Why We Sleep (And Why It’s So Important to Sleep Well)

by | Last updated May 30, 2024

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Everyone knows it’s important to get a good night’s sleep, but do you know why we need to sleep in the first place?

When you’re asleep, you’re largely unaware of what’s happening around you until you wake up. However, sleep isn’t a passive process where you just close your eyes, fall asleep, and wake up in the morning. Each night, your brain and your body are working hard to keep you firing on all cylinders— all while you catch your forty winks. 

So let’s take a look at why we sleep, and more importantly, why it’s critical that you sleep well each night.

Why Do We Sleep?

Just like eating or breathing, sleeping is an important biological process that not only keeps you alive, but it keeps you healthy. By getting sufficient sleep every night, you’re ensuring that both your body and your mind are healthy, alert, and ready to take on life’s challenges. However, if you don’t get the good sleep you need, you may find yourself feeling sluggish, less alert, and even more likely to get sick or injured.

This is because sleep is essential for helping you recover from the day while preparing you for the next. 

Here are just a few of the processes that happen while you sleep:

  • Boosting your immune system
  • Maintaining brain health, brain function, and brain plasticity— your brain’s ability to create and form memories and react to day-to-day life
  • Regulating your appetite and your sex drive
  • Producing vital hormones like cortisol, leptin, and ghrelin
  • Muscle and tissue growth
  • Repairing or regrowing any damaged cells, including muscle and tissue cells
  • Regulating your mood and mental health

Related: How Sleep Affects Your Hormones

What Makes You Sleep?

Your sleep cycle is controlled by two systems in your body— your circadian rhythm, and your sleep drive. Whether you are a morning person or a night owl, both these systems follow a set schedule to make sure you get the right amount of sleep each night. These schedules can vary from person to person, and change as you age.

Your sleep drive— also called sleep-wake homeostasis— functions similarly to hunger. When you need to eat, your body drives you to find food and eat. When you’re tired and have been awake for a certain length of time, your sleep drive pushes you to sleep. 

So what’s the difference between the drive to eat and the drive to sleep? Unlike hunger, your body can force you to fall asleep if you’ve been awake for too long, no matter where you are or what time it is.

Your circadian rhythm controls your body’s sleep-wake cycle. Unlike your sleep drive, which is affected by time, your circadian rhythm is affected primarily by the sun. In the morning, it signals your brain to produce less melatonin to help you wake up, and signals it to produce more melatonin during the evening to help you sleep.

The sun isn’t the only light source that can affect your circadian rhythm, however. It can be negatively affected by the blue light produced by electronic devices like smartphones, tablets, and even artificial lighting. 

So if you like to use your electronic devices in the evening, you can take precautions to make sure your sleep doesn’t suffer. For instance, you can use blue light blocking products like the products from Swanwick Sleep or Ocushield.

Once your circadian rhythm and sleep drive have prepared you for a good night’s sleep, your brain begins its normal processes to help prepare you for the next day.

What Your Brain Does While You Sleep

Sleep is a much more complicated process than you may expect! But knowing how to use your sleep cycle is key to getting better sleep and waking up feeling refreshed. Let’s take a look at how it works.

Each night while you’re asleep, your sleep cycle alternates through 4 different sleep stages. Each sleep stage consists of either non-rapid eye movement or non-rem sleep, and rapid eye movement (REM) sleep. For every three stages of non-rem sleep, you have a single stage of REM sleep.

The cycle looks like this:

  • Stage 1: This first stage of non-rem sleep lasts for about 7 minutes, and occurs when you first fall asleep. When you first fall asleep, your heart rate, eye movement, and brain activity all slow down.
  • Stage 2: Right before your body enters deep sleep, body temperature drops, and your brain waves briefly spike before they slow. Your brain forms new memories during this sleep stage.
  • Stage 3: The final stage of NREM sleep before you enter REM sleep. This is where your deepest, most restorative sleep takes place, as well as cell and tissue restoration. Your eye and muscle movement stop, and your brain activity slows even further.
  • Stage 4: This stage of REM sleep occurs approximately 90 minutes after you first fall asleep. Your eyes move quickly from side to side— hence “rapid eye movement sleep.” Your heart rate, breathing, and brain activity increase during this sleep stage.

Why Is Sleep Important?

Now that we’ve covered why we sleep, it’s good to touch on why sleep is important. We often take sleep for granted because it’s something we all do, but do well is something entirely different. 

As you’ve likely determined from the nuanced and complex process described above, our body moves through a series of sleep stages in order to perform the processes listed earlier. Improved healing, enhanced immune function and elevated mood are just a few of the benefits you reap from getting sleep (especially good sleep).  

If you’re experiencing chronic sleep issues it can prevent you from getting the quality nightly sleep you need to keep yourself healthy. 

What few people realize is that after just one night of insufficient sleep, you’ll feel the negative effects that sleep deprivation has on your body and your mind.

Here are signs that you’re sleep-deprived:

  • Memory problems, including difficulty remembering things
  • Brain fog
  • Changes in mood, such as increased stress, irritability, and anxiety
  • Daytime sleepiness or fatigue

Poor sleep can impact your immune system as well, increasing your chances of getting sick. Not getting enough sleep can also worsen health problems like high blood pressure, heart disease, and depression. You’re also at greater risk of being injured in an accident when sleep deprived.

Being sleep-deprived can also clutter your mind with information you don’t need, adding to the brain fog and confusion. This is because while you sleep, your brain flushes out excess amounts of a protein called beta-amyloid. When this protein builds up to an excessive level, it creates plaques that can hinder how well your brain cells work, and can eventually even kill them off if there is too much.

Researchers believe that a build-up of this protein from insufficient sleep may be a potential cause of Alzheimer’s Disease and dementia.

Related: Alzheimer’s and Sleep: How Poor Sleep Can Put You At Risk

How Much Sleep Do You Need Each Night?

Beyond quality sleep, an important aspect of sleep is simply getting enough sleep. 

So how much sleep do I need

There isn’t a one size fits all approach when answering this question. Your sleep needs change as you age. 

As a general rule, the younger you are, the more sleep you will need. Here are the recommended hours of sleep needed for each age group, as recommended by the Centers for Disease Control and the experts here at the Sleep Centers of Middle Tennessee:

  • Newborns up to 3 months old need 14 to 17 hours of sleep
  • Infants between 4 and 12 months old need 12 to 16 hours of sleep every 24 hours, including naps
  • Toddlers between 1 and 2 years old need 11 to 14 hours of sleep every 24 hours, including naps
  • Preschool-age children between ages 3 and 5 need 10 to 13 hours of sleep, including naps
  • School-age children between ages 6 and 12 need 9 to 12 hours of sleep
  • Teenagers between 13 and 18 need 8 to 10 hours of sleep each night
  • Adults ages 18 and above need 7 to 9 hours of sleep each night

If you wake up feeling exhausted in the morning, even after a full night’s sleep, then that’s a sign that you’re not getting the high-quality sleep you need. If this is the case, then it’s extremely likely that you have an underlying sleep disorder ruining your rest.

Do You Have a Sleep Disorder?

It’s not always easy to tell if you have a sleep disorder. In fact, many people don’t even realize they have one unless their sleep partner notices their symptoms. A few notable sleep disorder symptoms you or your sleep partner should be aware of include:

  • Taking 30 minutes or more to fall asleep each night
  • Waking up earlier than you intend, or waking up more than once during the night
  • Loud snoring that can be heard outside your bedroom, or gasping during sleep
  • Feeling tired or unrefreshed, even if you got a full night’s rest
  • A dry or sore throat in the morning

Sleep disorders like insomnia, obstructive sleep apnea, or circadian rhythm disorders can have an immense impact on your health and well-being, especially if you’re not aware that you have one. Not only can they cause poor quality, deficient sleep, but they can worsen conditions like diabetes and heart disease, while making you more likely to experience a heart attack, stroke, or chronic pain.

Sleep disorders will not go away on their own— they require consistent, specific treatment so that you can get the restful sleep you need to perform well each day.

Knowing why we sleep makes it all the more important to strive for restful sleep every night. So much of our health is connected to a good night’s sleep that sleep loss or poor sleep quality should never be ignored. 

So if you’re struggling to get the rest you need, better sleep may be just a consultation away. Contact us today at the Sleep Centers of Middle Tennessee to start getting back to the good night’s sleep you deserve.


“Brain Basics: Understanding Sleep.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, www.ninds.nih.gov/disorders/patient-caregiver-education/understanding-sleep.

Brinkman, Joshua E. “Physiology of Sleep.” StatPearls [Internet]., U.S. National Library of Medicine, 24 Sept. 2021, www.ncbi.nlm.nih.gov/books/nbk482512/.”CDC – How Much Sleep Do I Need? – Sleep and Sleep Disorders.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 2 Mar. 2017, www.cdc.gov/sleep/about_sleep/how_much_sleep.html.

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