I have been sleeping much better than usual. Sharp easy-to-notice improvement. After the first time this happened I made a list of 9 possible reasons (lifestyle changes that might have been responsible). I later added one I’d overlooked: standing on one foot to exhaustion a few times.
Yesterday I stood on one foot to exhaustion four times, twice in the morning and twice in the evening. It took about three minutes each time (12 minutes total). Didn’t make any of the nine other candidate changes. And I slept much better than usual. So it is beginning to look like just that one factor is responsible. The one I almost forgot but also the one that seemed most plausible after i remembered it.