https://www.npr.org/sections/shots-health-news/2024/06/26/g-s1-6177/brain-waste-removal-system-amyloid-alzheimer-toxins

About 170 billion cells are in the brain, and as they go about their regular tasks, they produce waste — a lot of it. To stay healthy, the brain needs to wash away all that debris. But how exactly it does this has remained a mystery.

Now, two teams of scientists have published three papers that offer a detailed description of the brain’s waste-removal system. Their insights could help researchers better understand, treat and perhaps prevent a broad range of brain disorders.

The papers, all published in the journal Nature, suggest that during sleep, slow electrical waves push the fluid around cells from deep in the brain to its surface. There, a sophisticated interface allows the waste products in that fluid to be absorbed into the bloodstream, which takes them to the liver and kidneys to be removed from the body.