Dr.PainCLE said:

Almost every unanswerable question in these threads is unanswerable because three things changed in the same fortnight, and no amount of subsequent…

This is my experience too, for whatever a second data point is worth. Nothing to add that would improve it.

Clinical perspective, offered as context rather than as advice. 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.

Dr.NephBHM_UK said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Mine went the same way, slower.

Dr.NephBHM_UK said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Adding the part of the answer the thread has not reached. Whatever the answer turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, and invite the correction. That is slower than asserting, and it is the only version that survives being wrong.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

Moderator note: the sourcing question belongs in the vendor section and has been split out. No action needed from anybody.