On average, we spend about one-third of our lives sleeping—or trying to. But, when you’re asleep, do you know what actually happens within each stage? Do you know what’s going on in your brain and throughout your body?
Knowing what takes place within the different sleep stages can lead to improvements in your sleep quality and quantity when nighttime rolls around.
Let’s explore everything you need to know about each of the stages of sleep.
What Are the Stages of Sleep?
We understand that getting your recommended hours of sleep each night can be a challenge. However, to have a productive and energized day, sleep is one of the integral steps.
To know what truly happens when you drift off to dreamland, let’s dive into how many stages of sleep there are, and what occurs during each stage.
There are five different stages of sleep:
- Stage One: Sleep Onset
- Stage Two: Slow-Wave Sleep Begins
- Stage Three: Begin to Experience Deep Sleep
- Stage Four: Deepest Sleep
- Stage Five: REM Sleep
Along with the REM stage of sleep, stages one and two are referred to as the lightest stages of sleep. Stages three and four are known as the deepest sleep stages.
Each of these five sleep stages play an important role in helping us to maintain our health and wake up feeling rested and rejuvenated. Each of the individual stages pair together to provide you with the quality rest you deserve.
During a typical night, you will on average cycle through each stage of sleep between four and six times. Each full cycle (from stage one to REM sleep) lasts approximately 90 to 110 minutes.
What Occurs During Stage One Sleep?
Stage one sleep is often referred to as the transitional phase of sleep or sleep onset. It takes place when you first rest your head on your pillow and begin to float in and out of consciousness.
Stage one is the brief, light, and non-REM sleep stage. You will be partially awake at this point as your mind starts drifting off, and you begin to wind down. You may even start to dream.
During stage one sleep, your muscles may jerk and force you back awake. If you’ve ever experienced the falling sensation when drifting off, you’re not alone. That sensation goes by the name of hypnic myoclonia or hypnic jerk.
When your muscles finally relax, your body will start to transition (hence the name transitional phase) from stage one in to stage two.
What Occurs During Stage Two Sleep?
Most people spend about half of their time asleep in stage two sleep. During stage two, the body goes through alternating periods of muscle tension and relaxation. Like stage one, this is also a non-REM lighter sleep stage.
During stage two sleep, your heart rate starts to slow down, and your body temperature begins to decrease. Eye movement and brain waves slow down as well.
In stage two sleep, you will still experience occasional bursts of brain waves. These bursts are known as sleep spindles, which is where memory consolidations occur.
What Occurs During Stage Three Sleep?
When you enter stage three sleep, you begin to experience deep sleep. During this deep sleep stage, your breathing and heartbeat slow down even more. Your body temperature will decrease, and your brain waves reach their lowest levels of activity.
Your muscles will relax during stage three sleep, making it difficult for others to wake you up during this stage.
What Occurs During Stage Four Sleep?
Have you ever wondered, “what is the deepest stage of sleep?” Enter in stage four sleep where deep sleep and healing happens. Once your temperature, heartbeat, and breathing have slowed down, your body can get to work repairing the damage that took place throughout the day.
During stage four, tissue growth and repair occurs. Your body releases important hormones at this time to restore cellular energy, including human growth hormone.
To feel rested the next day, it’s imperative that you spend time in stage four sleep. Without stage four sleep, you may find that you have a hard time recovering from workouts or injuries since your body isn’t producing adequate amounts of growth hormone.
What Occurs During REM Sleep?
Rapid eye movement (REM) sleep is also known as the fifth sleep stage. REM sleep is when you’re most likely to experience vivid dreams.
During REM sleep, your eyes move around rapidly in various directions. In this stage, your breathing is shallow and irregular, and your heart rate and blood pressure levels will rise.
Your limbs and muscles become paralyzed temporarily as well. This is a protective mechanism that keeps you from getting out of bed and acting out your dreams.
REM sleep is important to help revitalize your brain, which allows you to feel sharper and more alert when daytime arrives.
How Sleep Apnea Affects Your Sleep Cycle
Sleep apnea can occur during any of the sleep stages. However, it can often be the worst during REM sleep as a result of the muscle tone in your upper airway naturally becoming reduced.
If you frequently wake up throughout the night as a result of not utilizing your sleep apnea treatment, then you will spend less time in the deep, revitalizing stages of sleep. Less time spent in deep sleep can cause you to wake up feeling less rested and lead to fatigue throughout the day.
Do You Need Help Improving Your Sleep Cycle?
Now that we’ve uncovered what happens when you sleep at night, do you think you’re getting your highest quality of sleep? Do you think you’re spending a sufficient amount of time in each of the five sleep stages?
If your sleep is fragmented due to sleep apnea or if you just struggle with getting high-quality sleep in general, we’re here to help! Try creating a bedtime routine, using a sleep tracker, or limiting your caffeine or sugar intake to catch your best zzz’s and cycle through each sleep stage.