Commonly used arm positions can overestimate blood pressure readings: study

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.?

Another fun factor I learned about five years ago is temperature. My gym was offering a complimentary fitness evaluation, which among other things included a blood pressure test. The trainer was horrified to see 140-something over something equally terrible, and started explaining how she'd have to refer me to a doctor and advise that I refrain from strenuous physical activity, until I showed her a report from my annual physical a few days prior with 106/70. Turns out that walking to the gym in shorts and a T-shirt in late January causes enough vasoconstriction to really screw with some measurements.

I once had a similar high outlier blood pressure reading after a somewhat busy day followed by running through the city to my blood donation appointment. Who knew that BP is affected by external factors and doesn't stay constant throughout the day‽‽