How much REM sleep do you need and when does it occur?
If you’re interested in how and why we sleep, you may have heard of REM sleep. But what does REM stand for? Rapid eye movement (REM) sleep is the stage of sleep where your most vivid dreams occur. Find out more about why REM is such an important part of a good night’s sleep, and how you can improve your REM sleep.
When does REM sleep occur?
REM sleep first occurs about 60-90 minutes after you fall asleep. This is at the end of your first sleep cycle of the night, one of four to six cycles you go through per night. Sleep can be divided into non-REM (NREM) and REM sleep. Each cycle is made up of four NREM sleep stages, and ends with the REM stage.
Stage 1 non-REM sleep
Your brain slows down as low frequency brain waves increase and you start to nod off.
Stage 2 non-REM sleep
Your heart rate and body temperature fall in this stage. Your brain activity is characterised by spikes in activity called sleep spindles and K-complexes, while overall activity continues to slow down.
Stage 3 and 4 non-REM sleep
Collectively, stages 3 and 4 of NREM sleep are known as slow-wave sleep, after the slow brain waves that characterise these stages. These stages are now commonly referred to as simply stage 3 NREM. This sleep is the deepest sleep, where your breathing, heart rate and brain waves are the slowest of the night.
REM sleep occurs at the end of each sleep cycle. This means you first enter REM sleep after around 90 minutes, but then leave REM sleep again after 1-5 minutes to start the next sleep cycle. A full cycle takes 90 to 120 minutes to complete, and the proportion of each cycle that is spent in REM sleep increases throughout the night. In total, you spend about a quarter of the night in REM sleep, and most of this is in the second half of the night.
What is REM sleep?
REM is one type, or stage, of sleep that you experience each night. Your brain activity, heart rate, body temperature and muscle movements are all different in REM sleep compared to NREM sleep. REM’s key difference from other sleep stages is the loss of all muscle tone (meaning your muscles are completely relaxed) other than in the oculomotor muscles that control your eyes. The quick movements your eyes make in REM sleep, while remaining closed, are what gives the stage its name.
You may be familiar with the slow, steady breathing of a sleeping person, but during REM sleep our breathing patterns change and can be much more irregular. Your heart rate and body temperature also increase in REM sleep, before dropping back down in the following non-REM start of the next sleep cycle. Brain activity picks up in REM sleep too, in contrast to the earlier stages where your brain waves are slower than when you are awake. Your brain waves also become more varied in REM sleep.
Overall, your brain and body in REM sleep are much closer to being awake than in the other sleep stages, which is possibly why you are much easier to wake in this stage. In fact, sleepers sometimes wake spontaneously from REM sleep, maybe even abruptly ending a vivid dream you were having.
How many hours of REM do you need?
There’s no expert consensus on exactly how many hours of REM sleep you need, but we do know that your sleep needs vary with age. When we are younger, we spend more time in REM sleep. Infants spend almost all night in REM sleep, but by the time we are adults, we only need around two hours of REM per night. This means that in normal, healthy sleep, adults spend around 20 to 25% of the night in REM sleep. The amount of REM sleep you need also changes day to day, depending on your body’s needs. For example, after learning, we spend more time in REM sleep.
Getting enough REM sleep is important: it helps you to consolidate new information into memories, concentrate and regulate your mood. Missing out on REM sleep has been found to impair memory formation, although the mechanism isn’t fully understood. Missing out on sleep generally, but also specifically REM sleep, has been found to make us more sensitive to pain. In general, missing out on any stage of sleep can affect your overall wellbeing, including difficulty concentrating, poor memory and cognitive performance, and feeling tired in the day. Long term, not getting enough sleep is associated with a higher risk of health conditions like cardiovascular disease, depression, and diabetes.
How to increase REM sleep
There are a few things you can do to make sure you are getting enough REM sleep, but generally following good sleep hygiene will help improve your overall sleep and your REM sleep along with it.
Follow a sleep schedule
Going to bed at the same time each night and waking up at the same time each morning makes it easier for you to get the sleep you need. A sleep schedule is important for regulating your circadian rhythm (your body’s internal clock). This helps you to feel sleepy at bedtime, and alert and well rested in the morning. Since most REM sleep happens in the second half of the night, cutting your sleep short by going to bed late may mean you get less time for REM sleep.
Avoid blue lights in the evening
Exposure to blue lights from the screens of electronic devices in the evening, such as your phone and TV, can trick your brain into thinking it is time to be wide awake. This is because it inhibits the production of the sleep hormone melatonin, which can make it harder for you to feel sleepy and lead to you missing out on sleep. Turning off your TV and putting away your phone in the evening can help you to feel tired and fall asleep more easily at bedtime.
Cut down on alcohol
Moderate to heavy alcohol consumption can significantly disrupt REM sleep by delaying the start of REM sleep. It can also reduce the amount of time you spend in REM sleep, so avoiding alcohol can help you sleep better and spend a normal amount of time in REM sleep.
Improve your sleep environment
Your sleep environment is an important part of getting enough, good quality sleep with enough time spent in each stage. This means ensuring your room is dark, at the right temperature for sleep (around 18°C), and includes a bed that is comfortable and large enough to spread out on. Most UK adults sleep on a double mattress, but this isn’t usually big enough for two adults to share comfortably. A larger bed can help reduce disturbance from sleeping partners, and help you sleep uninterrupted. The comfort of your bed is vital too: it should be supportive and capable of holding your spine in its ‘neutral’ s-shaped curve. Buying an adjustable mattress can effortlessly support you in this position, minimising soreness from pressure points and helping you to sleep restfully through REM, and the other stages of sleep too.
Speak to your doctor about sleep problems
Some sleep disorders are associated with REM sleep, or disrupt REM sleep more than other stages of sleep. For example, sleep apnoea, which can occur in any sleep stage but often in REM sleep, can affect the amount of REM sleep you get.
Another example is those with REM sleep behaviour disorder (RBD) sometimes don’t lose muscle tone during REM sleep. This means that they can move around while asleep, and may act out their dreams. For example, some people move their limbs in their sleep, which can cause injuries. You should always seek medical advice if you think you might have a sleep disorder, as they can help identify the cause and offer you specific care.
Is deep sleep or REM better?
Deep sleep, or slow-wave sleep, is the final stage of sleep before REM sleep begins. You spend slightly less time in deep sleep than REM sleep: around 13 to 23% of your sleep is deep sleep. So how is deep sleep different from REM sleep?
|Features of REM Sleep||Features of Deep Sleep|
|Loss of muscle tone, other than the eyes||Partial muscle tone|
|Characterised by rapid eye movements||No rapid eye movements|
|Faster brain waves||Slower brain waves|
|More vivid dreams||Fewer dreams, and less vivid|
|Increased heart rate||Slower heart rate|
|Irregular breathing||Slower, regular breathing|
|More easily woken||More difficult to wake up|
While REM sleep is important for forming longer-term memories, memories are also consolidated during deep sleep. Experts think both deep and REM sleep have specific functions that help our minds and bodies function normally in the daytime:
|Functions of REM Sleep||Functions of Deep Sleep|
|Memory consolidation||Memory consolidation|
|Learning and emotional processing||Learning and emotions processing|
|Brain development||Physical repair and growth|
|Wakefulness preparation||Immune system regulation|
|Detoxification of the brain|
Every sleep stage is important, but REM sleep is particularly crucial for memory, dreaming, and emotional processing. Deep sleep is equally important and is particularly vital for physical repair and keeping your immune system functioning well.
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