There is a wealth of information supporting the notion that plenty of sleep (typically 7-8 hours each night) is necessary for proper brain function. But how much sleep do we really need? And why is sleep so important for brain activity and overall health?
Let’s take a look at how sleep supports brain health by examining…
- its impact on the physical structures of the brain
- how it supports memory and learning
- how healthy sleep habits can help prevent neurodegenerative disease and cognitive decline as we age
Sleep and Brain Structure
There are two main structural components of brain tissue: gray matter and white matter.
Gray matter is a collection of neuron bodies, including the nuclei of the cells and their dendrites (the portion of the neuron that receives a signal from another neuron), and other supportive cells (called glia).
White matter is a collection of axons, the part of the neuron that sends a signal to another neuron’s dendrites. The structure and total composition of white matter are often used as a measure of overall brain health.
The more white matter in a person’s brain, the better they perform on tasks involving cognition, memory, attention, and executive function (the ability to modulate and control impulsive behaviors).
This distinction is essential in understanding how sleep affects cognition and overall brain health in general. To determine the effects of sleep on brain health, scientists in one study compared groups of people with different sleep patterns. Not only did they study the participants’ performance on cognitive tasks, but they also used imaging techniques (such as MRI) to visualize their brain structures.
People who reported having a high quality of sleep also showed a larger amount of white matter compared to people reporting poor sleep quality (1). As sleep research develops, However, the amount of sleep a person gets seems to matter less. So long as the quality of sleep is sufficient, the number of hours a person sleeps has no apparent effect on the brain’s white matter (2).
Sleep and Memory
Sleep is critical in building and reinforcing long-term memories. Scientists hypothesize that sleep allows the brain to consolidate information learned during the day into long-term memories (3). Disruptions to sleep have been reported to cause problems with memory and cognition (4).
These effects have also been studied in children and adolescents with implications for education that have already transformed schools (5).
Do you remember waking up at an unhealthy hour to ride the bus to school before dawn? Children and teens in many states no longer participate in this absurd ritual, in part due to the dissemination of this information to educational leaders. Children and adolescents perform poorly on cognitive tasks and have problems with memory when sleep patterns are disrupted.
Remember how people with poor sleep quality suffered from reduced white matter? This problem extends to children and makes learning difficult, especially when we consider that most teens follow different typical sleep patterns. They usually fall asleep later in the evening, around 11 pm, but still need up to 9 hours of sleep (6).
Sleep and Aging
One of the greatest benefits of consistently having a good night’s sleep can be realized overtime. Many people experience a decline in memory and cognitive function as they age. Some of this is natural, and some of it is a result of neurodegenerative disease (e.g., Alzheimer’s). Many researchers are looking to find medications that can help alleviate these problems. In contrast, others have linked specific activities like reading or learning a new language with improved cognitive function in old age. However, sleep may also be essential to maintaining a healthy brain in old age.
Getting quality sleep isn’t just important for the aging population. Did you know that the quality of sleep in youth and middle age can actually influence your brain health in old age? (7)
This may be due to the impact of sleep quality on the white matter throughout your life. In maintaining healthy amounts of white matter as a young adult and into middle age, you will be a step ahead in keeping your brain protected against the natural effects of aging.
A Good Night’s Sleep
So, just how much sleep do we really need? Based on the research, the amount of sleep isn’t as important as the quality of sleep a person gets each night.
Having deep, restful sleep with no interruptions promotes the generation and preservation of white matter, which in turn supports memory, learning, executive function, and even reduces the magnitude of cognitive decline that accompanies the aging process.
Want to sleep better? Take a look at these tips to improving your quality of sleep.
- Sexton CE, Zsoldos E, Filippini N, et al. Associations between self-reported sleep quality and white matter in community-dwelling older adults: A prospective cohort study. Hum Brain Mapp. 2017;38(11):5465-5473. DOI: 10.1002/hbm.23739.
- Zitser J, Anatürk M, Zsoldos E, et al. Sleep duration over 28 years, cognition, gray matter volume, and white matter microstructure: a prospective cohort study. Sleep. 2020 [Epub ahead of print]. DOI: 10.1093/sleep/zsz290.
- Antony JW, Paller KA. (2017) Hippocampal contributions to declarative memory consolidation during sleep. In: Hannula D, Duff M. (eds.) The Hippocampus from Cells to Systems. Springer, Cham.
- Morrow EL, Duff MC. Sleep supports memory and learning: implications for clinical practice in speech-language pathology. Am J Speech Lang Pathol. 2020 [Epub ahead of print]. DOI: 10.1044/2019_AJSLP-19-00125.
- Prehn-Kristensen A, Göder R. Sleep and cognition in children and adolescents. Z Kinder Jugendpsychiatr Psychother. 2018;46(5):405-422. DOI: 10.1024/1422-4917/a000614.
- Understanding sleep. raisingchildren.net.au: the australian parenting website. https://raisingchildren.net.au/newborns/sleep/understanding-sleep/about-sleep. Accessed March 28, 2020.
- Scullin MK, Bliwise DL. Sleep, cognition, and normal aging: integrating a half century of multidisciplinary research. Perspect Psychol Sci. 2015;10(1):97-137. DOI: 10.1177/1745691614556680.