conditions to control for confounding variables. People are notoriously bad at accurately recording their precise food intake which is probably the most important variable here. They need to do smaller controlled studies with provided diets. Large scale population studies with sensor data in the wild is going to be a trickier proposition that requires linking the sensors to the rest of the patients medical records which is a privacy mine field.
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