In 2013, Dr Maiken Nedergaard, a neurologist at the University of Rochester in New York, published an article in the journal, ‘Science’ which described sleep as a waste removal system for the brain. The study showed that brain cells shrink during sleep to open up gaps between neurons and allow fluid to wash the brain clean. Dr Nedergaard said, ‘The brain only has limited energy at its disposal and it appears that it must choose between two different functional states – awak