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The Difference Between REM and Deep Sleep

Posted by Emily Bertha
The Difference Between REM and Deep Sleep

All sleep is not the same. You’ve probably heard about light sleep and deep sleep, and many often equate deep sleep with REM sleep. Just as light and deep sleep are different from one another, REM and deep sleep are two completely different sleep stages, each with defining characteristics. There are five different stages of sleep, all which contribute to your body’s circadian rhythm, or natural body clock. REM and deep sleep are stages three and four of sleep.  


Rapid eye movement, or REM sleep, is the deepest sleep stage. The eyes move more rapidly in all directions during REM sleep, as its name indicates. REM is the fourth stage of sleep.

  • Time: REM sleep occurs approximately 90 minutes after you fall asleep.
  • Body: Your heart beats faster, and your heartbeat will likely become irregular during REM. Aside from a change in heartbeat, the body is largely inactive during this phase of sleep.
  • Brain: REM sleep is associated with intense brain activity.  This is the stage where you’ll likely experience active and vivid dreams. Sleepwalking and bedwetting incidents occur only during REM. REM sleep restores your brain and is important for your learning as well as your memory.
  • Length: There are different periods of REM sleep, the first lasting about 10 minutes. There are about three to five periods of REM stages per night.The length of REM stages increase throughout the night, and the final stage can be up to an hour.

  • Deep Sleep

    Deep sleep is non rapid eye movement, or NREM. There are three other NREM stages as well. Other names for this deep sleep stage are slow-wave sleep, delta sleep, and N3 since this is the third stage of sleep.

  • Time: The body enters deep sleep anywhere from a half hour to 45 minutes after falling asleep.
  • Body: Unlike REM, deep sleep is known for the changes in your body rather than your brain. Your breathing slows and your heartbeat is regular during this stage. The muscles in your body become completely relaxed, and you typically sleep through any external sleep distractions such as loud noises. Deep sleep is extremely important to overall health because it’s during this phase that the body naturally heals itself. Your body replaces cells, heals wounds, and builds muscle tissue, all while you’re sound asleep.
  • Brain: There are almost always no dreams during this period of sleep. Although naturally unlikely, if you do wake up during deep sleep, you’ll feel groggy and disoriented at first. It is during light sleep that you wake up the easiest. Smart alarms like the Eight sleep tracker wake you up within a half hour of your alarm so you can always awake feeling refreshed.
  • Length: Deep sleep usually lasts anywhere from 1-2 hours, or 20-25% of your overall sleep. Some people may need more deep sleep than others as every sleeper is different.

  • In order to get your best sleep yet, you’ll need a sleep tracker like Eight’s that analyzes your nightly sleep data and tells you exactly how much sleep you’re getting in each stage. Sleep trackers compare this information to how much time of each sleep stage your body actually needs. By following the simple steps sleep trackers suggest such as avoiding caffeine before bed, you can help regulate your sleep and improve your overall sleep health.