Biochemist here: I suspect this has more to do with baseline sympathetic/parasympathetic nervous system activity. (I only read the abstract, but I’m surprised they didn’t mention correcting for this.)
So basically it just measures mild dysautonomia like cold hands/feet caused by Upper Airway Resistance Syndrome.
Is that in the paper? Because a priori, I definitely wouldn't ascribe it to that specific a cause, and at least that's not what I meant.