Researchers from the University of Cambridge and Fudan University have said that seven hours is the ideal amount of sleep for people in their middle age and upwards, with too little or too much little sleep associated with poorer cognitive performance and mental health.
Sleep plays an important role in enabling cognitive function and maintaining good psychological health. It also helps keep the brain healthy by removing waste products.
By analysing these data, the team found that both insufficient and excessive sleep duration were associated with impaired cognitive performance, such as processing speed, visual attention, memory and problem-solving skills.
Seven hours of sleep per night was the optimal amount of sleep for cognitive performance, but also for good mental health, with people experiencing more symptoms of anxiety and depression and worse overall wellbeing if they reported sleeping for longer or shorter durations.
Disruption to this type of sleep has been shown to have a close link with memory consolidation as well as the build-up of amyloid - a key protein which, when it misfolds, can cause 'tangles' in the brain characteristic of some forms of dementia.
Additionally, lack of sleep may hamper the brain's ability to rid itself of toxins. Having a consistent seven hours’ sleep each night, without too much fluctuation in duration, was also important to cognitive performance and good mental health and wellbeing.
Previous studies have also shown that interrupted sleep patterns are associated with increased inflammation, indicating a susceptibility to age-related diseases in older people.