Sleep better, live longer (what is your sleep debt? )
In this article, we will firstly talk about basics of sleep phenomenon and then about sleep disorders, primarily about sleep deprivation. The purpose of this article is to point out the importance of good sleeping.
Before we discussing how sleep deprivation (negatively) impacts brain, let recall basic facts about sleep cycles (see video "Phases of Sleep" below as well). First of all, sleep is divided into two types: rapid eye movement (REM) and non-rapid eye movement (NREM). The basic physical characteristic of REM sleep is – as the term suggest – eye movement while most muscles are paralysed. It is the stage of intensive brain activity, that is accompanied by dreams. We reach REM a few times during the night. Letter half of the night is more dominated by this type of sleeping.
NREM sleep consists of three stages, marked as N1, N2, N3. Stage 1 (N1) is a stage between wakefulness and sleep. Basic characteristic of brain activity in this stage are theta waves, with low frequency. It is quite easy to wake up person in this stage of sleep. After approximately 5 minutes in this stage, a person enters the stage 2 (N2). Basic characteristics of this stage are spindle in waves and K-complex (that has high amplitude). It is still relatively easy to wake up person in this stage. After some 10 minutes in this stage, we come in into the next stage of sleeping (N3), entering the world of deep sleeping. It is known that it is hard to wake up person in this stage of sleep. Our brain is busy with delta activity. One of the basic function of this stage is to repair and to built new cells and tissues. Delta waves has high amplitude and low frequency – less than 3.5 Hz. Psychologists differentiate two kind of this stage, the second being called simply stage 4.
Sleep process consists of cycles of REM and non-REM sleeping. More precisely, a cycle is a sequence of N1 – N2 – N3 – N2 – REM types of sleeping. During the night there are usually four of five such a cycles. During the lifetime we spent about 6 years dreaming!
sharp rise in blood pressure
melatonin secretion stops
fastest reaction time
highest body temperature
melatonin secretion starts
lowest body temperature
Sleep disorders – epidemic of modern society
It seems that in our modern time everybody is in a lack of a sleep. When in the morning we go to the office we can hear comments like “I don’t function before my first coffee”, “I’m so sleepy”,… Majority of us need stimulants to begin the day and stay awake during the day. Even with help of a good coffee or tea we may have difficulty with concentration in our work spot. This phenomenon is so widespread that some professionals and scientist use term epidemic to emphasise this veiled problem.
However, while sitting sleepy and feeling drowsiness in a safe office might don’t seems like a severe problem, our associations became quite different if the office would be replaced by a car, for example. Unfortunately, there is much more accidents caused by sleep disorder than it would be said.
Books representing newest scientific knowledge about sleeping bring unkind stories of real disasters caused by human sleep disorders in order to influence the modern society which have still ignored this problem.
How long did you sleep the last night?
One of the essential rules related to sleeping is the fact that our brain remembers shortage in a sleep, counting that into “sleeping debt account”. So, if during a week we reduce our sleep constantly for 2 hours, after seven days our debt will be 14 hours, assuming at beginning of this period there was no any debt – which is not too realistic.
Let’s imagine the person who in general needs 8 hours of sleep to feel good and normally alert during the next day. However, when he or she is extremely busy, there is no another choice than to finish the tasks late in the evening after finishing all family and similar obligation. Let say this means going into the bad one hour after the midnight and sleeping the next 5 hours. Of course the person will be very sleepy the next day but without possibility to take a rest. Finally, when the day will be over, the person will go towards the bad with smile and probably will fast asleep. After a 8-hours long sleep the person wake up with mind “O, such a good sleep, I feel rested”. However, on the “sleep account” there still will be 3 hours deficiency, which must be recovered (by 3 additional hours of sleeping) if the person wants again meets they full energy and eagerness.
So, does it mean that the brain persistently remembers all our debt don’t forgiving no one hours? If all late hours from our student’s days are still in the account we are really in a trouble. :-) Well, it can’t be said precisely how long the debt is remembered: for sure every lack of sleep is remembered 2 weeks; whether is it remembered more that 2 weeks – this is scientifically not clear yet.
More precisely, always when we are awake, sleep deprivation is collected: in an ideal case if we woke up without debt, until the sleeping time we collect just around 8 hours of sleep deficit. If it has all our debt, we normally wouldn’t sleepy during the day because of acting one another mechanism -biological clock. In that sought case, although having a debt we are not sleepy because biological clock enhances our watchfulness.
But when the debt is severe pressure of sleepiness is higher than acting of biological clock.
The fact presented in this article are based on books written by professionals, including the one linked below. However, contrary to this article (at least on the first sight)... Reportedly, somewhere in Spain there are monks who usually sleep 6 or 5 hours per night. Moreover, masters among them sleep only some 4 hours...
How to measure the debt?
Might you now ask ourselves what is your sleep debt? Zero, 2 hours, 10 hours,… ? Well, it seems that in average it is higher that we would say. In one experiment participants have they normal routine during the main part of the day while they were asked to get back to laboratory room in late afternoon where they spent the night. The rooms were comfortable but without any content like newspaper, radio or something. Since there weren’t any stimulants, participants firstly slept significantly more than 8 hours.
Some researches have found that people having siesta are more efficient.
Siesta is a short rest including sleep in the early afternoon, typical for hot countries.
However, it is important the rest be in the early afternoon, otherwise it can cause sleeplessness.
However, after a while they catch more or less constant figure of around 8 hours of sleeping.
The sum of extra sleep in first several days was around 30 hours per participant, presenting the sleep debt repayment.
But we don’t need to perform such a test in order to establish our sleep debt. There is a simple, intuitive rule: the more we are sleepy the more sleep we miss.
It seems that relation between debt and sleepiness is almost algebraic, in some medical research it is noticed that the time needed to fall asleep (once when somebody is put in environment without stimulants) matches the length of missing sleep.
However, as we know, a special medical environment is not imperative to achieve such an atmosphere but our common daily ambient like car or office can be relaxing enough to give in to the pressure and send us into the dreams – possibly causing the problems.
Phases of Sleep
A good sleep is very important for both our health and our efficiency. The open encyclopedia Wikipedia, in the article “Sleep” lists more than 15 problems or diseases that can be caused by sleep deprivation, from the problems like irritability or severe yawning to the more serious risk of heart disease or impaired immune system. The main massage of the book “The Promise of Sleep”, by scientists W.C.Dement and C.Vaughan, would be “sleep better, live more”.
How much deficit of sleep did you collect for the last two days?
This very inspiration book teach us how to understand sleep and how to cope with sleep disorder. The book is written in a scientific-popular style by the authors with a great research experience in sleep phenomenon. Sometimes the authors also include their personal experience. Maybe it sounds like a joke, but the author says that he used to cancel dinners in order not be late – for sleeping. Very useful book for the improvement of our lives.