We all have different sleep habits and our sleep requirements vary by individuals and age. Going through sleep cycles requires first falling asleep (feeling drowsy –> falling asleep –> sleep cycles). None of us should go to bed/try to fall asleep until we are drowsy. Falling asleep should feel like sliding into unknown, somewhere where it’s soft, warm and timeless. It’s a place where future, history and past collide. For some people falling asleep has become painful. They fight night after night and ponder how to do it. The skill to ‘let it go’ has been totally lost.
Falling asleep is individual, as is sleep, and for that reason we have the tools to influence on it on our own. At the end of the day, we do have the answers in our own hands. Only in extreme cases do sleep experts advise to use medicine, and only short-term. With sleeping pills we outsource the capability to fall asleep and the trust inside us (to fall asleep naturally) gets broken. A healthy person falls asleep in ~15 minutes.
Sleep cycles and stages
It’s good to realize that sleep is not similar every night. Even good sleepers have bad nights! Our sleep requirements also vary by our life situation and stress tolerance.
Different sleep cycles repeat during the nights. Every cycle lasts around 90-110 minutes. One night contains around 4-5 cycles. We speak about dozing, light sleep and deep sleep. When we go to sleep, we first doze which initiates other sleep stages/phases. We are still aware of what happens around us but the level of brain performance has been lowered. From light sleep (muscles relax and metabolism balances) we fall into deep sleep and then we sleep like a log. Breathing is heavy and heart beat is slow. We renew ourselves during the deep sleep and our energy stores start to fill up.
The timing of these cycles is called circadian timers which influence when you sleep. For example, when you travel across time zones, it is the disruption to this timer that causes a jet lag. Some people are more sensitive to these timers than others. Around half of adult sleep is light sleep. We sleep deep sleep mainly during the first 4-5 hours and its share of the total night is around 25%. During the early hours we start to dream.
Normal sleepers stay awake around 22 minutes every night. Waking up couple of times a night is not abnormal if you fall back asleep in around 10 minutes. Middle aged people get the least sleep. As we get older we tend to sleep less during the night but a bit more around the clock.
Each 90-minute sleep cycle is made up of four stages/phases of non-REM (rapid eye movement) and REM sleep. There’s different ways to call these phases but this might be easiest way to get a picture:
- Sleep stages 1 and 2: Light sleep (warm-up for deep sleep).
- Stage 1: This phase is normally from seconds to few minutes. Sleep is light and superficial and it can be that we often don’t even feel like sleeping.
- Stage 2: This phase can take ~20 minutes. Muscles relax and we see light dreams.
- Sleep stages 3 and 4: Deep sleep (nourishing, peaceful sleep)
- Stage 3: This phase can take ~10 minutes. Heartbeat, blood pressure and body temperature go down.
- Stage 4: This phase is around ~55 minutes. Vital functions further slow and we are in very deep sleep, motionless and can’t remember any dreams.
- Stage 5: REM sleep/ R-Sleep (dreaming)
- This phase is estimated to last around ~15 minutes. With narcolepsy patients REM-sleep starts immediately after falling asleep.
Throughout the night we cycle between non-REM light sleep, deep sleep and REM shallow dreaming sleep and as we progress through the night the stage 4 (deep sleep) become more and more shallow. As a consequence, our deepest deep sleep occurs earlier in the night.
Why do we need different sleep stages?
We believe that deep sleep relates more to metabolism, recovery and rest whereas REM-sleep is more vital for spiritual life, memory, learning and mental balance.
We have different emphases within sleep cycles during the night. We have more deep sleep earlier in the night and more REM sleep in the small hours. This can also be explained in the following way: we need deep sleep to keep our vital functions nourished and re-vitalized so that comes first in the priority order. However, REM-sleep is equally important, only for different reasons.
We need REM sleep to understand and handle everything we have learned and understood during the day. In fact, in REM sleep we go through a very important tidying up and clearing out process: we might dream about our conversations, to-do lists, chores and anything that is occupying our minds to sort out our filing so that the next day we feel mentally sharp and organized.
Our internal 24–hour sleep–wake cycle, otherwise known as your biological clock or circadian rhythm, is regulated by processes in the brain that respond to how long you’ve been awake and the changes between light and dark. At night, your body responds to the loss of daylight by producing melatonin, a hormone that makes you sleepy. During the day, sunlight triggers the brain to inhibit melatonin production so you feel awake and alert.
Sleep requirements by age
Sleep requirement varies from one person to the next and young people tend to need more than the elderly. Some experts also speak about two types of sleep: core sleep versus optional sleep. Core sleep is the first three sleep cycles (the initial 4-5 hours of sleep) necessary for human beings to function normally and properly. Optional sleep is the ‘nice to have’ sleep that we can reasonably do without – another ~4 hours. However, there are also large variations in how much sleep we need according to our stage of growth and aging (see table below). Table below shows typical sleep requirements. Please bear in mind that some people survive with 3-5 hour sleep a night. Genetic differences explain biggest deviations.
In addition to age and already mentioned factors, following factors can also impact the need for sleep:
Pregnancy: Changes in a woman’s body during pregnancy can increase the need for sleep.
Aging: Several recent studies prove that sleep get poorer and shorter as we age so it can also be regarded as natural and unavoidable element of getting older. As we get older, sleeping patterns tend to change. Older adults tend to sleep more lightly and awaken more frequently during the night than do younger adults. This may create a need for or tendency toward daytime napping. Much of the sleep disturbance among the elderly can be attributed to physical and psychiatric illnesses and the medications used to treat them.
Sleep deprivation: If you’re sleep deprived, the amount of sleep you need increases.
Sleep quality: If your sleep is frequently interrupted or cut short, you’re not getting quality sleep — and the quality of your sleep is just as important as the quantity.
Gender: There has been some interesting debate recently about gender differences and sleep. Do women need more sleep than men or the other way round? Women tend to require more sleep in the week before menstruation. On the other hand women tend to have flexibility to tolerate sleep deprivation that is often tested during pregnancies and baby years.
Types: Professor Him Horne has developed a larks and owls theory. According to this theory, the body clock of some people is set for early rising (larks) while owls tend to be late risers. The main difference lies in the energy levels throughout the day. Larks find it easier to eat breakfast and feel energetic in the mornings. Owls can find it hard to get going in the morning and can be grumpy. Larks are party poopers missing bed already at 10 pm while owls are only getting started. Yet most of us fall somewhere in between.
You can get your sleep profile in here (includes short analysis of lark vs owl):
To complicate things further, there is some evidence that some people just need more sleep than others. Einstein apparently needed 10-11 hours of sleep, whereas Margaret Thatcher famously only slept for five hours a night.
Many of us expect to go to bed and sleep without waking throughout the night. This is rather unrealistic expectation because the sleep is about elasticity (between different sleep stages as described above) and not about non-stop deep sleep. In fact, we are constantly rebounding between sleep and wakefulness. Getting angry and/or irritated at night because of waking up will only worsen the possibilities to fall back asleep quickly. Realizing the speed stages and accepting awakenings as part of normal sleep can radically speed up the nerves calm down and body system drop off.
Do you remember waking up last night? How many times? On average, a human being might wake an incredible 10-15 times a night! One theory relates back to caveman days when it might have been helpful to maintain a state of vigilance even while we slept, simply to avoid being eaten by predators.
For many, returning to sleep is the most challenging part (especially after two or three awakenings). However, progress can be made in all areas of sleep with different tools, tips and approaches.
Brains need sleep
The value of sleep is higher than ever before in the current information society. Brains need sleep at night to effectively operate during the day. During sleep the whole body, especially the brain, rebounds from the stress experienced during the day. When sleep is inadequate or non-restorative there will be challenges the following day with concentration and reaction ability. We will make mistakes and things don’t go right like usual. We feel irritated and can get provoked more easily.
During the deep sleep glycogen stores will be fulfilled. Interestingly, brains form only 3% of total body weight but they use 20-25% of total energy. We say that humans recharge their batteries during the night and it’s not far from the truth. This said, it good to know that there are also other ways to recharge our batteries, such as time with friends, rest, good food, entertainment, walk and sports and many other ways.