Sleep is sleep is sleep, right? Not exactly. There are different stages of sleep that the human body cycles through over the course of the night. The duration and purpose of each stage differs, as does the “type.” On the one hand, you have non-rapid eye movement sleep (NREM sleep or non-REM sleep), which is known as quiet sleep. And on the other hand, rapid eye movement (REM sleep), which is more active.

If you’re thinking...wait, I thought there were FIVE stages of sleep... you’d be right. At one time, there were. However, scientists at the American Academy of Sleep Medicine (AASM) recently updated their understanding, combining stages three and four so there are now three NREM stages and one REM stage.

Continue reading for a breakdown of each of the four stages and why they’re important.

Stage 1 (N1)

~5-10 minutes

During the N1 phase, which stands for NREM Stage 1, your brain activity is beginning to slow down. Although muscle twitches can occur, for the most part muscles are relaxing as your brain releases theta and alpha waves. Think of this as the “portal” into sleep. It’s the lightest phase, which is why if you awaken out of it, it won’t be too jarring. You may not even feel like you were sleeping.

Certain people may experience what’s called “myoclonic jerks” during this time, which is when you feel suddenly startled (almost like you were about to fall) for no reason. Sound familiar? It’s far more common than you think.

Stage 2 (N2)

~10-25 minutes

During NREM Stage 2, your core body temperature drops and muscles are fully relaxed. It’s a deeper sleep state than N1, but you can still be awoken during this time without heavy stimulation. This stage is particularly important for the consolidation of memories and, after passing through it multiple times (more on that below), accounts for about 50% of your entire night. (1)

Stage 3 (N3)

~20-40 minutes

N3 is for deep sleep, during which time it’s difficult to wake up. This is when you get what’s called “delta sleep” or “short-wave sleep” (SWS). The brain is releasing low-frequency, high-amplitude delta waves that cause heart rates and respiration to slow down. N3 works wonders for the functioning and restoration of your immune system.

N3 is when sleepwalking tends to happen. (2)

Stage 4 (REM)

~10 minutes (for the first cycle, although it can progress up to 90 minutes later on)

During REM (or rapid eye movement) sleep, brain waves are far more active, although muscles remain fully relaxed—which is a good thing! This is the prime time for dreams to occur, and we don’t want to be acting those out. Because of the disparity between the brain increasing activity and the muscles remaining inactive (known as atonia), REM is sometimes referred to as “paradoxical sleep.”

This stage, which we spend about 20-25% of our time in, benefits cognitive functions (i.e. memory consolidation, creativity, and learning). (3-4)

How we cycle through the sleep stages

The body doesn’t go straight from N1 to REM sleep and back again. Instead, it progresses from N1 through to N3, then back to N2, into REM, and back to N2 again. This cycle repeats four to five times throughout the night, looking something like this:

N1 → N2 → N3 → N2 → REM (multiplied by four or five)

Factors affecting the sleep stages

  • Sleep deprivation
    Unlike insomnia, which occurs when you have difficulty sleeping despite an adequate opportunity to do so, sleep deprivation refers to the lack of an opportunity to satisfy the physiological need to sleep. (5) External restrictions to sleep that cause deprivation can include everything from staying up all night to finish an assignment to working overnight as a nurse. Deprivation occurs when you get fewer than eight hours of sleep a night over an extended period of time, thus disrupting sleep patterns and stages.

  • Sleep disorders
    Sleep disorders such as sleep apnea may cause frequent awakenings throughout the night, which can disrupt your sleep stage and overall sleep cycle.

  • Medications
    Many medications may influence the architecture of your sleep (6) by:

    Causing insomnia:
    Drugs for heart problems and blood pressure, as well as antidepressants, thyroid medications, and decongestants

    Disrupting your sleep quality:
    Drugs for high blood pressure and cholesterol, as well as cough medications (which suppress REM sleep)

  • Alcohol
    Contrary to popular belief, alcohol doesn’t help you get better quality (or longer) sleep. It actually decreases REM sleep for the first two cycles or so, creating an imbalance between slow-wave sleep and REM sleep. Later on, as the alcohol wears off, there are prolonged REM stages. (7)

  • Age
    The older we are (post-adolescence), the less deep sleep we get. Newborns, on the other hand, spend about 50% of their time in REM sleep. (8)


READ MORE:
Sleep Problems During Menopause: Causes + Treatment

How Proper supplements impact the stages of sleep

Proper’s formulations are specially designed to respond differently depending on what stage of sleep you are in.

Ingredients such as GABA and valerian, for example, which produce a calming effect to support relaxation and reduce sleeplessness, begin working prior to and during N1. Venetron®, on the other hand, targets multiple stages. It starts working in N1-2 to help improve sleep initiation and continues working throughout the non-REM deep sleep stage three by supporting sleep cycles and increasing delta waves.

READ MORE: Do Natural Sleep Supplements Work? Our Formulation Scientist Weighs In

The Sleep + Restore formulation contains melatonin, which also impacts multiple stages of sleep. It begins working soon after consumption to help you fall asleep faster (N1) and stay asleep with high-quality, restorative rest (N3 - REM).

For more on the science behind a good night's sleep, read up on the importance of your circadian rhythm and how to regulate it.