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REM Sleep Vs. Deep Sleep

Table of Contents

Even if you’re blissfully unaware of what’s happening, parts of your brain and body are hard at work while you’re asleep. That’s why getting enough sleep is essential. But the amount of time you spend in bed isn’t all that matters — quality is important too. During a single night, the brain cycles through different phases, all producing specific benefits and complementing each other. Understanding and tracking these phases can help you improve your sleep and overall wellbeing. 

The Sleep Cycle

A typical sleep cycle consists of four stages, with each stage falling into one of two categories: REM (rapid eye movement)  and non-REM (NREM). NREM stages can further be divided into light and deep sleep. One full cycle that includes all four stages lasts 90 to 110 minutes, so on average, you should be completing 4 to 6 cycles during a single night. 

When you drift off, you first enter non-REM sleep, which gradually progresses from light to deep over the course of an hour and a half. You then have a brief period of REM sleep that only lasts one to five minutes. But as the night goes on, you’ll experience less deep sleep and more REM, with the most prolonged REM phase just before waking.

What Happens at Each Stage?

During each phase of the sleep cycle, different parts of your body and brain are active as specific processes take place to prepare you for the day ahead. 

Stage 1: The first stage of NREM sleep lasts five to 10 minutes. During this period, your body and brain begin to slow down. Your muscles may occasionally twitch, a phenomenon known as a hypnic jerk. If you wake during this stage, it might feel like you didn’t sleep at all. 

Stage 2: The second stage of NREM accounts for about 50 percent of the total sleep cycle. In this phase, your eyes stop moving, muscles relax, and core body temperature decreases. Brain waves also slow down, with occasional bursts of high-frequency waves known as sleep spindles. Researchers believe these are important for committing new motor skills to memory. 

Stage 3: The third phase of NREM is deep sleep. At this stage, the brain produces very slow waves, known as delta waves. Your eyes turn upward, and it’s very difficult to wake up. Breathing slows to about 15% lower than waking. Your heart rate is also slower during deep sleep vs REM – about 20 to 30% lower than when you’re awake and resting. 

Stage 4: After deep sleep, the REM cycle begins. During REM, your eyes move rapidly from side to side beneath your lids, and your heart rate and breathing speed up. It is challenging to move, and your limbs may become temporarily paralyzed. Some scientists theorize this is to prevent you from acting out your dreams. During REM, brain activity is similar to when you’re awake, which is why most vivid narrative dreams occur during this stage. Because the muscles are so relaxed at this point, sleep apnea may be worse.

Deep Sleep Vs. REM: Which Is More Beneficial?​

Deep sleep and REM sleep both have particular benefits. Without enough of either, your body and mind can’t fully recover and rejuvenate. 

Deep Sleep

Most physical restoration processes occur during deep sleep. 

  • Bone and Muscle: During deep sleep, blood flow and protein production increase, and the pituitary gland secretes growth hormones to help the body repair and build bone and muscle.
  • Immune System: With various bodily processes slowed down during deep sleep, the immune system has more energy to recalibrate, fight infections, and perform essential healing functions. When you are sick, the immune system even alters your sleep cycle, so you spend more time in deep sleep, enabling you to feel better faster. Not getting enough sleep can prolong recovery times and increase your chances of getting sick.
  • Memory & Learning: Deep sleep is essential for learning and long-term memory. Some experts say delta waves transport memories from the hippocampus to permanent storage areas in the brain.

REM Sleep

Most physical restoration processes occur during deep sleep. 

  • Emotions: The amygdala, the part of the brain responsible for regulating emotions like fear and aggression, is most active during REM sleep, and some experts theorize dreams play an important role in emotional processing. Getting enough REM sleep enables us to cope with difficult emotions and prepares us to face challenges appropriately in the day to come.
  • Memory:  Although some cognitive functions occur during deep sleep, most memory consolidation happens during REM, as the brain sorts new information and motor skills and commits certain things to long-term memory. Research also suggests REM sleep improves creativity and problem-solving skills.

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How REM and Deep Sleep Stages Change As You Age

Just like a person’s dietary requirements change with age, the amount of REM sleep vs. deep sleep they need does too. 

  • Children: Babies need more sleep than the rest of us. They also need more REM sleep, specifically. Some scientists think this is because of REM’s role in brain development. As the brain matures, the need for sleep – and REM declines and continues to diminish with age.
  • Teens: People ages 13 to 18 only need about eight to 10 hours, though this can fluctuate. Hormones and puberty-related changes can also cause daytime sleepiness.
  • Adults: Most adults need around seven to nine hours of sleep each night. During this time, the average person completes three to five complete sleep cycles in an evening, with about one to two hours of deep sleep and 90-120 minutes of REM.
  • Seniors: People over 65 usually sleep less – around seven to eight hours, due to disruptions to their circadian rhythms. They also spend slightly less time in deep sleep than their younger counterparts.

How Can I Track My Sleep Cycles?

Because there are benefits to REM and deep sleep, ensuring you get enough of both can help you feel and perform your best each day. 

While scientists use a method called polysomnography to study sleep in the lab, you can sync Welltory with a number of devices to get similarly reliable results about the quality of your sleep.

Wearable devices, like Apple Watch or Fitbit, track your heart rate, as you’ll recall, changes depending on what phase of sleep you’re in.  Alternatively, you can track your sleep with apps like Sleep Cycle and Sleep as Android and see how much time you spend in different sleep stages.

Detailed Sleep Score feature in Welltory

Welltory analyzes the data from these devices and apps to produce personalized insights and recommendations to help you optimize your sleep and make sure you’re getting enough REM and Deep sleep each night.

With Welltory’s sleep analysis, you’ll also get a sleep score that can show you how well you’re meeting your sleep goals every night, using parameters like how well you recovered and whether or not you’re going to bed and waking up at the best time for your needs.

Making sure you’re getting quality sleep will not just help you feel more energized the next day but will also support your body’s many systems so you can live a healthy and productive life.

Welltory Team, 12 Jan. 2023

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