The Overnight Batch Run: what REM sleep does with yesterday Banks do their most important work overnight. The branches close, the batch run reconciles the day’s transactions, and by morning the books balance. Y

our brain does something remarkably similar, and most of us treat it as optional. In this episode I dig into REM sleep, the strange, dream-filled stage stacked into the last few hours of the night. It turns out to do far more than dream. A Berkeley brain-scanning study found that REM takes the emotional charge out of the day before, which is why a short or broken night leaves you carrying yesterday’s stress into today.

Large long-term studies have also linked less REM to higher dementia risk and earlier death.

I go through what those studies do and don’t show, what my WHOOP can and can’t tell me, and what Seneca worked out about all this two thousand years ago. Then the practical bit: three things to try tonight, starting with the one nobody wants to hear about the nightcap.