Sleep is the vital balm that restores us after a long day of work and play, and prepares us for the next. How we feel at day is largely determined by how well we sleep at night.
Sleep has a vital role for our health and creative energy. Sleep is involved in how we heal and repair our blood vessels and sleep deprivation increases the risk of cardiovascular disease, kidney problems, high blood pressure, and diabetes.
Sleep is also involved in the balance between the two hormones that make us hungry (ghrelin) and saturated (leptin) and sleep deprivation increases the risk of obesity in both young and adults. Sleep also facilitates normal growth in adolescents and by affecting our immune system and our hormone balance, it helps keep us healthy throughout the years.
Sleep is not a constant and passive state but is characterised by four different stages of a sleep cycle; falling asleep, stable sleep, deep sleep and dream sleep or REM sleep (REM stands for rapid eye movements).
Each such sleep cycle is approximately 90 minutes long, and repeated during the night with longer periods of REM sleep in each new cycle; from 5-10 minutes at the beginning of the night to half an hour or more in the last cycle before waking up.
The longer you have been awake, the faster you fall asleep and deeper sleep. The body recovers most during deep sleep, as the brain’s activity is at low speed and the secretion of stress hormones is the lowest. Good sleep also leads to improved memory features, a good mood and increased creativity.
During sleep, we consolidate our memories from the previous day, but we also integrate these memories in a broader context and create new links to previous similar memories. If we have been to a concert, the brain, when we are asleep, connects these memories to our experiences from previous concert visits or the music to the memories of other music we have heard. If we’ve been there with a certain person, there are also connections to memories of other contacts we had with this person.
Consolidation of our memories is a complicated process over the course of several nights. During sleep, the different memory fragments are built into meaningful concepts, but memories can also be repaired and enhanced so that when we wake up, we’ve actually improved our ability, whether it’s factual skills, mathematical problem solving, or music or sport skills. The sleep also allows us to distinguish new previously hidden rules or abstractions, such as grammatical patterns during language learning. These positive memory effects of sleep are mainly related to activities that have touched and engaged.
This memory consolidation occurs mainly during the first 90-minute cycle and the last period of REM sleep in the morning. Alcohol or sleepiness that affects sleep or premature awakening can seriously interfere with memory consolidation, and what you lose during one night can not be compensated for by more sleep the following nights. On the contrary, one night without sleep also causes memory consolidation for the next 2-3 nights when the brain tries to restore normal daily rhythm.
The need for sleep is for most adults somewhere between six and nine hours, with a greater sleep need in children. We need to sleep, but not necessarily in one stretch. Throughout history, our natural sleep patterns have largely been controlled by the daylight and a sleep pattern with two-night periods of night sleep, combined with a slumber at day, is more natural than the eight hours in a row that has become the norm since the course of industrialisation and the introduction of the electric light.
Sleep deficiency causes slower brainwaves in the browsers, lack of attention, anxiety, memory impairment and an irritated mood. Longer sleep deprivation causes mental, physical and emotional fatigue. People who have been without sleep for 32 hours show a severe and prolonged reduction in ability of diverge thinking compared to a control group who has been sleeping.
But also a few hours lack of sleep is affecting performance the following day in a clearly negative way. We risk dozing off for short micro sleep moments without even being aware of it, which may be fatal in traffic. Many major disasters, such as nuclear accidents in Chernobyl and Three Mile Island, the Exxon Valdezoil tanker spill, have been caused by a lack of sleep among the responsible personnel.
To stay up and study the night before an exam is a bad tactic. But too much sleep can be negative, albeit not as much. So the best habit is to try to have a regular daily rhythm, whether it’s weekdays or weekend, with night sleep that gives enough rest to feel well rested when waking up in the morning.
Tips: There are a number of well-proven tricks you can use if you have trouble sleeping:
- Go to bed at the same time each evening. We have an internal biological clock that used to be controlled by the seasonal changes before the introduction of electric light. If you have different sleep patterns on weekdays and weekends, you will experience a constant jet lag. Also try to get up at about the same time each morning. The only reason to sleep longer is if you have a “sleep deficit” from earlier for short nights.
- Take a bath a couple of hours before going to bed. The chill that the body feels when you getting up from the bath signals to the body to slow down. Alternatively take a “light” sauna just before going to bed so that your body is pleasantly warm and relaxed.
- Avoid mental efforts just before going to bed. Problem solving, detective stories or a horror movie on Tv gets the brain in high speed. Better then to listen to quiet music in front of the fire place.
- A short walk just before you go to bed will both lower your brain activity and give you some fresh air. On the other hand, avoid a hard physical pass hours before bedtime otherwise you have an excretion of the activation hormone cortisol and adrenaline that aggravate the insomnia.
- Avoid energicing substances. Coffee, tea and chocolate contain stimulating xanthines. Alcohol may cause drowsiness, but it often leads to a shallow and unrestful sleep. Warm milk containing tryptophan (a substance that the body transforms into the relaxing hormone serotonin) is a better option. Also, avoid eating just before you go to bed – especially food containing fat and sugar.
- Let the bedroom be a place only for sleep (and sex). If you also use the bedroom and the bed for work and other activities, your brain will also associates it with these habits. Keeping the room “free” from unnecessary activities gives a conditioned reflex to sleep when you lay down. The bedroom may also be a few degrees cooler than the rest of the home.
- Avoid sleeping pills. Regular medications to fall asleep, almost always lead to addiction. After a while, their initial effect decreases or ceases, as you get accustomed to them, but if you the try to quit them, you may experience worse insomnia than before you started taking medication.
For those who have the ability to control their sleep rhythm, it may be worth exploring the effects of two sleep periods during the night, but also taking the opportunity to have a half an hour nap in the middle of the day. In order for this to work, you will need to reach the stable sleep, which takes about 20 minutes.
The American Space Agency, NASA, has demonstrated that pilots who took a 40-minute nap during long-haul flights increased their ability by 34% and their physical alertness by 100%.
- National Heart, Lung, and Blood Institute. Why Sleep is important? https://www.nhlbi.nih.gov/health/health-topics/topics/sdd/why
- Walker PW & Stickgold R (2010). Overnight Alchemy: Sleep-dependent Memory Evolution. Nature reviews. Neuroscience 11:218.
- Home JA (1988). Sleep loss and “divergent” thinking ability. Journal of Sleep Research & Sleep Medicine. 11:528–536.
- Levitin Daniel (2015). The organized mind: Thinking straight in the age of information overload. Penguin Books.
- Martin Paul R (2003). Counting sheep: The science and pleasures of sleep and dreams.
Detta blogginlägg på svenska