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While most people are at least vaguely familiar with the concept of REM sleep, there’s actually four different stages of sleep that the body cycles through over the course of the night. The first three are non-rapid eye movement sleep (NREM sleep or non-REM sleep), which is known as quiet sleep and the fourth is rapid eye movement (REM sleep), which is a more active type of sleep.
Below, we’re answering frequently asked questions around dreaming, including when it happens, why it happens, and how it impacts sleep quality.
Dreaming takes place during the fourth stage when we’re in REM sleep. This is when brain waves become far more active, although muscles remain fully relaxed—which is a good thing because it prevents us from acting out our dreams. Because of the disparity between brain activity and inactive muscles (known as atonia), REM is sometimes referred to as “paradoxical sleep.”
Deep sleep takes place during stage 3, during which time it’s difficult to wake up. This is when you get what’s called “delta sleep” or “slow wave sleep” (SWS). The brain is releasing low-frequency, high-amplitude delta waves that cause heart rates and respiration to slow down. The benefit here is for the functioning and restoration of your immune system while the benefit of REM sleep is for cognitive functions such as memory consolidation, creativity, and learning. (1-2)
READ MORE: The Proper Guide To Circadian Rhythms: What it is, how it works, why it's important
Generally, sleepwalking occurs during deep sleep (N3) while vivid dreams take place during the REM stage.
There may be instances of movement in REM stage if one suffers from REM behavior disorder, which is far less common than non-REM sleepwalking.
Although the initial REM sleep phase lasts only about 10 minutes, the periods of REM sleep that follow as you progress through the night become longer and longer—this is why it’s important to prioritize a full night’s sleep, otherwise you’ll be cutting your share of REM sleep short.
In total, we spend about 20 - 25% of our time in this stage, which equates to roughly 90 minutes over the course of 7-8 hours of sleep.
READ MORE: 6 Ways Sleep Deprivation Affects Work Performance
Come adulthood, the amount of time spent in stage 3 (deep sleep, otherwise known as slow wave sleep) decreases while the proportion of sleep in stage 1 and 2 increases. The effect of age on REM sleep, however, is minimal, with sleep research studies finding a 0.6% decrease per decade from age 19 to 75, followed by smaller increases from age 75 to 85. (3)
READ MORE: How Much Sleep Do You Really Need?
- Know your caffeine cutoff
The half-life of caffeine is 5-6 hours (or longer depending on how fast you metabolize it). Sensitivities vary, but because it’s a stimulant, it may cause difficulties in the onset of sleep if it’s still in the body’s system come bedtime.
One study examining the effects of 400 mg of caffeine 30 minutes before bedtime found that it reduced sleep efficiency 5%, prolonged sleep latency (the amount of time it takes to fall asleep) by 12-16 minutes, and reduced total sleep time by 25 - 30 minutes compared to the placebo group.
As a rule of thumb, we recommend limiting caffeine intake to before 2pm; however, if you are sensitive to the effects of caffeine and/or typically go to bed around 10pm, you wouldn’t want to consume it after 12-1pm in the afternoon (which we acknowledge can be difficult for those craving an afternoon pick-me-up to combat sleepiness).
- Avoid alcohol before bed
Although alcohol can be relaxing, it may have adverse sleep effects if consumed too close to bedtime (within 3-4 hours), including fragmented and non-refreshing sleep, increased snoring, delayed onset of REM sleep, and more frequent bathroom awakenings.
READ MORE: The 15 Best + Worst Foods For Your Sleep
- Get on a consistent sleep cycle
Try your best to go to bed and get up around the same time every day—even on weekends—because the physiological part of our bodies thrive off routine and the consistency of the 24-hour day. If the schedule of when we are awake and asleep varies considerably, it can cause confusion for the body and throw off these processes, resulting in feelings of perpetual jet lag that make it difficult to get a good night's sleep.
- Cultivate an evening routine
We hear a whole lot about morning routines that help facilitate a more productive day—whether it be exercising, drinking a full glass of water, meditating, or having a healthy breakfast. But in order to set yourself up for a good start to the day, you have to invest in the end of the day, too. Here’s a list of science-backed activities to incorporate into your evening routine.
- Avoid laying there, “trying” to sleep
If you’re in bed and not sleeping after 20-30 minutes (and not feeling sleepy), then engage in a more restful activity such as reading a non-stimulating book under dim lighting or going to a different room to perform the 4-7-8 breathing exercise. Getting out of bed to perform the relaxing activity is ideal, but if this is challenging or impossible, give it a go in bed.
- Pay attention to temperature
During certain sleep stages, our bodies do not thermoregulate as much, so if the bedroom is too hot or cold, it can lead to sleep disruptions. Right around bedtime, your body temperature drops 1-2 degrees, which signals to your internal clock that it’s time to hit the hay. We recommend keeping your bedroom at a cool 60 - 67°F.
Tired even though it feels like you slept well? There are many potential reasons for this such as sleep apnea, chronic fatigue syndrome, vitamin/mineral deficiencies, narcolepsy, mental health conditions, etc. Another possible culprit is getting too much non-REM, light sleep.
For more sleep hygiene tips, refer to our guide on 16 science-backed things to try if you can't sleep.
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