Humans have been wondering why we sleep for thousands of years. Is sleep’s purpose rest and relaxation, memory consolidation or maybe cognitive processing? In the last 15 years, scientists have discovered another possible explanation – waste disposal. In 2012 neuroscientist Maiken Nedergaard’s lab discovered that the brain has its own cleaning process, the glymphatic system, which clears away unhelpful proteins and metabolic byproducts, and only switches on at night. Since that groundbreaking discovery we’ve learned more about what drives this system and, importantly, how it could be impacting dementia. To understand more, Ian Sample talks to Prof Nedergaard about how she made the original discovery and how subsequent work is building a picture of sleep as anything but a quiet and inactive state. Help support our independent journalism at <a href="https://www.theguardian.com/sciencepod">theguardian.com/sciencepod</a>
