There are four stages in the sleep cycle and the average person will go through between four and six cycles per night. While it can be incredibly easy to fixate on how many hours you may get and start doing the mental math calculating how much you’ll get if you fall asleep that very second, it is also important to keep in mind whether that sleep will be restful and restorative. With each sleep stage working to help the body recuperate at the end of the day and supporting multiple bodily functions, it is important to understand these different stages to help facilitate more useful sleep each night.
N1
The first stage of the sleep cycle is known as N1, or non-rapid eye movement one. This stage of the sleep cycle is the shortest one out of them all lasting only one to seven minutes on average. In this stage, body and brain activity begins to slow down in small increments. It is very easy to wake someone when they are in this stage, but if they are not disturbed then they can easily transition from this first stage to the second stage of sleep.
N2
Throughout your entire time sleeping, you will likely spend most of your time in the N2 stage. In this stage, the body’s core temperature will drop which is conducive to melatonin production. The muscles will also relax in this stage and both your breathing and your heart rate will slow down. While brain activity does slow down during N2, there are some spikes in activity that act as a safeguard against being woken up. During the first sleep cycle, your body will likely stay in N2 between 10 and 25 minutes. However, with each subsequent sleep cycle, the N2 stage becomes longer. Overall, you can expect to spend about half of your time asleep to be in the N2 stage.
N3/Deep Sleep/Slow Wave Sleep
The third stage of sleep goes by many names as this stage which, in part, comes from the distinctive brain activity that occurs known as delta waves. In this stage, the pulse, breathing, and muscle tone decreases and the body relaxes even more than in the previous stages. This stage is believed by experts to be the most crucial to achieving restorative sleep where the body can both recover from the day and grow further. This stage is also believed to help build immunity and help foster creativity, insight, and improve memory. In the first few sleep cycles, this stage can last anywhere between 20 and 40 minutes, but it works in the opposite way as N2 and will decrease in duration as you continue to sleep. As this stage shortens throughout the night, the time leftover is spent in REM sleep.
REM Sleep
The fourth and final stage of the sleep cycle is REM sleep. During REM sleep, the activity levels in the brain increase dramatically nearly to the same levels as when the body is awake. Despite this peak in neurological activity, the muscles in the body are paralyzed with the exception of the eyes moving rapidly and the muscles that control breathing. This stage of sleep is imperative to function such as memory, learning, and creativity even more so than N3.
Dreams are also most vivid and prevalent during this stage. While dreams do occur in the non-REM sleep stages, they are less common and less detailed. On average, you do not enter REM sleep until you have been asleep for 90 minutes. During your first sleep cycle, REM sleep can last as little as a few minutes, but as you continue through the various sleep cycles it can last as long as an hour. Over the course of your entire night’s sleep, you can expect to spend about a quarter of your time asleep in REM sleep.
What Affects The Sleep Cycle?
There are a number of things that can affect the sleep cycle and how much time you spend in each stage. Age is one factor that plays a role in how much time you spend in each stage. Newborns, for instance, spend most of their time in REM sleep. As they grow, their sleep patterns are more in line with that of adults. Conversely, older adults spend less time in REM sleep on average. Sleep disorders can also affect your sleep cycle with conditions such as sleep apnea and restless leg syndrome (RLS) contributing to waking up in the middle of the night. These awakenings, especially if they’re frequent, can disrupt your sleep cycle causing you to start over from the first stage and ultimately spend less time than necessary in each stage to be conducive to restorative sleep. Additionally, alcohol consumption can affect your sleep cycle in a similar manner. Alcohol can disrupt your REM sleep cycles. While it is in your system, your REM stages are decreased. As it wears off, however, a rebound effect occurs in which your body spends more time in REM sleep.
Key Takeaways
While you cannot wholly control your sleep cycle and how much time you spend in each stage of it, gaining a better understanding of how it operates and what your body goes through in each stage can help you maintain better sleep hygiene. For instance, if you wish to maintain a consistent REM cycle, then avoid alcohol in the time leading up to going to bed. In another example, if you are debating on the duration of your nap, it could be wise to consider the sleep cycle. If you have half an hour free to nap, then it could be wise to set an alarm for only 20 minutes as opposed to a full 30 minutes to prevent yourself from being woken up in the middle of N3 or deep sleep. Being woken up in the middle of a sleep stage can often leave you feeling more groggy than refreshed upon waking up. While your sleep cycle can be somewhat unpredictable, gaining a better understanding of your body’s process brings you one step closer to working with your body, not against it.
