REM Sleep: What It Is and Why It’s Important

How Rapid Eye Movement (REM) Sleep Plays a Critical Role in Your Overall Health and Well-Being

“To sleep, perchance to dream.”

That’s a famous quote from the play The Tragedy of Hamlet by William Shakespeare. And although he probably didn’t realize it, Shakespeare was referring to a very special stage of sleep: rapid eye movement sleep—better known as REM sleep.

“REM sleep is most often associated with dreaming,” says Robert Miller, the Apria Healthcare Vice President of Sleep Business. “But it also plays an important role in your memory, mood, and mental focus.”

REM sleep was first described in the 1950s. A group of researchers studying infants noticed that their eyes moved rapidly from side to side as they slept. Hence the name.

What Are The 4 Stages of Sleep?

Sleep is divided into 4 stages. The first 3 are known as non-rapid eye movement (non-REM or NREM) sleep, and the fourth is REM sleep.

On an average night, most people go through 4 to 6 cycles of sleep stages. The first is usually the shortest, 70 to 100 minutes, while later cycles last 90 to 120 minutes.

For people with sleep apnea, it’s helpful to understand all four stages to manage their condition more effectively.

What Happens During the 3 Non-REM Stages of Sleep?

Before you reach REM sleep, you go through 3 stages:

N1 is the “dozing off” stage, usually lasting 5-10 minutes. Your breathing is regular, but your body hasn’t completely relaxed and your brain activity begins to slow down. Your eyes are closed, but it’s easy for someone to wake you.

N2 is when you begin to sleep lightly. Your heart rate and brain waves slow, your body temperature drops, your muscles relax, and your eye movement stops. You are getting ready for deep sleep. N2 can last 10-25 minutes

N3 is known as the “deep sleep” stage. Experts think this may be the most restful stage of sleep. It's harder to wake up, and if you did, you’d probably feel disoriented. Your body relaxes, your breathing rate decreases, and your heart rate slows. It’s also the stage that helps strengthen the immune system, build bone and muscle, and even contribute to creativity and memory. N3 commonly lasts 20-40 minutes.

What Happens During the REM Stage of Sleep?

REM sleep happens about 90 minutes after you fall asleep. As previously stated, even though your eyes are closed, they dart around quickly.

Much of your body functions the same way as if you were awake. However, your heart rate and blood pressure increase, your breathing becomes irregular, your brain waves become more active, and you have a temporary loss of muscle tone.

Apria’s Robert Miller adds, “The first REM sleep stage usually lasts about 10 minutes. But as the night wears on, REM stages get longer. The final one can last up to an hour!”

REM sleep isn’t just reserved for humans. Other mammals, reptiles, and most birds experience REM sleep. [However, owls don’t have rapid eye movement simply because they can’t move their eyes. And some birds lose muscle tone in their necks to allow their heads to rest.]

What Are the Main Differences Between REM and Non-REM Sleep?

Here’s a handy “at-a-glance” reference table.

  REM sleep Non-REM sleep
Eye movement Rapid None
Brain wave activity Increases No change
Muscle tone Complete loss Partial loss
Breathing Fast, irregular Slow, steady
Heart rate Increases



If you are having problems sleeping, be sure to speak with your healthcare providers and Apria's sleep coaches (877.265.2425). Robert Miller states, “Working closely with you, they can customize a plan that helps you get the quality and quantity of sleep you’ve always dreamed of.”


About the AuthorApria

Apria is a leading provider of home healthcare equipment and related services across the USA, offering a comprehensive range of products and services for in-home care and delivery of respiratory therapy, obstructive sleep apnea treatment, and negative pressure wound therapy, along with additional equipment and services.