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> 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 it, it sends them into a hypochondriac spiral when they see a peak of 200. Their doctor generally has to talk them down. 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.

> 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.

One of the things I wish had come out of the Quantified Self movement (which is now so mainstream, it wasn't even mentioned in this article), was a consensus awareness of how to mentally handle fluctuations when recording more data.

We already knew that things like weight fluctuated in normal people (periods, hydration, meals, etc), but many of us are still defaulting to the inaccurate model of slowly-changing measurements recorded 1x/2x a year at the doctor's office.

I'm sure people will get used to it, and many of the weight apps already wisely show averages to discourage fixating on individual measurements, but it feels like a missed opportunity.

From my point of view, that's the whole point of wearing a continuous biometric monitor so that you can see the normal variation. These one off medical tests that people use to make major life and health decisions seems kinda crazy to me.

> However, one thing to be aware of is that you are not used to seeing your BP readings from the entire day. Did you jump in a cold plunge 10 minutes before it ran? Get ready to see a really high reading dot in the 'danger zone'. Went for a jog and are catching your breath on a park bench? High dot.

This is a great point. Blood pressure readings are only useful in the context of stationary measurements under known conditions. Blood pressure is inherently volatile and depends on activity and recent movements, or to extreme events like cold exposure.

There are even finger-cuff blood pressure monitors designed for continuous, constant blood pressure measurement in the context of a lab or hospital setting. Their measurements would be useless in the context of someone moving around all day, but it can be useful in the context of someone under anesthesia or undergoing a controlled lab test.

Anecdotally I find my blood pressure (measured with a regular upper-arm cuff while sitting) to often be lowest soon after completing a workout, like a hard 5K run outside. I'm not sure why, maybe the vasodilation effect from increased nitric oxide production?

IANAM, but if cardiac output is constant (say) and HR ↑ then you would expect BP ↓. I think that indicates good health too, that you don't need increased output, HR is just increasing to move oxygen around faster.

Yes, it indicates good health. Flexible arteries are healthy arteries. If you have high BP at night when sleeping that is very unhealthy. I urge anyone who has high blood pressure readings to get a 24 hour BP monitor to rule out labile hypertension.

> Blood pressure readings are only useful in the context of stationary measurements under known conditions.

This isn't fully true. For clinical reference to known "good" number ranges, then yes, you want to make the comparison as accurate as possible.

Butm there's a lot of potential unlocked with more data.

For example, we could discover that daily BP averages are more predictive than isolated doctor's office measurements. Imagine two people with equal BP measures at the doc's, but one has a more stressful job with higher average BP. We might reasonably expect them to have worse cardiac outcomes. Or consider the person who's anxious about docs and consistently shows higher numbers in the office than outside; we'd expect the reverse!

Another factor might be examining the variance. This already has precedents, since we know there are things that heart rate variability (HRV) correlate with more strongly than heart rate itself.

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-and-play philosophy.

Are the sensors already capable of it? Maybe someone could make a third party app for the watch

+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)

Most people don’t know about this feature on the galaxy watch because it’s only approved in certain countries, though you can hack the SHM to enable it.

Was unaware of the Aktiia. Thank you for posting. I saw firsthand how CGM changed my behavior and would love the same for ketones and blood pressure.

I am particularly excited about the UT Austin research[1] that used conductive temporary tattoos to get actual real time data and not just polling at intervals. However it’s not yet at the stage of commercialization and the design is more the width of a cuff than a watch.

[1] https://scitechdaily.com/electronic-tattoo-offers-highly-acc...

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.

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 my heart rate above 130 which is the highest I could go at that elevation. Obviously I couldn't actually take a reading while moving but I could have it on my wrist, stop and immediately press the button. The pattern I observed was activity raises temperature which lowers blood pressure.

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.

The *only* pattern I could find was it was inversely related to *perceived* temperature. The doc said that relationship was to be expected. My blood pressure would not be elevated even during the recovery period.

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 hopefully give me a better understanding of the condition. For context, I've jumped through all sorts of specialty doctor hoops and there is no known underlying cause outside of the fact that it just showed up after Covid.

Do you or anyone you know happen to have firsthand experience with the device?

I've found similar. I don't know if it was post-Covid, but I have completely asymptomatic high blood pressure. It's really scary to go to the doctor for an extremely routine health check expecting to be back at work in an hour, and then suddenly be told that your blood pressure is so high that you need to go to hospital immediately.

There's no obvious cause, I'm fit and healthy in all other ways, I've had multiple blood tests and ECGs, my cholesterol is normal, everything is normal, just the blood pressure. I also didn't know about this machine but I might get one. I have developed anxiety around having it taken (because of the experience of getting sent to hospital!) so it goes up when I take it, like extreme white-coat syndrome.

I'm definitely getting one of these gadgets so I can see what it really is, without the stress and pain (those things hurt!) of inflating cuffs.

You can request a 24 hour monitor from your doctor.

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.

Thanks for sharing your experience, I appreciate it. What I've seen from the 24h studies I've is very similar to what you describe, BP is highly variable throughout the day and nearly everything you do (or don't do) has an influence on it. One saving grace, if you can call it that, is that BP responds extremely well to medication. I take a small pill every morning and my doc says so long I keep it up, I've nullified all related health risk since my BP is now in a good range. So something to consider if, like me, you never find an underlying reason.

Just curious if you BP was low/normal at night?

Not really, it was usually hovering right around the border of what's considered high blood pressure. As you might guess, the daytime numbers were off the charts compared to that. Luckily my body responds very well to the medication and a small dose is all I need to stay in a good range the whole day.

I have labile hypertension so my BP readings are whack. It is usually up at 160/100 at the doctors office but at home it is normal. Docs did not believe me and were trying to force me onto meds till they put a 24 hour monitor on me. BP spikes and drops during the day and drops to 100/60 at night.

Labile hypertension is the most difficult to treat. So far my heart is perfect for a late 50's dude. Just had an colorflow echocardiogram, no sign of hypertension in the heart. Probably because I eat so much fish.

If I drink coffee my BP is up all day though. I am just very sensitive.

https://en.wikipedia.org/wiki/Labile_hypertension

Funny I had a similar experience, late twenties, felt completely healthy, but was constantly having chest pains. I was a bit over weight at the time but I walked everywhere and was really active, doctors office my BP was always ~ 140/80, he prescribed me meds but I wasn't satisfied with that. I went and got a full heart study done and a 24hr blood pressure monitoring done, my heart and BP are totally fine apparently.

I really freak out about getting my blood pressure taken in a clinical setting, it's really unusual.

I had some treatment for a kidney stone recently, and after the procedure they were checking me with some pretty accurate machines, like 10 times in 24 hours (apparently), 128/80, for some reason in that specific setting I didn't freak out.

White coat HT is a weird thing.

I have frequent chest pains as well since my early 20s! They tell me it is costochondritis but my inflammatory markers are always exceptional. I know what it is now and it is totally neurological, both issues.

Wonder if you have noticed if you were neurologically sensitive to any types of foods?

Eventually they subsided, I don't even remember when, and I've never really had them since...unless I have reflux, which does happen for me occasionally.

I'm learning I just can't really do coffee / caffeine though, I don't think it's ever really been good for me, it causes reflux and anxiety for me, but I just loved coffee to much. I gave up recently however!

You might have heart burn occasionally too ?

I cut out caffeine & my chest pain completely went away & never came back.

I am wondering if continuous blood pressure monitoring would have some knock-on effects as a measurable, correlatable negative health effect of stress.

It would mean that you can literally show that working conditions are shortening your life.

Your company's health insurance could look at BP during commuting hours and in the office vs. at home and raise rates on companies based on their policies.

Unfortunately they get very mixed reviews on Trustpilot, both for the product and for after-sales support:

https://www.trustpilot.com/review/aktiia.com (2.9/5)

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.

What extra useful information can you get from continuous BP measurement compared to once or twice daily measurement?

How specific events throughout the day affect your BP, like things you ate, caffeine, a walk in the cold/heat, exercise, or a conversation. I'd say it's all useful info for perspective on how to manage stress and circulatory health.

I can see how the information can be useful from a big-data perspective (finding correlations between the data of thousands of people), but for individuals I'm not convinced yet. For example, how do you know if a spike in BP is normal, or if it's only happening in your specific case and it needs attention?

I think the best answer to that is ask your doctor if you see something that concerns you. Though, even without an expert opinion or big data as a reference, establishing what is a baseline for yourself and then noting when there is significant deviation can have value. It could be an early warning sign or just encouragement to get help if your BP is one day very high or low. Some googling can probably give you an idea of what are normal ranges based on activity, too.

One real answer is "we don't know because this capability hasn't existed before" I mean, you can wear something like a traditional cuff that puffs itself up every five minutes or whatever, but that doesn't really fit into a patient/subjects life. Good like trying to recruit people for a long term longitudinal study.

But having worked in medical sensors, and spending time with researchers as customers, there was a real sense that they could learn a lot from BP readings that were accurate and continuous.

> Aktiia

Looks interesting, but it too _requires_ a cloud account to function. WTH.

Thanks for pointing that out. I would love to have regular automatic BP measurements but not with closed source software that demands an internet connection.

> 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 reach its lowest sometimes, in state of absolute calm: no movement, no talking, no anxiety. Hence the 'white collar hypertension', i.e. high BP when measured in hospitals and GPs office, where they don't give you enough time to settle down, or are not spaces that induce calm mental states.

The way I take my BP reading is every 5 minutes, until I get a similar reading after 2 consecutive measurements. It takes longer than you'd expect.

During a recent visit, I mentioned my "White Coat Syndrome" was probably affecting me right there, so they selected their most attractive woman with the best perfume and a manual sphygmomanometer for a hands-on measurement, before releasing me.

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.

The cause is actually known: high amounts of fructose or sugar (which is 50% fructose) -> decrease in nitric oxide production in the liver -> high BP

Like many things, it is diet related. It seems "unknown" because GPs are still lagging well behind modern dietary research and are often nothing more than pill pushers. Lowering your sugar and simple carb intake over the long term, and fixing potentially hidden metabolic syndrome (see skinny fat people with unhealthy livers) is how you reverse it.

Hey I hear you, appreciate the perspective but I'm borderline keto most days -- almost zero sugar, very few carbs, etc -- and yet still here.

So while this may explain some amount (perhaps most?) of peoples idiopathic/essential HBP I doubt it's that simple.

"It's your potassium levels", "it's your homocysteine levels", "it's your fructose", "it's white-coat syndrome", "it's...." etc. Surely we're making progress but it's also not a silver bullet thing.

Good thing the treatments are so safe and effective.