Science doi:10.1126/science.1180962 (2009)

Sleep in mice affects the formation of amyloid-β plaques — the protein clumps found in the brain in Alzheimer's disease.

David Holtzman from Washington University in St Louis, Missouri, and his colleagues measured amyloid-β levels every hour in the brains of mice engineered to express a mutant form of the human APP gene, which codes for the amyloid-β precursor. They found that amyloid-β levels rose when the animals were awake and fell when they slept. Normal mice and humans showed similar patterns.

When the authors deprived the mice of sleep, amyloid-β levels increased by 20–25%. When they blocked a neurotransmitter that induces wakefulness, they saw lower amyloid-β levels and fewer plaques.