What is sleep?

Sleep is a state of human brain activity where the conscious connection to existence is broken. During sleep, the body recovers and rests, and for example heartbeat slows down and blood pressure drops. Only the brain works, as it processes the events of the day and recharges its own energy reserves.

Sleep stages are classified into dozing off period (N1 sleep), light sleep (N2 sleep), deep sleep (N3 sleep) and REM sleep.

A dozing person does not always feel like he is sleeping. In the N1 sleep, there are slow eye movements, and the brain’s 8-12 Hz alpha activity during wakefulness changes to 3-7 Hz theta activity. External stimuli, for example disturbing sounds, easily cause wakings. As a person who sleeps well, N1 sleep is less than 5 % of the night’s sleep. More than 10 % N1 sleep indicates poor sleeping quality.

In light N2 sleep, electrical activity of the brain slows further and there are observed 12-14 Hz sleep spindles, which are important for memory functions. N2 sleep makes up 35–55 % of the total duration of night sleep.

Deep N3 sleep (delta sleep) is the most important sleep. During deep sleep the energy reserves of the cells are filled, and the damage caused by the stress during waking hours is repaired.

In deep sleep, the brain’s energy reserves are also filled, and on the other hand, during wakefulness accumulated waste products are removed from the brain through the so-called cycle of the glymphatic system. The word “glymphatic” refers to the “lymph circulation” of the brain’s supporting cells, in other words glial cells.

According to the latest research, states of exhaustion in the brain, “brain fog” and also, for example, abnormal sleepiness causing Kleine-Levin Syndrome, could be caused by a disruption of the brain’s glymphatic circulation, whereby tiring waste products accumulate in the brain. Due to the long-term lack of deep N3 sleep, the glymphatic circulation can be disturbed, when amyloid also accumulates more easily in the brain. The accumulation of amyloid in the brain relates to i.a. memory disorders.

Deep sleep is also important for the conscious “hippocampal” memory. In deep sleep, a person “sleeps like a log”. Breathing is steady and pulse is calm. Deep sleep occurs most during the first third of the sleep phase (sleep time). For an adult who sleeps well, deep sleep is 15-30 % of the night’s sleep.

During REM sleep, brain and body are activated compared to slow-wave sleep: brain activity is intense, and breathing, heart rhythm and blood pressure vary. Even a healthy person can have breathing disruptions (apnea) during REM sleep. The day’s experiences and emotional states are organized and may repeat themselves. REM sleep is especially related to emotional memory and skill memory. It is also important for mental balance. Most eventful dreams are seen in REM sleep. During REM sleep, the brain metabolism is even more intense than when a person is awake. The eyes move quickly (Rapid Eye Movements) and the muscles are limp, but from time to time there occurs small muscle twitches. An adult who sleeps well has REM sleep for 20–25 % of the night’s sleep.

Antidepressants used to treat depression reduce REM sleep. Fatiguing antihistamines and very small doses of doxepin or mirtazapine, which block histamine-1 receptors, increase the amount of deep sleep without clearly affecting REM sleep. Benzodiazepines and many other sleeping pills can increase N1 and N2 sleep and reduce both deep N3 sleep and REM sleep.

The need for sleep and the sleep-wake rhythm

The amount of sleep a person needs varies individually. According to average values most people sleep 7-8 hours a day. In Finland, 4–12 % can survive on less than 6 hours of sleep (natural short sleepers), and 5–10 % need more than 9 hours of sleep per day (natural long sleepers) to be alert during the day.

Small children need a lot of sleep, and they also take naps. Teenagers should sleep even more than 9 hours a day, because at this stage of development, the second growth phase of the brain begins, and a lot of sleep is needed. In old age, the amount of night’s sleep may decrease, and nighttime awakenings may increase. On the other hand, in case of the elderly, napping partially compensates for shortened night sleep. A person has probably slept enough if he feels that the night’s sleep was refreshing when he wakes up in the morning.

Sleep is regulated by an internal circadian rhythm, which is synchronized by i.a. light, working life and various regular routines of the day. The rhythm can start to advance or delay individually, if it is not synchronized daily. In particular, morning light is an important synchronizer of the brain’s internal clock. The theme music of the evening

news tells the brain that it is 8:30 pm. In the farmhouse, the rooster’s crowing tells you that it is early in the morning.

Sleep-wake rhythm disorders are quite common causes of insomnia. For example, a delayed sleep phase is common for young people, where sleep does not come until the morning, and waking up in the morning is difficult. On the other hand, the level of alertness is at its highest in the evening. In an advanced sleep phase disorder, you go to bed already between 19:00 and 21:00, and wake up in the early morning hours and can’t sleep anymore.

People are also naturally either morning or evening chronotypes, which is good to consider when planning your own circadian rhythm. The sleep rhythm can also get messed up due to irregular working hours and when traveling from one time zone to another.

Sufficiently long sleep and the good quality of sleep are essential for health. A person has been able to stay awake without stimulants under experimental conditions demonstrably for 11 days. In 1964 sleep researchers of the Stanford University confirmed that californian Randy Gardner was staying awake by monitoring the electrical activity of the brain. Staying awake longer has also been reported, but there is no solid evidence for them.

The ability to function after temporary staying awake 24 hours continuosly corresponds to a 1 per mille alcohol intoxication and staying awake 36 hours corresponds to a 1.5 per mille alcohol intoxication.

Long-term sleep deprivation (lack of sleep and/or long-term poor quality of sleep) can cause central obesity. The continuous increase of waist circumference can be a symptom of poor quality of sleep or lack of sleep at night. Long-term sleep deprivation also increases the risk of developing adult-onset diabetes, metabolic syndrome and hypertension. According to some research, it is also a risk factor for myocardial infarction and cerebral infarction.

Lack of sleep weakens immunity. According to research, untreated insomnia and sleep apnea have increased the risk of a coronavirus infection and prolonged long covid. A significant and long-lasting (lasting several years) lack of sleep can also be a risk factor for depression and memory disorders. Potential untreated sleep apnea together with insomnia further increases such impairments.

Source: Hyvä uni 2023 (Magazine Good sleep 2023)/professor Markku Partinen

How to help your sleep – some general advice

If you can’t get so sleep in about 15 to 30 minutes do not panic. Instead of trying to sleep it is better to do something that helps you to calm down your mind. Consider reading a book or some magazine, but do not start to chat or write emails. Sometimes it is better to get up and walk into another room, drink a small glass of water, and maybe sit down on a chair and listen to relaxing music until you feel sleepy again. You may even look at television, but do not watch any exiting and activating programs. Note that television should not be in the bedroom unless you are a good sleeper and you do not suffer from insomnia. Do not try to sleep. This should help to associate your own bed and your own pillow with sleeping – and not with being awake in your own bed. If you stay in bed for extended periods of time, your system begins to associate staying awake and lying in bed together. Many people who suffer from sleeping problems begin to connect their anxieties and pains with lying in bed. The longer you stay awake in your bed, the stronger this habit becomes. It is known as harmful conditioning.

It can be difficult to get up from the comfortable warmth of your bed. You may feel very tired – but at the same time overactive, being unable to fall asleep. But remember. Do not stay in bed and let your mind to be active.

If you suffer from insomnia, make rising up at night easier and as comfortable as possible. Prepare yourself for a possible need to get up already the previous evening:

Leave a dim light in the next room and leave a blanket on an armchair or the sofa. You can also take along your own pillow and duvet.
Prepare something warm to drink into a thermos, maybe some water, milk, or caffeine free (e.g. herbal) tea.
You can listen to some music, maybe read or do something relaxing, but nothing that will awaken you more.
When you feel sleepy, go back to bed. If you still have trouble falling asleep, repeat the previous.
Keep following the instructions until you fall asleep.
Follow this protocol also if you wake up in the middle of the night and find it difficult to fall asleep again.
Short naps are healthy, but if you suffer from insomnia you should avoid having a long nap during the day and dozing off on the sofa or the armchair in the evenings.
A dedicated moment of worries works for both anxieties and sleeplessness
It is better to accept that you may have a tendency to worry about various things. It is better not to fight against such worries. Dedicating a moment for these worries is especially beneficial when you tend to think over the daily events, recent happening and/or the future as you go to bed. The goal is to end the daily events and happenings or future plans already in the evening. This should help you catch up your sleep. It is easier to sleep when you interrupt those chains of thoughts.

Reserve about 15 to 30 minutes to sit down, about two hours before going to bed. Take a sheet of paper and a pencil and write down things that worry you, how you feel, emotions and solutions that you think about – or even just daily events and things you have been doing. Make a note of any thoughts you have, even if no solutions have presented themselves. When you find a solution or a suggestion to a problem, work your way to solve it as far as possible. Do not worry overly much if it is something you cannot help yourself. You may need help from others, or just let time take care of it.

Doing this should help you feel in control over matters. You can decide yourself what you do with the notes. You can destroy the notes if you fear someone else will read them. Maybe burn the note to symbolise that you will not let the worries control you. You might want to read them out loud to give them some distance.

Don’t worry, if you get new ideas or plans into your mind as you are going to bed. Keep a note pad and a pencil by your bed. Write down the ideas or plans and return to them the following day. When you process various thoughts already during the daytime, it is easier to let go of them when you are settling down for the night.

If you wake up during the night and begin to think too much about something that has been worrying you, tell yourself, that now it is time to sleep and not ponder things. Tell yourself that you will get back to the matter the next day.

Circling thoughts

Think of stopping recurring/circling thoughts like you would apply a roadblock. If you have recurring thoughts in your mind, you may find a stop-word useful. It works most effectively when you have recurring, meaningless, and random thoughts going through your mind. These may crop up during the evening as you are settling down for the night or when you wake up in the middle of the night. To stop these thoughts bounding about in your head, decide on a stop-word. It should be something neutral and mostly meaningless, e.g. ‘and’, ‘that’, ‘but’, or something like those.

When you wake up in the middle of the night, it is best to use the word right away.  This helps to block the thoughts before you wake up fully and the alertness makes falling asleep difficult again. To stop random thoughts, there are three simple steps:

Repeat the stop word every two seconds or so keeping your eyes closed.
Do not say the word out loud. Repeat it soundlessly in your mind.
Keep repeating the stop word for about five minutes, if necessary.
Using the stop word should help you block the thoughts from penetrating into your mind. A person cannot think and say the word simultaneously. That is why the word must be something neutral and meaningless as it must not affect your feelings in any way.

Do not try too hard to get to sleep

Some people can’t fall asleep simply because they are trying it just too hard. Attempting to get to sleep too hard can cause grumpiness and frustrations; and they keep you from falling asleep. It is understandable that you want to sleep, and therefore you try to sleep even more. But – the harder you try, the more likely it is that you can’t fall asleep, or your sleep will not be sufficiently deep. Trying too hard can help your body to enter a hyperalert state. You can try concentrate to a specific relaxation method or reading, you can listen to music or try the paradoxical intention. You have slept well sometimes. We all have the talent by nature. It is now just time to learn it again.

Paradoxical intention

Take a comfortable position, switch off your lights. Keep your eyes open
Stop trying to fall asleep
Forget all your worries but remain awake
When your eyelids start feeling heavy and you want to close them, just think gently: “I’m staying awake for a few more minutes until I fall asleep naturally, when I’m ready.” If you can leave out the thoughts of falling asleep and sleeping, you will find that the sleep comes by naturally.

This technique will help you end forcing yourself to sleep. It also reliefs the anxiety about not falling asleep – again. When you are tired and follow this instruction, you will fall asleep naturally. It is good to wake up in morning and notice, that you fell asleep even after giving up. This should help you develop your self-confidence and aid in retrieving the natural sleep.