Deep Sleep: Meaning and Stages
You may have heard that adults need between 7 and 9 hours of sleep each night. But, the quality of sleep you get also matters.
What is deep sleep?
While you rest, your body goes through different stages of the sleep cycle. Deep sleep, for example, is the stage of sleep you need to feel refreshed when you wake up in the morning. Unlike rapid eye movement (REM) sleep, deep sleep is when your body and brain waves slow down.
It’s hard to wake from a deep sleep, and if you do, you may feel particularly groggy.
Stages of sleep
NREM Stage 1
The first stage of the sleep cycle is a transition period between wakefulness and sleep.
If you awaken someone during this stage, they might report that they were not asleep.
During stage 1 sleep:
- Your brain slows down
- Your heartbeat, your eye movements, and your breathing slow with it
- Your body relaxes, and your muscles may twitch
This brief period of sleep lasts for around five to 10 minutes. At this time, the brain is still fairly active and producing high amplitude theta waves, which are slow brainwaves occurring mostly in the brain’s frontal lobe.
NREM Stage 2
According to the American Sleep Foundation, people spend approximately 50% of their total sleep time during NREM stage 2, which lasts for about 20 minutes per cycle.
During stage 2 sleep:
- You become less aware of your surroundings
- Your body temperature drops
- Your eye movements stop
- Your breathing and heart rate become more regular
The brain also begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles. They are thought to be a feature of memory consolidation—when your brain gathers, processes, and filters new memories you acquired the previous day.
While this is occurring, your body slows down in preparation for NREM stage 3 sleep and REM sleep—the deep sleep stages when the brain and body repair, restore, and reset for the coming day.
NREM Stage 3
Deep, slow brain waves known as delta waves begin to emerge during NREM stage 3 sleep—a stage that is also referred to as delta sleep. This is a period of deep sleep where any environmental noises or activity may fail to wake the sleeping person.
Getting enough NREM stage 3 sleep allows you to feel refreshed the next day.
During NREM stage 3 sleep:
- Your muscles are completely relaxed
- Your blood pressure drops, and breathing slows
- You progress into your deepest sleep
During this deep sleep stage, your body starts its physical repairs.
Meanwhile, your brain consolidates declarative memories—for example, general knowledge, facts or statistics, personal experiences, and other things you have learned.
Stage 4: REM Sleep
While your brain is aroused with mental activities during REM sleep, the fourth stage of sleep, your voluntary muscles become immobilized.
During REM sleep, your brain’s activity most closely resembles its activity during waking hours. However, your body is temporarily paralyzed—a good thing, as it prevents you from acting out your dreams.
REM sleep begins approximately 90 minutes after falling asleep. At this time:
- Your brain lights up with activity
- Your body is relaxed and immobilized
- Your breathing is faster and more irregular
- Your eyes move rapidly
- You dream
Like stage 3, memory consolidation also happens during REM sleep. However, it is thought that REM sleep is when emotions and emotional memories are processed and stored.
Your brain also uses this time to cement information into memory, making it an important learning stage.
How to get deep sleep at night:
6 tips to sleep better at night
1. Stick to a sleep schedule
Set aside no more than eight hours for sleep. The recommended amount of sleep for a healthy adult is six to eight hours. Go to bed and get up at the same time every day, including at weekends. Being consistent reinforces your body’s sleep-wake cycle.
2. Pay attention to what you eat and drink
Don’t go to bed hungry or stuffed. In particular, avoid heavy or large meals within a couple of hours of bedtime. Discomfort might keep you up.
3. Create a restful environment
Keep your room cool, dark and quiet. Exposure to light in the evenings might make it more challenging to fall asleep. Avoid prolonged use of light-emitting screens just before bedtime.
4. Limit daytime naps
Long daytime naps can interfere with night-time sleep. Limit naps to no more than one hour and avoid napping late in the day.
5. Include physical activity in your daily routine
Regular physical activity can promote better sleep. However, avoid being active too close to bedtime.
6. Manage worries
Try to resolve your worries or concerns before bedtime. Jot down what’s on your mind and then set it aside for tomorrow.
Stress management might help. Start with the basics, such as getting organized, setting priorities and delegating tasks. Meditation also can ease anxiety.