Stages of Sleep, Explained
Sleep is paramount to our overall health, but sleep quality can often be overlooked.
Getting a good night's sleep starts with understanding sleep, and familiarizing yourself with your own sleep patterns. The sleep-wake cycle is linked to circadian rhythms, and being mindful of your sleep schedule makes it easier to improve your sleep health.
Additionally, if you have consistent pain or discomfort at night or when you wake in the morning, your mattress and pillow may be partially to blame. Upgrading to a new bed often helps improve how you sleep, which directly affects other aspects of your health.
Deep sleep is commonly linked to stronger cognitive function, better long-term memory consolidation, fewer health problems, improved problem-solving logic, and enhanced innovative thinking abilities.
Some older studies outlined that there were five stages of sleep, but recent research from the National Sleep Foundation has redefined how each stage looks, and ultimately determined that humans rotate through the same four stages of sleep every night.
The stages consist of three different phases of non-REM sleep, and one phase of REM sleep:
- Stage 1 - nrem sleep
- Stage 2 - nrem sleep
- Stage 3 - nrem sleep
- Stage 4 - REM sleep
We’ve outlined those different stages here, so that you can learn more about how your sleep cycle changes at night and with age, and the rationale for why deeper sleep is so important for our overall health.
Stage 1 - N1 sleep
The first stage of sleep is the time in which you’re dozing off, and it only lasts for a short period of time. This period is a non-rapid eye movement stage of light sleep and you may awaken easily or encounter disruptions, but when allowed to relax, Stage 1 is when your body is beginning to shut down.
In Stage 1, you’re certain to experience changes in brain activity. Their heartbeat slows, and their breathing may change, but you’ll still experience brief periods of movement, such as twitches. When left to relax, the individual will be naturally inclined to transition calmly into Stage 2.
Stage 2 - N2 sleep
When you transition from Stage 1 into Stage 2, your body enters a more restful sleep. You may experience increased relaxation in addition to continuously slowed breathing and a further reduced heart rate.
Stage 2 is also a non-REM part of the nighttime routine, and as such, eye movement will stop. The body experiences short bursts of brain activity and can be woken, but if left uninterrupted, will continue to progress towards deep sleep.
During Stage 2, sleep can last for 10 to 25 minutes, but because night sleep is cyclical, you’ll likely experience longer stages of N2 sleep during the night. Collectively, studies show that a person typically spends about half their sleep time in N2 sleep.
Stage 3 - N3 sleep, also known as Slow-Wave Sleep (SWS), Delta Sleep, Deep Sleep
Stages 1 and 2 slide right into Stage 3 non-REM sleep, when your body is even more at rest. It is more difficult to be woken at this time in which your body is most relaxed and focused on restoring itself. Stage 3 is significant when it comes to recovery, growth, immune system responsiveness, and channeling key bodily processes. It’s thought that N3 stages of sleep last for 20 to 40 minutes initially, but subsequent phases in the cycle may get shorter over the course of the night as the body distributes more time to REM sleep.
Stage 4 - REM sleep (Paradoxical sleep)
Though restorative in many ways like Stage 3, REM sleep is much different than all of the non-REM sleep phases. REM stage of sleep is characterized by higher levels of brain activity which results most notably in eye movement (hence, Rapid Eye Movement, or REM). Sleep studies have proven just how dramatically different REM sleep brain waves are compared to other non-REM sleep cycles.
When asleep during the REM cycle, the body temperature drops, and the eyes and breathing muscles are the only functions of your body that are not temporarily paralyzed. You don’t need to remember your dreams to have a good REM cycle, but many people do experience many wildly vivid and creative dreams. Paralysis during REM sleep prevents you from acting out your dreams.
REM sleep occurs about an hour and a half (90 minutes) after you initially fall asleep and can travel through stages 1 through 3. If interrupted, it can take longer to get to REM sleep; similarly, if your sleep is interrupted throughout the night, it may be harder to cycle through the stages continuously to have repeated REM cycles every night.
The first REM cycle may last 10 minutes, and get longer throughout the night. It also may occur for longer periods of time in newborns and young children, which is why it’s believed that REM sleep is closely linked to brain development, memory processing, and learning.
How much sleep do you need?
The hours of sleep you need changes dramatically as you age. Also as you age, the types of sleep you get can be affected more easily by many factors such as medications, sleep disorders such as narcolepsy and sleep apnea, work and life habits that may affect circadian rhythms, and general comfort needs.
- Babies — 16 to 18 hours each day
- Toddlers — 12 to 16 hours each day
- School-age children and teens — 9 to 12 hours at night
- Adults — 7 to 9 hours at night
Without enough sleep, your body lacks the time needed to rejuvenate and restore itself to full function. It’s difficult—and some say, close to impossible—to “make up” after sleep deprivation, so a consistent sleep schedule is critical to all humans. Sleep better, and be rewarded with health. Similarly, having the right environment for sleeping is important.
The comfort layers of the mattress and the ambiance in the room are important to consider if you’re having difficulty getting a good night’s sleep. Learn more about sleep health at our Sleep Tips blog.