It’s no secret that sleep is one of the most important activities for good health. When we sleep, our bodies take time to:

  • repair muscles
  • grow bones
  • manage hormones
  • sort memories

There are four stages of sleep, consisting of both REM and non-REM sleep, that we cycle through each night.

In this article, we will explore these stages of sleep, discuss sleep disorders, plus tips for getting better sleep.

There are two types of sleep: REM — or rapid eye movement — sleep and non-REM sleep. Non-REM sleep consists of multiple stages, while REM sleep is just a single stage.

Stage 1

This stage of non-REM sleep happens when you begin to fall asleep and generally lasts only a few minutes.

During this stage:

  • heartbeat and breathing slow down
  • muscles begin to relax
  • you produce alpha and theta brain waves

Stage 2

This next stage of non-REM sleep is a period of light sleep before you enter deep sleep, and it lasts for roughly 25 minutes.

During this stage:

  • heartbeat and breathing slow down further
  • no eye movements
  • body temperature drops
  • brain waves spike up and down, producing “sleep spindles”

Stages 3 & 4

These final stages of non-REM sleep are the deepest sleep stages. Stages three and four are known as slow wave, or delta, sleep. Your body performs a variety of important health-promoting tasks in these final non-REM stages.

During these stages:

  • arousal from sleep is difficult
  • heartbeat and breathing are at their slowest rate
  • no eye movements
  • body is fully relaxed
  • delta brain waves are present
  • tissue repair and growth, and cell regeneration occurs
  • immune system strengthens

Stage 5: REM sleep

The rapid eye movement stage occurs about 90 minutes after you fall asleep, and is the primary “dreaming” stage of sleep. REM sleep lasts roughly 10 minutes the first time, increasing with each REM cycle. The final cycle of REM sleep usually lasts for roughly 60 minutes.

During this stage:

  • eye movements become rapid
  • breathing and heart rate increases
  • limb muscles become temporarily paralyzed, but twitches may occur
  • brain activity is markedly increased

When you fall asleep at night, you cycle through all of these stages of sleep multiple times – roughly every 90 minutes or so.

For something so necessary to our health and well-being, there’s still so much we don’t know about sleep. However, here are seven fun facts that we do know:

  1. Human beings spend 1/3 of their lives sleeping, while cats spend roughly 2/3 of theirs asleep. Other animals, such as koalas and bats, can sleep up to 22 hours a day.
  2. Newborn babies need roughly 14 to 17 hours of sleep per day, while teenagers require about 8 to 10 hours each night. Most adults need 7 to 9 hours of sleep.
  3. Sleep deprivation can have a hugely negative impact on health. Even as little as 72 hours without sleep can cause mood swings, difficulty functioning, and altered perception.
  4. Energy levels naturally dip at two distinct times of the day: 2:00 a.m. and 2:00 p.m. This explains the post-lunch fatigue that some people feel during the middle of the day.
  5. Dreams can appear in color or entirely in greyscale. One study from 2008 found that access to black and white television has an impact on the color of one’s dreams.
  6. Higher altitudes can have a negative impact on sleep quality. According to research, this may be because of a reduced amount of slow wave (deep) sleep.
  7. Although there’s still much to learn about sleep, the biggest thing we know is that sleep is just as crucial to good health as nutrition and exercise.

According to the American Sleep Association, roughly 50 to 70 million adults in the United States have a sleep disorder. Sleep disorders can have a negative impact on sleep quality, which in turn can lead to other health problems. Below, you will find some of the most common sleep disorders and how they are treated.


Insomnia is a chronic sleep condition characterized by difficulty sleeping. Some people have trouble falling asleep, others are unable to stay asleep, and some have trouble with both. Insomnia often causes excessive daytime sleepiness and fatigue.

Cognitive behavioral therapy (CBT) is the primary treatment for insomnia. CBT may also be combined with sleep medications, which are able to help people fall asleep and stay asleep. For some people, improving sleep hygiene may also help.

Sleep apnea

Obstructive sleep apnea is a condition in which the body stops breathing during sleep. These periods of no breathing, called apnea, happen because the airways of the throat become too narrow to allow air flow. Like insomnia, this condition can negatively affect sleep quality.

The first line of treatment for sleep apnea is a continuous positive airway pressure (CPAP) machine. The CPAP creates enough airflow to allow a person with sleep apnea to breath properly during sleep. If the CPAP does not help, bilevel positive airway pressure (BiPAP or BPAP) is the next option. In severe cases, surgery may be necessary.

Restless leg syndrome

Restless leg syndrome (RLS) is a neurological disorder that causes an uncomfortable feeling in the legs, which often appears when resting or trying to sleep. People with RLS often have trouble getting enough sleep because of their symptoms.

Some medications, such as sleep aids and anticonvulsants, can be prescribed to help manage RLS symptoms. Practicing good sleep hygiene can help relax the body before bed and make it easier to fall asleep.

Shift work disorder

Shift work disorder is a condition that commonly affects those who work outside of a regular 9-to-5 schedule. This disorder can cause an imbalance in the natural circadian rhythm, or sleep-wake cycle. People with this disorder are at a higher risk for increased daytime sleepiness and health issues.

Treatment for shift work disorder includes taking frequent naps, avoiding stimulants, and reducing the number of hours worked, all of which can help promote good sleep quality. For people who sleep during the day, it can also help to use light-blocking tools such as glasses or curtains.


Narcolepsy is a nervous system disorder that causes extreme daytime drowsiness and “sleep attacks”, or sudden bouts of sleep. Narcolepsy also causes cataplexy, which is a sudden, physical collapse caused by loss of muscle control. People with narcolepsy often experience extreme disruptions in their daily life.

Medications such as stimulants and SSRIs are used to treat the symptoms of narcolepsy. At-home treatments, such as avoiding stimulants and exercising regularly, can help to promote healthful sleep. Lifestyle changes, such as avoiding certain activities and making accommodations, are also important to help limit injuries.

Practicing good sleep hygiene is the best way to get quality sleep at night. Here are some ways you can improve your sleep hygiene:

  • Spend time outside in the sun during the day. Exposing your body to natural light during the day can help maintain a healthy circadian rhythm.
  • Exercise or move your body throughout the day. Getting at least one exercise or movement session in each day is a great way to improve your sleep quality.
  • Limit your nap time to no more than 30 minutes. While there are benefits to napping, if you nap for longer than 30 minutes, it can leave you wide awake when it’s finally time for bed.
  • Avoid stimulants and certain foods before bed. Caffeine, nicotine, or alcohol before bed can interrupt your sleep, as can foods that cause indigestion or stomach upset.
  • Limit your screen time an hour before sleeping. TVs, phones, and other electronic devices emit blue light, which can interrupt the hormones that help you fall asleep.
  • Create a comfortable bedroom environment. Investing in a high-quality mattress, pillow, and blanket, as well as other relaxing bedroom items, can help you sleep better.

Incorporating these tips slowly over time can greatly improve your sleep quality. However, if you’re still having trouble falling or staying asleep, it may be time to visit a doctor to discuss more options.

Your body cycles through five stages of sleep each night: four stages of non-REM sleep and one stage of REM sleep. During these sleep cycles, our breathing, heart rate, muscles, and brain waves are all affected differently.

Getting enough sleep is important for health-promoting activities such as digestion, growth, and memory. Certain sleep disorders, like insomnia, can cause poor sleep quality and difficulty functioning throughout the day.

The best thing you can do to improve your sleep quality is to address any underlying conditions and work on your sleep hygiene.