Mysterious Sleep, What You Need to Know and Why Our Ancestors Were ‘Insomniac’
Ancient sleep
Throughout centuries we had various ideas of what sleep is and why we may or may not need it. Ancient Greeks and Romans had their god of sleep and dreams – Hypnos. He was the son of Nyx (night) and a twin brother of Thanatos (death). Hypnos was seen as a remover of all pain and suffering.
Ancient Egyptians interpreted and analysed dreams many centuries before modern psychoanalysis. Sleep was used as one of the methods of healing in special sleep temples. Ancient Egypt was also a place that first mentions sleep disorders and ways of treating them, which is documented on few survived papyri dealing with the ancient Egyptian medicine. First insomnia medication was prescribed by the Egyptians. They used poppy seeds (opium) as an anesthetic and as a treatment for insomnia and headaches.
Professor Roger Ekirch did a lot of research on pre-industrial sleeping patterns. He documented that in early-modern Europe and North America there were two sleep periods interrupted in the middle by an hour or more of activities – praying, meditation, reading, sex. There was a first sleep, called ‘dead sleep’, and the second one called ‘morning sleep’. The modern insomnia – waking up in the middle of the night, reading a book, wondering for few hours, was a common practice in pre-industrial Europe. According to professor Ekirch our segmented sleep is our natural, evolutionary heritage, which has been disrupted by industrialisation and electricity.
What is sleep?
It’s very hard to define it, even though sleep is such a vital process. There is still a lot we don’t know about sleep and scientists are still exploring sleep and dreams. Sleep fulfills basic biological needs in our brain and body. We need sleep to function well, to restore our energy.
People used to think that sleep was the time for the body and brain to shut down to get ready for the next day. Recently scientists discovered that this could not be further from the truth. Our brain needs sleep to process information, to repair and maintain brain cells and remove toxins. Our body also needs to recover and regenerate, especially our cardiovascular system. Sleep is crucial for us to maintain focus, attention and alertness. We also need dreams.
The Biological Clock and Homeostasis
Sleep is driven by two processes in our brain and body – circadian rhythm and homeostasis. Circadian rhythm is our biological clock. It’s our internal process regulating the sleep-wake cycle and repeats itself roughly every 24 hours.
Every living thing has its own circadian clock – plants, animals and even bacteria. Body temperature, hormone levels, blood pressure, concentration, muscle tension and performance – all these processes are driven and changed by the biological clock. Our circadian clock is affected by the environment we are in, it’s sunlight and temperature.
The second process that regulates sleep is the process of sleep-wake homeostasis. The drive for stability and balance in our body. Homeostatic need for sleep is growing through the awake stage and should be the highest in the evening, when we have been awake for a long time. Circadian rhythm and homeostasis need to be in tune in order to induce sleep.
We can best see the effects of the relationship between circadian rhythm and homeostasis when it is disturbed, night workers are a prime example. At night, the signals that stimulate the brain to be awake like daylight or higher temperatures are not present. Also in the morning, when they are trying to go to bed, their brain and body get confused by daylight and the raising temperatures. Homeostasis tells the brain that they have been up for long enough and it is time to sleep, yet the circadian rhythm tells their body that it is time to get up. This means that night workers may find it more difficult to fall asleep, leading to less overall sleep.
What happens when we sleep?
There are four different stages of sleep and we go through them is cycles. Sleep cycles last around 90 minutes and we go through a few of them in each night.
Stage One
The first stage of sleep that is a changeover from wakefulness to sleep. Our brain waves begin to slow from daytime wakefulness patterns, we start to produce alpha and theta waves. Our heartbeat, breathing and eye movements slow down, our muscles relax with occasional twitches. We call this stage light sleep as we remain somewhat alert and can be easily woken. This stage is relatively short (lasts several minutes).
Stage Two
Stage two – this stage is also fairly light sleep before we enter deeper sleep. Our heartbeat and breathing slow and muscles relax even further. Our body temperature drops and eye movements stop. Our brain wave activity slows, but also produces a sudden increase in brain wave frequency (sleep spindles).
When we have a ‘power nap’ we would go through those first two stages and then wake up.
Stage Three
Stage three – deep sleep, the much-needed stage for us to feel refreshed in the morning. It occurs in longer periods in the first half of the night. Our brain produces even slower delta waves and we don’t experience any eye movement. Our heartbeat and breathing slow to the lowest levels during sleep. Our muscles are relaxed and it might be difficult to wake us up as our body becomes less responsive to outside stimuli. In this stage, our body repairs muscles and tissues, stimulates growth, boosts our immunity and builds up energy for the next morning.
In some sources, this stage is broken down into stage three and four – where you have the deepest restorative, refreshing sleep.
REM Stage
In REM (Rapid Eye Movement) stage, we generally enter this stage around 90 minutes after falling asleep. An average adult has five or six REM cycles each night. During this final stage of sleep, our brain becomes more active. Mixed frequency brain waves activity become close to than when we are awake. Our breathing becomes faster, irregular and shallow, our heart rate and blood pressure increase. Our body temperature falls to its lowest point. Our eyes move quickly in different directions (hence the name).
Most of our dreaming occurs during REM sleep. We might get very vivid and bizarre dreams in this stage. Our arm and leg muscles become temporarily paralysed, which luckily prevents us from acting out our dreams.
REM stage is very important in learning and memory function. It enables the brain to consolidate and process information from the day before, so it can be transferred into our long-term memory.
Dreaming
We all dream and spend about 2 hours each night dreaming, but we might not remember it. We don’t quite know the purpose of dreams. Some scientists think dreams can help us process our emotions or memories, while others think dreams are just a result of random activities in the brain. Events experienced during the day can often affect our thoughts during sleep and often people suffering from stress or anxiety are more likely to have scary or frightening dreams. We can experience dreams in all stages of sleep, but usually have the most vivid dreams in REM stage. Some of us can dream in colour and others can only remember their black and white dreams.
Conclusions
Sleep is vital for our brain and body, for restoring and processing, for our immune system. So all around a crucial and necessary process. It is also an automatic process, so we don’t need to worry about trying to switch it on or control it. It happens automatically.
We might have difficulties with our sleep from time to time, or a chronic sleep problem. I will write about tackling sleep difficulties in further articles.
You can find more information on sleep and some helpful techniques below.
Mind.org – How to cope with sleep problems
Asaad, Tarek. (2015). Sleep in Ancient Egypt
Virginia Polytechnic Institute and State University – Department of History – “Sleep We Have Lost“