What is 'Normal' Sleep?
How many hours you should sleep each night, and what sleep cycles look like
In my work as a sleep coach for adults with insomnia, I find that many new clients have a number of fundamental misunderstandings about sleep. A few examples include the idea that we all need eight hours of sleep for optimal health (a range as large as five to 10 hours may be appropriate for adults) and that if we don’t sleep through the night we miss out on all the benefits of the deepest stages of sleep.
In healthy sleepers, such misunderstandings are not a big problem. However, if you are struggling with sleep, they can be — because inaccurate sleep thoughts can increase sleep-related anxiety, worry, and frustration, and these feelings can activate the arousal system and make sleep more difficult.
Sleep education is actually a key component of cognitive behavioral therapy for insomnia because it helps address (and correct) dysfunctional sleep thoughts that can increase anxiety and make sleep more difficult.
Having a better understanding of normal sleep can also help you improve your sleep because you will no longer feel the need to hold yourself to impossible standards that aren’t accurate and aren’t helpful.
How does sleep work?
There are two distinct states of sleep. These are rapid-eye-movement sleep (REM sleep) and non-rapid-eye-movement sleep (NREM sleep). Generally speaking, the average adult will spend around 75 percent of their sleep duration in NREM sleep and around 25 percent of their sleep duration in REM sleep.
Sleep usually begins after a period of quiet wakefulness that can last up to half an hour. When we first fall asleep, we typically enter NREM sleep followed by REM sleep.
NREM sleep has three distinct stages that occur in the following order:
Stage one (N1)
This is the very lightest form of sleep and accounts for roughly five percent of total sleep time. It is very easy to be awoken when in this sleep stage. In fact, if you do wake up during N1 sleep you might not even think you have been asleep.
Hypnic jerks tend to be recorded just before we fall asleep (during quiet wakefulness), and when we are in N1 sleep.
Stage two (N2)
N1 sleep helps prepare us for N2 sleep, which is deeper than N1 sleep. This stage of sleep accounts for roughly half of total sleep time. If you wake during N2 sleep, you are far more likely to report that you were asleep compared to when you were in N1 sleep.
Stage three (N3)
After N2 sleep, we progress into N3 sleep, which accounts for roughly one-fifth of total sleep duration (although this is usually less for older adults). This is the deepest stage of sleep in the sense that it’s quite hard to wake someone from N3 sleep. After a period of sleep deprivation, we tend to get more N3 sleep when we are able to sleep.
After going through N1, N2, and N3 sleep, we reverse back through these stages and then enter REM sleep.
The analysis of brainwaves during REM sleep suggests that this stage of sleep is actually quite similar to quiet wakefulness. That’s because, during REM sleep, our brains are far more active compared to any of the NREM sleep stages. Most dreams occur during REM sleep — and it’s during this sleep period that we are most likely to experience sleep paralysis if we are suddenly awoken.
After REM sleep, we will repeat the cycle starting with NREM sleep (although we won’t necessarily follow all the NREM sleep stages in the exact same order). As the night goes on, the amount of time we spend in the deeper stages of sleep (particularly N3 sleep) gets shorter, while the amount of time we spend in REM sleep gets progressively longer.
What it all means
Here are some key points I want you to take away from this knowledge:
We go through a number of different stages of sleep and we cycle through these stages throughout the night.
You may be getting more sleep than you think you are, because when you wake from light sleep you might not even realize that you were asleep.
Most deep sleep occurs earlier in the night. So, if you manage to get a few hours of sleep, you are likely getting the majority (if not all) of your deep sleep.
When deprived of sleep, the body will tend to prioritize deep sleep. REM sleep may also occur earlier in the night (and for longer periods of time).
Since the second half of the night will typically consist of more REM sleep and less of the deeper stages of sleep, waking becomes more common — and this is completely normal!
Periods of REM sleep become longer towards the end of the sleep period, making it more likely that a dream (or a nightmare) will wake you up.
Now you know more about sleep, it may be time to get your friends to learn more about what it’s like to live with insomnia so they won’t spread unhelpful and inaccurate advice!