Why Do We Need To Sleep At Night? The Three Functions of Sleep

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Getting a good night’s rest has been shown to improve memory, increase attention, enhance creativity, and aid in decision-making.

-Dr. Jason Holland, Lifespark

3 min read

One might assume that a question as basic as ‘Why do we need to sleep at night?’ was long ago answered by modern science, but the reality is that we’re still learning about the functions of sleeping.  

And if you step back and really think about it, sleep is a pretty weird ritual that we perform every night.

As the comedian, George Carlin, observed, “People say, ‘I’m going to sleep now,’ as if it were nothing. But it’s really a bizarre activity. ‘For the next several hours, while the sun is gone, I’m going to become unconscious, temporarily losing command over everything I know and understand. When the sun returns, I will resume my life.’”

On the surface of it, sleep would seem to confer an evolutionary disadvantage. After all, it’s pretty hard to defend yourself against potential predators when you’re unconscious and have lost command of your body.

Yet, scientists are hard-pressed to identify an animal species that doesn’t need sleep. And extreme sleep deprivation has been shown to be fatal in animals.

So there must be some good reason(s) why we need to sleep at night. Though it’s still an unraveling mystery, recent science has provided some answers.

Here are three of the leading ideas about the functions of sleep:   

1. Sleeping to Conserve Energy.

Sleep helps animals save energy, which may be a particularly important function when food resources are limited. And indeed metabolism does slow down during sleep. Our body temperature drops, and we have less need for caloric intake.

2. Sleeping to Restore the Body.

Sleep also appears to help us rejuvenate after a long day of activity. Notably, many of the body’s restorative functions occur primarily during sleep, such as tissue repair and muscle growth.

3. Sleeping to Boost Brain Plasticity.

Sleep appears be beneficial for the brain in a variety of ways. Specifically, getting a good night’s rest has been shown to improve memory, increase attention, enhance creativity, and aid in decision-making.

This week, we examine the importance of sleep further. 

Tomorrow, we explore the role of dreams and discuss their meaning in our lives. Then on Wednesday, you can self-assess your sleep habits and get personalized feedback based on your responses.

And for those who have bad dreams, Thursday’s piece focuses on ways to minimize the negative impact of nightmares. We then end the week on Friday with a discussion on dreams about lost loved ones and ways to work productively with them.

So, come back each day this week for more on the importance of sleep. And in the comments below, tell us about the role of sleep in your life. What is your relationship with sleep? How does it affect your waking life?


Further Reading:







Assefa, S. Z., Diaz-Abad, M., Wickwire, E. M., & Scharf, S. M. (2015). The functions of sleep. AIMS Neuroscience, 2, 155-171.

Cirelli, C., & Tononi, G. (2008). Is sleep essential? PLoS Biology, 6, e216.

During, E. H., & Kawai, M. (2017). The functions of sleep and the effects of sleep deprivation. In Mitchell G. Miglis (Ed), Sleep and Neurologic Disease (pp. 55-72). London, UK: Elsevier.

Franken, P., Kopp, C., Landolt, H. P., & Lüthi, A. (2009). The functions of sleep. European Journal of Neuroscience, 29, 1739-1740.

Zielinski, M. R., McKenna, J. T., & McCarley, R. W. (2016). Functions and mechanisms of sleep. AIMS Neuroscience, 3, 67-104.


One thought on “Why Do We Need To Sleep At Night? The Three Functions of Sleep

  • November 7, 2018 at 11:03 am

    If sleep is so important, I wonder why it becomes so illusive as we age. I would love to get a restfull night’s sleep, but it seldom happens no matter how much “sleep hygiene” I employ.


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