The Science of Sleep

If you are struggling to get enough restful sleep then perhaps it’s time for you to become a sleep scientist. If you ask a person who sleeps well what steps they take to get a good night they will probably not have a clue. Ask the same question of an insomniac and you will get a two hour Power Point presentation! We owe it to ourselves to understand what is happening to our bodies and minds and how a good night sleep affects us on a cellular level. So put on your lab coat and spectacles and lets do the science bit together….

Insomnia is defined as difficulty falling asleep or sustaining sleep for more than a few hours without waking. Its opposite but equally tiring condition is hypersomnia – sleeping for long periods but waking still feeling tired. Most of us will occasionally experience ‘unrestful’ sleep, but for some, the bad nights outnumber the good. Once you have had a few poor nights, the anxiety about how the next night might go actually feeds into the inability to relax and fall asleep. And once you’re stuck in the cycle it can be very difficult to break free. So how do we know if we are getting enough sleep? And what is the optimum amount of sleep? Some people are bright eyed and bushy tailed on just three hours, whilst others need a solid ten just to feel human. It turns out that each and every one of us has different sleep needs and these change throughout the life cycle. The most effective way to measure the quality of your sleep is by the effect it has on you the next day. If you feel well-rested when you get up and have plenty of energy to get you through the day, then you have nothing to worry about. If however you are are battling fatigue most of the day, or struggling to concentrate or feeling emotionally wobbly or worried about how you are going to cope, then there is a possibility that you are not getting enough sleep.

Not all sleep is created equal
We tend to think of “awake” and “asleep” as polar opposites like black and white. In reality sleep is more complex than this: there are times whilst we are asleep that we come very close to waking (this is when a sudden sound might wake us) and times when we are awake that we skirt very close to sleep (we experience this as ‘zoning out’). So instead of seeing awake and asleep as polar opposites with no middle ground, we could visualise them more like a yin-yang symbol: a little bit of light in the dark, and a little bit of dark in the light. If you use a fitness tracker (often worn on the wrist like a bracelet) you will already know that through the night you move through different types of sleep.
Put very simply, we can think of sleep as having three phases: light, deep and R.E.M.
LIGHT SLEEP: occurs throughout the night
Stage 1:
 Your sleep is shallow and not particularly restful, but it’s usually a quick transition to the next phase, so you’re not in it for very long (think of it as the equivalent of pulling away in first gear in your car, it just gets the journey started). You can still hear things and have some awareness of your surroundings so may not believe yourself to be asleep.
Stage 2
Your sleep is a little deeper than stage 1 but you could still be easily woken. Your breathing and heart rate decrease slightly during this stage.

DEEP SLEEP: occurs primarily in the first half of the night
You are now much less responsive to outside stimuli and would be difficult to wake. Your breathing slows down even more as does your heart rate which becomes very regular with fewer fluctuations. Your muscles are very relaxed. Deep sleep is very much about the body as the ‘thinking parts’ of your brain are largely offline. This is when your body secretes the hormones associated with cellular repair which is why getting sufficient deep sleep is thought to strengthen your immune system.

R.E.M Sleep: occurs more in the second half of the night
In the same way that deep sleep is about your body, R.E.M sleep is about your brain which is very active during this phase. Your muscles are now completely inactive to the point of paralysis. R.E.M is when most dreaming happens and your eyes move rapidly in different directions (hence the name). Your heart rate increases and your breathing becomes more irregular. R.E.M is essential for the regulation of emotion and also for memory, as this is when your brain is clearing out and sorting data, and shifting some of it into your long term memory. It is also the peak of protein synthesis at the cellular level, which keeps many processes in the body working properly.

However your sleep is not a linear progression from light sleep to deep sleep to R.E.M. Instead sleep operates in cycles each lasting on average 90 minutes. Each cycle contains different proportions of each kind of sleep. Different people need a different number of cycles of sleep to wake feeling refreshed. During the second half of the night the cycles break down and you alternate between light sleep and R.E.M for the rest of the night.

Your sleep is made up of:
50% or more of light sleep
10—25% deep sleep
25% R.E.M sleep

Getting enough deep and R.E.M sleep is what refreshes you. Your deep sleep can be disrupted by pain, so many medical conditions such as arthritis can affect deep sleep as can the pain from injuries and illnesses. Shift work can affect your ability to achieve deep sleep as does age, we get less deep sleep in our later years. If your sleep is cut short for any reason, you will be losing out on R.E.M sleep and this can leave you feeling groggy, less able to focus, and can affect the functioning of your memory.

Although the deeper phases of sleep are essential for your health, they are also when you are at your most vulnerable. Think about it, during deep sleep your brain is almost completely shut down, and in R.E.M sleep your body is all but paralysed. You are extremely vulnerable in both these states as you would be difficult to rouse and slow to react as your body and brain would need to come back ‘on-line’. So we begin to see the value of the sleep cycles. If you were to have all of your deep and R.E.M sleep in long blocks,you would be more likely to sleep through an emergency situation which could prove a threat to your safety or even your life. Instead, as soon as your system completes one cycle of tasks you are switched quickly back to light sleep, meaning that you could wake easily and quickly if needbe. The problem arises when you are woken in this light phase of sleep by an outside stimuli that poses no real threat to you, like a neighbours security light coming on, or by an internal stimuli such as a worry. It might help to think of your light sleep as a security guard doing the rounds, between bouts of deep and R.E.M sleep, thus keeping you safe. I find this thought reassuring when I do have periods of night wakefulness. What we can do is optimise our opportunities to achieve these deeper states of sleep so that this essential maintenance work can be carried out by minimising the chances of being woken during our light sleep. (More on this in the next article “Unlocking Sleep”).

History Lesson
If we had records going back to our most ancient ancestors , I wonder what we might learn about sleep. Were we sleeping through the night as cave-dwelling people? Were we sleeping in groups perhaps with someone on ‘Night Watch’ to keep us safe? It may surprise you to know that the records we do have show that night waking is a normal phenomena. Humans have not always been awake all day and asleep all night. Like many other animals, (and indeed baby humans) we would naturally have periods of wakefulness in the night and naps during the day.

We can pinpoint a real shift in sleep patterns following the Industrial Revolution (around 1760). With machines beginning to replace manual labour, and the work place moving out of the home and into the factory, people were expected to work all of the hours required of them in one block of time with minimal breaks. The expectation became that the human ‘machine’ could work ceaselessly and produce a consistently high standard of work with minimal maintenance. This meant no more naps during the day and created the need for sleep to happen in one solid block at night.

Further advances such as the invention of electric light meant that the working day could be extended. Imagine for a moment living without electricity. For those of us with full sight we are so dependant on our eyes that almost all activity would have to stop the minute it was dark. Now our working day is more likely to be sat at a desk in artificial light than outdoors or in a factory , but we are still expected to perform like machines, working seamlessly for eight hours or more at a time with no fluctuation in our output.

Recently there was another technological advance that has played havoc with many peoples sleep patterns. Electric light used to be incandescent, a warm yellowish colour. In 1997 this changed as blue light emitting diodes (L.E.D’s) were developed. These use much less energy and have a much longer life span, but this blue light is the type we humans are most sensitive to. It is TWICE as effective at suppressing the release of sleep hormones as the old incandescent light was. In 2020 another shift occurred. As a consequence of the pandemic many peoples work place moved back into the home. We do not know as yet whether this trend for working from home will continue for the foreseeable future if it proves to be more cost effective for some businesses. If more people are able to work from home then perhaps a more flexible working day could evolve. Could this signify a return to a more natural sleep rhythm for some of us?

Night and Day

We are designed to fall asleep when it gets dark and wake up when it gets light. The presence or absence of daylight causes our bodies to produce specific hormones, some to wake us up and keep us awake and some to make us fall asleep and stay asleep. The extension of daylight hours made possible by artificial light, and the fact that more of us work indoors during the day, has tampered with our normal cycle of sleeping and waking.This is known as our Circadian Rhythm, natural internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours. People who work shifts, or travellers who cross time zones, may experience sleep problems simply because they are trying to sleep when their internal clock is telling them it is daytime. This gives us some valuable data – it takes time for us to adjust to a new sleep rhythm. It is important that we have a realistic expectation of the time frame required to improve our sleep patterns. It will probably not happen overnight, especailly if your sleep has been disrupted for a long time. Take some solace from the knowledge that you are designed to move back into a state of balance, so unless this mechanism is beng blocked, possibly by an underlying medical condition, the potential exists within you to re-establish a good sleep pattern and get the rest that you need and deserve.

In the next article “Unlocking Sleep” we will start to look at practical ways to improve your sleep

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