Each night, the sleeping brain undertakes a quiet act of self-renewal, clearing the molecular residue of waking life — including the proteins implicated in Alzheimer's disease. New research from Edith Cowan University suggests that how effectively this cleansing proceeds is not equal for everyone, but is shaped in part by which variant of the AQP4 gene a person carries. The finding does not change what we know about sleep's importance; it deepens it, suggesting that the same poor night's rest may carry vastly different consequences depending on one's genetic inheritance — and that prevention,