You know you’re not getting enough sleep, but science is here to back it up

Most of us struggle to think well after a bad night’s sleep – we feel foggy and fail to perform at our usual level at school, college or work. You may notice that you aren’t concentrating as well or your memory doesn’t seem up to par. However, decades of poor sleep can potentially lead to cognitive decline.

Poor sleep also affects people’s moods and behavior, whether young children or older adults. So how much sleep does our brain need to function properly in the long term? Our new research study, published in natural agingprovides an answer.

Sleep is an important part of maintaining normal brain function. The brain reorganizes and recharges during sleep. In addition to eliminating toxic waste byproducts and boosting our immune system, sleep is also essential for “memory consolidation,” during which new memory segments based on our experiences are transferred into the long-term memory.

An optimal quantity and quality of sleep allows us to have more energy and better well-being. It also allows us to develop our creativity and thinking.

Examining babies from three to 12 months old, researchers have noted that better sleep is associated with better behavioral results in the first year of life, such as being able to adapt to new situations or to regulate emotions effectively.

These are important building blocks for cognition, including “cognitive flexibility” (our ability to easily change perspective) and are linked to well-being later in life.

Sleep regularity appears to be linked to the brain’s “Default Mode Network” (DMN), which involves regions that are active when we are awake but not engaged in a specific task, such as resting while our mind vagabond. This network includes areas that are important for cognitive functionsuch as the posterior cingulate cortex (which deactivates during cognitive tasks), the parietal lobes (which process sensory information) and the frontal cortex (involved in planning and complex cognition).

There are signs that, in adolescents and young adults, poor sleep may be associated with changes connectivity within this network. This is important because our brain are still in development in late adolescence and early adulthood.

Disruption of this network can therefore have knock-on effects on cognition, such as interference with concentration and memory-based processing, as well as more advanced cognitive processing.

Alterations in sleep patterns, including difficulty falling asleep and staying asleep, are important features of the aging process. These sleep disorders are highly plausible contributors to cognitive decline and psychiatric disorders in the elderly.

Get the right amount

Our study aimed to better understand the link between sleep, cognition and well-being. We found that both insufficient and excessive sleep contributed to impaired cognitive performance in a middle-aged to elderly population of almost 500,000 adults in the British Biobank. However, we haven’t studied children and adolescents, and because their brains are developing, they may have different requirements for optimal sleep duration.

Our main finding was that seven hours of sleep per night was optimal, with more or less of that providing less benefit for cognition and mental health. In fact, we found that people who slept as much did – on average – better on cognitive tests (including processing speed, visual attention and memory) than those who slept less or more. Individuals also need seven hours of sleep consistently, without much fluctuation in duration.

That said, we all react slightly differently to lack of sleep. We found that the relationship between sleep duration, cognition and mental health is influenced by genetics and brain structure. We noted that the brain regions most affected by sleep deprivation are the hippocampus, well known for its role in learning and memoryand areas of the frontal cortex, involved in the top-down control of emotions.

But while sleep can affect our brains, it could also work the other way around. It could be that age-related shrinkage of brain regions involved in regulating sleep and wakefulness contributes to sleep problems later in life. It can, for example, decrease production and melatonin secretion, a hormone that helps control the sleep cycle, in older people. This finding appears to support other evidence suggesting that there is is a link between sleep duration and the risk of developing Alzheimer’s disease and dementia.

While seven hours of sleep is optimal for protecting against dementia, our study suggests that getting enough sleep may also help alleviate dementia symptoms by protecting memory. This highlights the importance of monitoring sleep duration in elderly patients with psychiatric disorders and dementia to improve their cognitive functioning, mental health and well-being.

So what can we do to improve our sleep for optimal cognition and well-being in our daily lives?

A good start is to ensure that your bedroom temperature and ventilation are good – they should be cool and airy. You should also avoid drinking too much and watching thrillers or other exciting content before going to bed. Ideally, you should be in a calm, relaxed state when trying to fall asleep. Thinking about something nice and relaxing, like the last time you were on the beach, works for a lot of people.

Technological solutions such as apps or wearable devices can also be beneficial for mental health as well as for tracking sleep and ensuring sleep duration consistency.

To enjoy life and function optimally on a day-to-day basis, you may want to monitor your own sleep patterns to ensure that you are getting seven hours of sleep on a regular basis.


Barbara Jacquelyn Sahakianprofessor of clinical neuropsychology, University of Cambridge; Christine LangleyPostdoctoral Researcher, Cognitive Neurosciences, University of Cambridge; Jianfeng Fengscience and technology teacher for brain-inspired intelligence, Fudan Universityand Wei Chengyoung principal researcher in neuroscience, Fudan University

This article is republished from The conversation under Creative Commons license. Read it original article.

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