5 Surprising Ways That Sleep Affects the Brain

How Does Sleep Affect the Brain?

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Lack of sleep can take a serious toll on your body, but it can also have a powerful influence on your brain. The amount of sleep we need each night varies from person to person, but the average sleep length is somewhere around 7 to 8 1/2 hours each day.

While the exact reasons why we sleep are still up for debate, experts do know is that sleep deprivation is a very real problem for many people including kids to adults. As people spend more and more time in a wakeful state - for reasons ranging from illness to work schedules to poor sleep habits - they also become increasingly sleep deprived.

A lack of sleep is known to have a wide range of health effects, such as decreased immunity, weight gain, high blood pressure and depression. But what you might not realize is the degree that sleep deprivation can impact your brain. Sleep loss can have very real and sometimes long-term effects on your brain. It can impair your cognitive abilities in the short-term, and some research suggests that such sleep loss might even lead to lasting brain damage.

Let's explore just a few of the different ways that sleep affects your brain.


Institute of Medicine (US) Committee on Sleep Medicine and Research. (2006). Extent and health consequences of chronic sleep loss and sleep disorders: Unmet public health problem. H.R. Colten & B.M. Altevogt (Eds.). Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK19961/.

National Sleep Foundation. (2015). How much sleep do we really need? Retrieved from https://sleepfoundation.org/how-sleep-works/how-much-sleep-do-we-really-need.

1. Sleep deprivation impairs cognitive performance.

Tired student reading a book
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This one probably comes as no surprise, but getting a good night's sleep really does improve your overall cognitive performance including attention, concentration and judgement.

Researchers have demonstrated that sleep deprivation reduces attention on visual and auditory tasks and can significantly slow down reaction times. Such impairments can be critical in high-stakes situations that require a great deal of attention to the environment such as driving a car during a dangerous rainstorm.

According to the National Highway Traffic Safety Administration, nearly 20% of all auto accidents in the United States are caused by driver fatigue. In a 2009 poll conducted by the National Sleep Foundation, a whopping one-third of all respondents admitted to falling asleep behind the wheel of a moving vehicle.


Alhola, P., & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Neuropsyciatric Disease and Treatment. 3(5), 553-567.

2. Sleep helps improve memory.

Young man in front of blackboard
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There has been a well-observed link between sleep and learning, and new research even suggests that sleeping after you learn something new can improve your memory for that material.

By looking at the brains of mice, researchers were able to see that sleep-deprived mice had less dendritic growth than well-rested mice did after a learning task. The dendritic spines that grow at the ends of neurons help promote the transmission of information across the synapse resulting in improved neural communication.

Deep sleep, the research suggests, results in improved learning and causes actual structural changes in the brain.


Yang, G., Lai, C. S. W., Cichon, J., Ma, W., Li, W., & Gan, W. B. (2014). Sleep promotes branch-specific formation of dendritic spines after learning. Science, 344(6188), 1173. DOI: 10.1126/science.1249098.

3. Lack of sleep can damage brain cells.

Brain neural network
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Scientists have long known that sleep deprivation causes short-term cognitive impairment, but recent research suggests that extended periods of wakefulness might result in brain damage. Yes, you read that correctly. Losing sleep can actually damage your brain.

By studying the brains of sleep-deprived mice, researchers were able to see that sleep loss damaged and even killed neurons in critical areas of the brain stem that are involved in the regulation of wakefulness and alertness.


Sexton, C. E., Storsve, A. B., Walhovd, K. B., Johansen-Berg, H., and Fjell, A. M. (2014). Poor sleep quality is associated with increased cortical atrophy in community-dwelling adults. Neurology, 83(11), 967-973. doi: 10.1212/WNL.0000000000000774.

4. Sleep helps clean toxins from the brain.

Woman sleeping
Ray Kachatorian / The Image Bank / Getty Images

A good night's sleep can leave you feeling refreshed, alert and ready to face the day, but researchers have also found another important function of sleep - it helps clean toxins out of the brain. According to a study published in the journal Science, sleep causes brain cells to shrink allowing fluids to wash away and clean up toxins that have accumulated during the previous day.

"The brain only has limited energy at its disposal and it appears that it must choose between two different functional states - awake and aware or asleep and cleaning up," explained researcher Dr. Maiken Nedergaard. "You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time."

This clean-up function, they suggest, might well be one of the primary reasons why we sleep. Since the brain cannot perform these functions while awake and maintain the processes necessary for wakefulness and alertness, we must sleep to allow the brain to clean up after itself.


Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thyagarajan, M., O'Donnell, J.,...Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science. 342(6156), 373-377. DOI: 10.1126/science.1241224.

5. Lack of sleep might shrink your brain.

Sleeping with alarm clock in foreground
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Here's another one that just might shock you - lack of sleep or poor sleep might make your brain smaller.

In a study published in the journal Neurology, researchers examined the brains of 147 adult participants between the ages of 20 and 84. The subjects were given two MRI brain scans approximately 3.5 years apart. They also completed a questionnaire examining their sleep habits including how long it took them to fall asleep at night and how often they used medications to induce sleep.

Around 35% of the participants met the researcher's criteria for poor sleep. Examining the MRI results, the researchers observed that such sleep problems were linked to a faster decline in brain volume including areas such as the frontal, parietal and temporal lobes.

“It is not yet known whether poor sleep quality is a cause or consequence of changes in brain structure,” explained Claire E. Sexton, one of the study’s authors. “There are effective treatments for sleep problems, so future research needs to test whether improving people’s quality of sleep could slow the rate of brain volume loss. If that is the case, improving people’s sleep habits could be an important way to improve brain health."


Zhang, J., Zhu, Y., Zhan, G., Fenik, P., Panossian, L., Wang, M. M., Reid, S., Lai, D., Davis, J. G., Baur, J. A., & Veasey, S. (2014). Extended wakefulness: Compromised metabolics in and degeneration of locus ceruleus neurons. The Journal of Neuroscience, 34(12), 4418-4431; doi: 10.1523/JNEUROSCI.5025-12.2014.

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