DataDave said:

One practical note: write down what you did and when, before you need it.

Agreed, and one caution: a single measurement is not a measurement. Anything that moves day to day needs a trend before it means anything at all.

DataDave said:

One practical note: write down what you did and when, before you need it.

Thank you — that is the clearest version of this I have read, and I have read a lot of them. Sending this to two other people who asked me the same thing last week.

Adding the clinical framing, because it changes how the question reads. Worth answering the question that was asked rather than the one behind it. The narrow version usually has an answer; the broad version usually does not, and answering the broad one is how a thread stops being useful.

KevinCompounds said:

Worth answering the question that was asked rather than the one behind it.

Can confirm. Same sequence, different timescale. I had assumed I was the exception until I read this.

KevinCompounds said:

Worth answering the question that was asked rather than the one behind it.

There is a second half to this that has not been said yet. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.