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Every 90-120 minutes while you’re asleep, your brain cycles through 4 different sleep stages. Ideally, you want to spend a significant amount of time in the deeper stages every night, because each stage does something unique for your body and mind.
Let’s take a closer look at the 4 stages of a sleep cycle and why each one is important.
Stage 1 sleep is the shift from wakefulness to sleep and is the lightest form of sleep. It typically only lasts 5-10 minutes, during which your brain activity begins to calm down and you begin to doze off.
During stage 1 sleep, you experience:
You may also experience myoclonic jerks during stage 1 sleep: the startling moments when your body twitches that can feel like you’re falling off a cliff. Myoclonic jerks are an occasional side effect of your brain function changing from an alert state to a resting state, and they happen to almost everyone at some point or another.
Stage 2 begins when you go beyond drowsiness and actually fall asleep. It’s still considered light sleep, but you experience a greater shift in body changes, including:
You’re usually in stage 2 sleep for 10-60 minutes, depending on the sleep cycle you’re in. You move past stage 2 sleep quickly during your first sleep cycle of the night. But as time goes on, your brain no longer needs the restorative benefits of deeper stages, and you begin to spend the majority of your cycles in shallow stage 2 sleep
Despite overall slower brain function, your brain also produces short, rapid bursts of activity during stage 2 sleep. These bursts are called sleep spindles, and researchers believe that they help you break down and store memories from the previous day. People who focus on learning new information during the day see a significant increase in sleep spindles that night.
Sleep spindles may also make you harder to wake up by telling your brain to stop responding to stimuli in the world around you
During stage 3 sleep, you begin to produce delta brain waves: slow, steady waves of electrical activity in your brain. Delta waves are the main sign that your brain is in a state of deep, restorative sleep. For this reason, stage 3 sleep is sometimes called “delta sleep” or “slow-wave sleep.”
Once you enter stage 3 sleep, your muscles relax completely. Your heart rate and breathing become very slow and almost perfectly regular, and you become quite difficult to wake up.
You typically stay in stage 3 sleep for 20-40 minutes, with more time at the beginning of the night and less time the longer you sleep.
Stage 3 sleep activates your glymphatic system, which uses the fluid around your brain and spine to wash away cellular waste that builds up during the day.
Notably, your glymphatic system flushes out beta-amyloid plaques— bundles of proteins that seem to be a main cause of Alzheimer’s Disease—during deep sleep..
During stage 3 sleep, you also begin to repair cellular damage from the previous day. You experience a large increase in human growth hormone (HGH), which restores cells in both your body and brain, stimulates fat loss, and improves muscle power output.
Stage 3 sleep also stimulates creative thought. Studies show that people who get more stage 3 sleep experience increases in creative problem solving and insightful thought
Stage 4 sleep, also called rapid eye movement (REM) sleep, is the deepest stage of sleep. You continue to experience slow, steady delta brainwaves during this stage, but your eyes also begin to dart rapidly back and forth in a random pattern.
Stage 4 sleep usually lasts from 10-60 minutes per sleep cycle, with more time in stage 4 for the first cycles of the night and less time in stage 4 as the night goes on.
Interestingly, you also see a rebound effect with this sleep stage. If you’ve been deprived of deep sleep for previous nights, you enter stage 4 sleep faster and stay there longer until you’ve made up the difference.[15] The rebound effect suggests that stage 4 sleep is particularly important to your physiology— if you miss it, your body has a system in place to make up the difference.
REM sleep is also when you dream, which researchers believe is the result of memory formation. The theory is that when you consolidate memory, your brain processes the various experiences and thoughts you’ve had recently.
The thoughts and experiences are varied, but your brain processes information in narrative (story) form, so it ties the different memories together to form a dream as it processes them.
That explains why your dreams may be related to things you’ve experienced or thought about recently—and why they aren’t bound by the possibilities of the real world.
REM sleep also seems to be particularly important for mood and mental wellbeing. People who don’t get enough REM sleep see an increase in anxiety and depression.
Sleep is a pillar of high performance. It affects almost everything you do: your mood, cognition, focus, physical ability, and more.
If you want to improve your sleep, nootropics are a great place to start.
