When we sleep, our body cycles through different sleep stages. A good night’s sleep consists of five main stages of sleep, but what does that mean exactly? Why do some sources report five stages and others only four? What differentiates the individual stages of sleep, and why is each one important? When do you dream? Are you cycling through all of the correct stages while you sleep? If you have ever wondered about these questions or been curious about your brain’s behavior when you sleep, then you have come to the right place. Join us while we explore the answers to these questions and more.
This in-depth analysis of each stage of sleep will help you examine and evaluate your sleep patterns. See how they measure up to a healthy sleep schedule. This knowledge will also help you to alter your sleep habits as needed. You will wake up rested and ready for peak performance throughout the entire day.
An Overview of Sleep Cycles
Before we get technical, let’s cover the basics. What is a sleep cycle? When someone discusses sleep cycles, they are referring to your body’s natural progression through the various stages of sleep, from non-REM sleep to REM sleep. What your brain and body focus on during each particular phase define these stages, but more on that later.
How long are sleep cycles? The answer depends on a few variables, including age, genetics, and environmental factors. But for the average person, a sleep cycle lasts approximately 90 minutes to 120 minutes. Your sleep cycle repeats itself, from stage 2-5, until you wake up in the morning. Do you know the number of sleep cycles you experience in a night? How long does a sleep cycle last? Given the time it takes to cycle through the stages of sleep, you will ideally experience 4-5 complete sleep cycles each night. Also, the first sleep cycle you progress through is generally a bit shorter. It is only about 90 minutes in length, with the other periods lasting to about 100-120 minutes.
2 Main Types of Sleep
The two main types of sleep are called REM sleep and non-REM sleep. REM is an acronym for rapid eye movement. While you are in REM sleep, your eyes move back and forth rapidly. Your sleep is considered to be more active. During non-REM sleep, also known as NREM sleep, this eye movement does not occur. Your sleep is considered to be quieter. NREM sleep encompasses three of the five total sleep phases.
Are There 4 or 5 Stages in Your Sleep Cycle?
How many stages of sleep are there? Interestingly, there is conflicting information on the categorization of the different sleep stages. The most recent research and information indicate that there are currently five recognized stages of sleep. However, stages three and four are put together because they both refer to subcategories of deep sleep. Stage three is the gradual start of deep sleep caused by your brain’s production of slower delta brain waves. Stage four is when your brain waves amplify, and you fully achieve deep sleep.
What Are the 5 Stages of Sleep, and How Can You Tell Them Apart?
Now that we have a basic knowledge of what sleep cycles and sleep stages are, let’s dig a bit deeper and get a more detailed understanding. What are the stages of sleep, specifically? Also, how much do the individual phases encompass? Is it a couple of minutes, an hour of sleep, or maybe a little more?
Sleep Stage #1
This is the first of the non-REM sleep cycle stages. It only lasts for a brief period, usually not exceeding seven minutes. During this early phase of sleep, you begin transitioning from being awake to being asleep. When you enter this phase, your brain and body react to the first phase of sleep by slowing down your breathing, eye movements, and heart rate. Your muscles also start relaxing. But occasionally, your muscle may twitch, which could have even woken you up before.
This is the lightest phase of sleep, and you are awakened easily during this part of your sleep cycle. Your brain waves also begin slowing down and producing alpha and theta waves during this phase. When you take a “cat nap,” you are referring to a brief rest in this sleep stage.
Sleep Stage #2
You spend about 40-60% of your total time asleep in the second non-REM sleep stage. During this phase, you continue to relax, and your internal body temperature begins to decrease. Your eye muscle also relaxes, movement stops, and your brain waves continue to slow down. However, your brain activity now produces sleep spindles, which are sudden frequency spikes in brain waves. These brain waves are called sleep spindles because of how they look on an electroencephalogram (EEG). Sleep spindles are believed to aid in memory consolidation.
This phase of sleep is still fairly light even though you spend more of your total sleep time in this stage than any other. When taking a “power nap,” you will want to wake up after this sleep phase before you enter deeper sleep, which is harder to wake up from.
Sleep Stage #3
Stage three is the beginning of deep sleep signified by your brain’s production of slower delta waves, and the complete absence of muscle or eye motion. During stage three, it becomes more difficult to wake up, and you are less responsive to outside stimuli. As we mentioned above, stage three and stage four are grouped together due to their subtle differences, which were undetected for many years.
Sleep Stage #4
Stage four is the main component of deep sleep. The brain’s production of even slower delta waves and the complete relaxation of your entire body signifies this. As an adult, you spend 13-23% of your total sleep time in a deep sleep. This number is greater in children and adolescents as their bodies and brains continue to grow and develop. Your first deep sleep of the night is the longest and can last around 45-60 minutes. After that, the duration of stages three and four will become shorter, and your deep sleep will be lesser as the night progresses. This is the most restorative phase of sleep, making it necessary for normal functioning throughout the day.
Stage five is called REM sleep, or rapid eye movement sleep, and it comprises approximately 25% of your total sleep period. Opposite of deep sleep, the first period of REM sleep that you experience is short, but the period you spend in REM sleep increases throughout the night. During this stage, your heartbeat, blood pressure, and brain activity increase to almost waking levels making this a more active phase of sleep. Breathing during sleep also speeds up on stage five and may even become irregular.
This stage is also restorative and essential for healthy bodily functioning. Another noticeable difference experienced during phase five involves temporary sleep paralysis that restricts muscle motion of your limbs for a brief period while you dream. This paralysis functions as a way to prevent you from acting out your dreams in real life.
What Is Deep Sleep?
What is the deepest stage of sleep? You guessed it. It’s stages three and four of non-REM sleep. During deep sleep, your brain waves slow down and have a large amplitude. This type of brain waves are called delta waves.
Is Deep Sleep Important?
Deep sleep is aptly named because this is the most difficult stage of sleep to wake someone from, especially if they are already sleep-deprived from the previous night or nights. This detachment from external stimuli helps your body and brain perform the restorative and regenerative processes that you need to effectively recover from the previous day’s activities while simultaneously storing energy for the following day’s activities. Your brain also releases the human growth hormone during deep sleep to promote the regeneration and active recovery of your muscle, joints, brain functioning levels, immune system, and of your body overall.
Deep sleep is an integral and necessary part of your sleep cycle if you want to wake up rested and refreshed the next day. If you do not get enough deep sleep, you will most likely feel tired and even irritable in the morning. If you suffer from a deep sleep deficit for an extended period, it can lead to overall health problems affecting your entire body and mental health.
While you are experiencing deep sleep, it is very hard to be woken up. External stimuli often go unnoticed, even if you tend to wake easily during other sleep stages. Not so surprisingly, this is also the stage of sleep where people experience sleepwalking, which is known to be difficult to wake up from.
If you like to nap during the day, whether or not you allow yourself to reach deep sleep during your nap can affect how easily you will be falling asleep that night. If you reach deep sleep during a nap, then it is likely, you will not feel sleepy at the usual time that evening. Unless you are trying to stay up unusually late for something, we recommend keeping your naps short, so you don’t interrupt your normal sleep pattern.
Is REM Sleep Important?
Is REM sleep good or important? Absolutely! As the second most restorative sleep phase, REM sleep stages should not be overlooked or skipped when at all possible. During REM sleep, your body focuses on improving learning capabilities and overall memory consolidation. REM sleep provides your brain with the dedicated time it needs to review, build up, and process all of the information it absorbed during the previous day. Once completed, your brain sorts the information and stores it in your long-term memory accordingly.
How long are REM cycles, generally? The answer to this question varies depending on how many hours you have been asleep. Your first REM sleep cycle usually occurs approximately 90 minutes after you fall asleep and lasts for about 10 minutes. Each subsequent REM cycle increases in length of duration, and your final REM cycle can last as long as one hour.
When Do We Dream?
During what stage of sleep do you dream? As we noted above, the majority of your dreams occur while you are in the REM sleep stage. During REM sleep, your brain is active enough to participate in dreaming while it sorts through the previously absorbed information. Dreams are also believed to be one way your brain enhances its process of sorting through the information it receives during the day. Many people initially dream of simple daily activities and occurrences from earlier in the day, even if they can not remember them when they wake up in the morning. Dreams may also be a function of your body to process emotions, and any stress you may currently be feeling.
While you don’t experience all your dreams during REM sleep, they are often the most vivid. Many people experience their most memorable dreams when they are awoken in the morning and attempt to fall back asleep. However, dreaming is different for everyone, and we are still unsure of the exact purpose of dreams in the first place.
Sleep Patterns Change with Age
Healthy sleep patterns change with age, as do the length of time spent in each of the different sleep cycles. You probably already know that babies, children, and even teens sleep more than a typical adult. You may have also heard that older people tend to sleep fewer hours per night, but how does this interact with your stages of sleep?
The percentage of time spent in each phase of sleep varies with age. When you are young, you spend significantly more time in sleep stages three and four, or deep sleep. Babies spend the most time in a deep sleep. As you grow and your brain develops, it is essential to get a significant amount of deep sleep to facilitate proper development and healthy functioning.
Babies also spend the most amount of time in REM sleep compared to other age groups. Most babies spend as much as 50% of their total hours of sleep time in REM. This REM percentage decreases with age until it reaches only about 20-25% of the total sleep time in adults, and even less in the elderly.
If you think about it, it makes perfect sense. As a baby, everything in the world is new, and you are processing a huge amount of information daily, so more REM sleep is needed. You are also growing rapidly as a child, so you need more deep sleep to enable growth and development at a healthy level. Adversely, when we don’t experience as much growth when we get older, we need less deep sleep. The result of significantly less REM sleep in older individuals results in more forgetfulness, a common trait found in the elderly.
So, how many sleep cycles do we need? The answer depends on your age and what stage of development you are currently experiencing. More sleep cycles for small children and adolescents, and fewer and fewer sleep cycles as we age.
How Does Your Circadian Rhythm Fit into All This?
Your circadian rhythm is an internal biological mechanism that is closely tied to sleep stages. Its way of doing this is by regulating when you are awake and when you are asleep. In turn, your biological clock adjusts to it. Similarly, your circadian rhythm is both controlled and affected by the release of hormones in your body. The temperature of your environment, your internal body temperature, and your metabolism also affect this rhythm.
Consider Tracking Your Sleep Cycle at Home
There are many new products on the market today that allow you to monitor your sleep cycles like those recognized by the National Sleep Foundation or NSF. Try using a wearable item, like a headband, watch, or bracelet to help you track your stages of sleep so you can find out if you lack in any areas. These new monitoring tools track your heart rate, respiration, and blood pressure to analyze your sleep patterns and determine how much time you spend in each of the different sleep levels. Keeping a sleep journal in conjunction with the data your preferred device collects, could help you determine if you need to make changes in your sleep routine to improve your overall mental and physical functionality.
Balance Your Sleep Stages and Improve Sleep Quality Overall
What if you track your sleep, and you find out your sleep stages are imbalanced? Don’t worry, you are one of many people who discover the same, and there are several easy things you can do to efficiently balance and improve the quality of sleep you get each night.
1. Get the Amount of Sleep Your Body Needs
For most adults, the proper amount of sleep is around eight hours. However, this varies from person to person, and only you know how much sleep your body needs to feel well-rested. Children need more sleep than adults, and often they can sleep for up to 14 hours a day, mainly if you include daily naps.
2. Keep Your Bedroom Cool and Dark
You sleep better when you’re body temperature is not overheating and when you are not disturbed by light of any kind. Sorry, but this includes the light emitted from electronics too. Power everything down and draw the curtains.
3. Don’t Eat or Exercise Right Before Bed
Eating a big meal before bed diverts your body’s energy to digestion instead of allowing it to focus on restorative sleep. Exercise right before bed will likely make it harder to fall asleep when you lie down. Exercise usually awakens the muscle you trained and gives you an energy boost, so try to work out at least a couple of hours before you plan on going to bed.
4. Make a Sleep Routine That You Follow Every Night
Do a sequence of activities before bed to alert your body that it is almost time to go to sleep. This could include relaxing muscle stretches, a bath, or even simple activities like combing your hair, brushing your teeth and washing your face.
Also, go to bed and wake up at around the same time each night, even on the weekends. This will lead to a more balanced sleep schedule that leaves you feeling more refreshed and awake in the morning.
Each one of the different sleep stages is important for various reasons. The first stage of sleep is particularly important even though you only fall asleep for a brief period of a few minutes. Without the first sleep stage, you would never truly fall asleep or reach the following four stages. Experiencing issues during the first stage results in sleep disorders like insomnia. Then the second stage of sleep helps your body transition from one step to the next and encompasses the most time overall. Next, the third and fourth stages, also known as deep sleep, work to restore and regenerate brain, muscle, and skin tissue. Lastly, the fifth stage of sleep processes information and stores memories for later recall.
All five stages of sleep are a vital part of your overall sleep health and general health, as well. If you miss some sleep or it is frequently interrupted, then it is not uncommon to feel tired or irritable the following day. So do your best to get the rest you need on a consistent and regular basis. You will thank yourself in the long run.