Exactly, this is my concern as well. They say you have to be seated for 5 minutes at least, completely relaxed, not hungry, not having to go the bathroom, in a quiet a room, it must not be too hot or too cold, with both your feet on the ground, before you can have your blood pressure measured, otherwise the reading could be 'artificially' high. Really? It seems to me that if you do all these preparations, the reading will be artificially low, since such conditions are nothing like the conditions that you'll typically find yourself in through the day in your everyday life.
The goal is to get a clinically relevant measurement, captured at rest under specific conditions, not a measurement that's representative of a random moment during everyday life.
We're also treating people for things like blood pressure somewhat statistically rather than individually.
The studies say, people who have a blood pressure measured this way, that is above X, have an N% higher chance of dying M years sooner of A, B or C than people who measure under Y. If you treat with medication Q it lowers blood pressure, measured this way, by Z points, increasing lifespan by W QALY.
Are you treating people who don't need to be treated and missing people who do? Could you achieve better results with continuous, invasive blood pressure measurements while the patients engage in every day life?
Probably, but then you're increasing the cost of both the study and the public health intervention exponentially for gains in the margin.
But if the measurement isn't representative of your actual blood pressure what's the point of taking it? It's completely non-informative. Another problem is that even under very controlled conditions, I sometimes find big differences in blood pressure from one minute to the next.
