As much as we know about what happens during sleep, why we actually need to spend several hours slumbering each night is surprisingly less clear.
Many of you might already be thinking: I sleep because I’m tired and need to recuperate. And this is almost certainly true, but over the course of eight hours’ shut eye the amount of energy saved is perhaps less than you’d expect – around 50 kcals or the same as eating half a banana.
Another explanation is that sleep is an evolutionary function designed to keep us out of harm’s way during the dark nights, when in the past we would have been more exposed to attacks from predators and dangerous accidents.
Further theories suggest sleep is primarily about rehabilitation, as many of the body’s restorative functions – muscle growth, tissue repair and protein synthesis – occur mostly when we are asleep.
A more recent idea is that sleep gives the brain its best chance to consolidate memories, with the REM phase playing a significant role in developing our recollections.
So, despite all of these theories, the question remains why?