Poor sleep may accelerate brain changes linked to Alzheimer's disease in people carrying specific genetic variants, according to a new study published in Alzheimer's & Dementia. The AQP4 gene helps regulate fluid movement in the brain and supports the brain's natural waste-clearing system, which becomes most active during sleep. The researchers examined 13 common AQP4 gene variants, along with participants' self-reported sleep habits, brain MRI scans, and cognitive test results. They found that people carrying certain AQP4 variants experienced faster loss of grey matter when they reported shorter sleep duration. Some gene variants appeared to make poor sleep more harmful, while others showed different patterns of brain and cognitive change.