It’s always a relief to climb into bed at the end of a long day, but the exact reason why humans need sleep is still a mystery. For a long time it’s been thought that the brain uses sleep to flush toxins out of the brain and get rid of damaging molecules. However, a new study now suggests that just the opposite may be true, and experts say that being active might be more beneficial for cleaning the brain. A team from Imperial College London’s UK Dementia Research Institute used a fluorescent dye to study the brains of mice, tracking how quickly the dye moved from one area of the brain to another before eventually being cleared. They discovered that the clearance and movement of fluid was markedly reduced during sleep, casting doubt on the long-held belief that sleep clears toxins via the glymphatic system, a mechanism that flushes waste from the brain. On the other side of the study, the brain is shown to be active in flushing toxins when the body is active and exercising. Although the findings still need to be confirmed in humans, the results suggest that exercise is important in preventing dementia.
