Earlier this year, research published by a number of cognitive neuroscientists pinned down the optimal amount of sleep for adults to 7 hours.

The research - The brain structure and genetic mechanisms underlying the nonlinear association between sleep duration, cognition and mental health - looked at data on 500,000 adults, predominantly white (94%) and of European ancestry. They discovered that for the best cognition and wellbeing, the optimal amount of sleep for adults is a consistent 7 hours every night.

'We found that people who slept that amount performed – on average – better on cognitive tests (including on processing speed, visual attention and memory) than those who slept less or more.'

The research also revealed that the areas of the brain most affected by sleep deprivation are the hippocampus, the brain structure responsible for learning and memory, and the frontal cortex, responsible for emotional regulation. These areas of the brain are also involved in dementia such as Alzheimer's, which supports other evidence that suggests there is a link between sleep duration and the risk of developing Alzheimer's.

Read more on The Conversation: Sleep: here’s how much you really need for optimal cognition and wellbeing – new research