A Nightly Cleanup

Deep sleep isn't just rest — it may also be maintenance. Researchers think this is when the brain's glymphatic system works hardest, using channels around its blood vessels to flush away waste proteins that build up during the day, including ones linked to Alzheimer's. Exactly how much sleep boosts this cleanup is still debated — some recent studies even suggest clearance slows while we're under — but the brain's waste-removal plumbing is real, and how it ties to sleep is an active research question.

What's clearer is the long-term pattern. Chronic poor sleep is associated with higher dementia risk later in life — one reason ongoing sleep loss is treated as a real health concern, not just a bad mood.