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330 points wglb | 1 comments | | HN request time: 0.268s | source
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crazygringo ◴[] No.41841006[source]
There's definitely a huge variance in blood pressure readings depending on posture, relaxation, arm position, recent activity, etc. If you buy a blood pressure monitor, it's really interesting to see how "random" a single reading at the doctors' is, and how large your fluctuation throughout the day is.

That being said, it really makes me wonder about studies that correlate blood pressure with other things. Is the blood pressure really being measured "correctly" in all those studies? Or not?

In other words, if your "true correct" blood pressure is lower than what the doctor normally takes, but then a lot of the studies are based on real-life "incorrect" higher blood pressures, then don't you similarly want an "incorrect" higher reading for consistency? Or are the studies always really done with far more accurate blood pressure readings, where the patient sits still for 5 min beforehand, keeps their legs uncrossed, is totally free of stress and anxiety, didn't exercise beforehand, etc.?

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1. makeitdouble ◴[] No.41842512[source]
Reading around (e.g. [0]) it sounds like variance isn't something researchers care for, probably with the assumption that screening with a higher value is better than missing an issue from a lower value.

We see the same for body temperature (speed and convenience is usually prioritized over accuracy) and weight (2% variation is largely accepted). Afterall guidelines are already off as by definition, as they don't account for individual circumstances, so perhaps aiming for accuracy is useless in most settings.

[0] https://www.mayoclinic.org/diseases-conditions/high-blood-pr...