Commonly used arm positions can overestimate blood pressure readings: study

I've never looked into research on this subject, but I always assumed this was already well established and known - and it was definitely somewhat already either known or at least believed to be the case:

- Every doctor in the UK I've ever seen do a BP test has made sure the patient's arm is in the right position, rested on a table/cushion if needed, in a way that matches the findings in this study (and while I've only needed my own BP tested once or twice, I've sat in on many, many doctors while they tested the BP of family members of mine).

- My home BP device is a Braun wrist cuff (and is at least a few years old), which has a built in feature that uses an accelerometer to guide you to raise your arm until it's at an angle which means your wrist is at the same level as your heart (this one: https://www.cora.health/guide/best-blood-pressure-monitor/#1... )

I've used the Braun wrist cuff, and while the heart-level feature is cool and perhaps good enough to mitigate position issues, I found that it was very unreliable vs. cuff measurements.

What do I mean by "unreliable"? Two things - (1) internally consistency for the given device and (2) not closely correlated to the arm cuff measurements.

My method: I would wear both devices and take a series of readings (like 5+ from each in a session, and did multiple sessions a day).

My results: while the cuff readings of course had some minor variation in of themselves, they were largely consistent with themselves (i.e. clustered around the average for the session) whereas the properly-positioned (according to the heart height feature) wrist measurements were all over the place showing big swings between readings and a wider dispersion from the mean.

Then there was the issue of did the wrist average measurements roughly correlate to the cuff averages - and not only was the answer "no", it would vary whether it was higher or lower. Which is a shame - it's ok if it was, say, overstating things by +5 mmHg but overstating at that rate consistently (because then you could mentally adjust the outputs); but when it's inconsistent you're just left scratching your head.

As I wrote about in another thread, the continuous wrist monitor Aktiia that I've been trying gets correlated explicitly to an arm cuff and seems far, far more accurate and consistent than this Braun device. It uses optical imaging of your wrist's blood vessels vs. physical pressure on a cuff.

All this to say - test for yourselves! Try multiple arm cuffs, even. While the exact numbers are less important than the trend, you need a device that you can trust w.r.t. output.