8 facts about sleep you probably didn’t know and why shut-eye affects every aspect of life

From scmp.com

From the science behind sleep paralysis to lucid dreams and memory making, experts help us understand little-known but vital aspects of sleep 

Little was known about sleep until modern science revolutionised our understanding. It turns out that what happens while you are unconscious dictates almost every aspect of your waking health, mood and brainpower.

While knowing how to get better sleep and why you need it is vital, the nocturnal world holds some interesting secrets. Here we look at eight things you probably did not know about sleep.

1. Testy times

If young men don’t get enough sleep, they have a level of testosterone that is equivalent to that of someone 10 years older, says British neuroscientist and renowned sleep expert Matthew Walker. That is because a big chunk of testosterone release happens while sleeping. Low testosterone levels affect energy levels and mood – and sperm production.

In women, too little sleep changes the way reproductive hormones are regulated, although the science is more complicated than a simple “less sleep equals less oestrogen” formula. They may experience a breakdown in the delicate monthly timing system that keeps their reproductive health and moods stable. Those who get fewer than six hours of sleep can see up to a 20 per cent reduction in ovulation-inducing hormones.

Lack of sleep disrupts our metabolic systems quickly. Getting only five hours of sleep for four nights in a row can negatively affect blood sugar levels, reducing insulin sensitivity to the extent that one could be classified as pre-diabetic, Walker says.

The immune system is also affected: restricting a healthy person to just four hours of sleep for a single night results in an alarming 70 per cent drop in the activity of natural killer cells – cytotoxic white blood cells that act as the immune system’s first line of defence.

2. Justice for owls

Some sleep scientists feel that modern society discriminates against those whose circadian rhythms – or internal clocks – make them night owls rather than larks who are up at the crack of dawn and go to bed early in the evening.

Since the Industrial Revolution in the 18th and 19th centuries, work has started early, and those who find it difficult to be in top form in the morning are looked down upon. This is considered unfair, as it is not possible to change your circadian rhythm.

A change in perception could be positive for businesses, Dr Stefan Volk of the University of Sydney Business School told this writer in a 2018 interview. Volk’s paper, “Chronotype Diversity in Teams: Toward a Theory of Team Energetic Asynchrony”, published in the Academy of Management Review, argued it would be productive to introduce a shift system so larks start work early and night owls start later, enabling everyone to work at their peak capacity.

Sadly for night owls, that is not on the horizon.

3. Memory making

Sleep is essential for forming memories; in deep sleep, bursts of activity in the hippocampus, which stores short-term memories, send information to the cortex, which stores long-term memories. Photo: Dreamstime/TNS

An important function of sleep is to consolidate memory; it turns short-term memory into long-term memory and stabilises new memories so that they stick.

In deep sleep, bursts of activity in the hippocampus, which stores short-term memories, send information to the cortex, which stores long-term memories.

The brain also cross-indexes memories and links them together during sleep, and adds new information gained in the day to what we already know by replaying recent experiences.

After a good night’s sleep, your memories will seem clearer and more coherent.

Sleep also consolidates learning by connecting facts into knowledge, notes Dr Barbara Oakley, a professor of engineering at Oakland University in Rochester, in the US state of Michigan, in her course “Learning How To Learn” on the online learning platform Coursera.

That is why a good night’s sleep before an exam is better than staying up all night cramming. Simply reading over your notes before going to sleep can be beneficial.

4. Connecting with the past

Dreams play an important part in our mental well-being. Sigmund Freud, the founder of psychoanalysis, believed the cause of a patient’s neurosis – usually a repressed traumatic childhood experience – could be determined by analysing their dreams.

That idea has generally been discredited, but sleep researchers still think dreams play a big role in our state of mind, changing our emotional relationship with our memories in a way that makes us feel better about them when we wake up.

The late sleep researcher and psychologist Rosalind Cartwright – known as the “queen of dreams” – said dreams are an important part of grieving and can take away the pain associated with the memory of a loss.

Through dreaming, we can gradually come to think of a deceased loved one more objectively, without the pain that comes with grief.

The same is true when something shocks us. If we see someone injured, or worse, in an accident or as the victim of a violent crime, dreaming will help us eventually be able to replay the event in our minds without the accompanying horror we felt when it occurred.

5. Dreams as therapy

The brain knows it is good for you to wake up in a calm mood, and uses dreaming to achieve that goal – dreams act as a kind of internal therapy.

“When all goes well, we awake refreshed with a modified strategy for guiding our behaviour,” wrote Cartwright in her 2010 book, The Twenty-four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives.

Dreams help the mind work through the emotional business of the day, away from the stress of waking life.

6. Fright night

During the transition between wakefulness and sleep, some people see ghosts and demons – or think they see them. While falling asleep, some become paralysed and sense an evil or macabre intruder in the room watching them.

Sometimes things get physical, and there are reports of women feeling like they are being sexually assaulted by a strange creature – an “incubus”, as they are called in mythology – while being physically unable to flee.

But as “anomalistic psychologist” Professor Chris French explains in his 2024 book The Science of Weird S***, there is nothing supernatural in play; it is a well-documented scientific phenomenon called sleep paralysis.

This occurs when the mind is awake but the body is sleeping. Dreams occur mainly in REM (rapid eye movement) sleep, when the body is paralysed to stop the sleeper physically acting out those dreams – a state that is called REM atonia.

Due to a biological glitch, the paralysis can occur while the mind is awake.

Psychologist Chris French explains the science of sleep paralysis in his book The Science of Weird S***. Photo: gold.ac.uk

Researchers suggest the demons appear because we have evolved to subconsciously monitor the outside world for threats at all times while we are awake. Our brain is still focused on this task during sleep paralysis, but it becomes confused by the situation and invents the demons.

French says that few doctors are aware of sleep paralysis, and many people suffer unnecessarily because they think they are going mad – or really seeing evil intruders.

7. Living the dream

It is possible to control your dreams and influence their direction. This is called “lucid dreaming”, a term coined by Dutch psychiatrist Frederik van Eeden in 1913 in the journal Proceedings of the Society for Psychical Research.

The ability comes naturally to some people, although others have to practise by keeping dream journals to train the brain. Essentially, sleepers become aware they are dreaming, and some then consciously take control of the dream.

As with sleep paralysis, it is believed to be made possible by the interplay between REM sleep and wakefulness, although scientists are still figuring out how that works.

Some enjoy lucid dreaming and find it useful in inspiring creativity. It may even have been a factor in The Beatles’ classic song “Yesterday”. Paul McCartney is reported to have composed the melody for it after hearing it in a dream. Upon waking, he immediately played the tune on a piano next to his bed to capture it before it faded.

8. Moving for better sleep

Research suggests that tai chi and yoga can help you sleep and stay asleep for longer.

Tai chi practitioners can extend their nightly sleep by more than 50 minutes and can fall asleep 25 minutes faster than non-practitioners, according to a study published in BMJ Evidence-Based Medicine.

Yoga can add up to two hours of sleep each night and reduce the number of times you wake up.

In a similar vein, a study from the University of Hong Kong found that tai chi may provide as much relief as talk therapy does for those suffering from insomnia. 

The next time you are tempted to stay up a little later when it is time to turn in, remember that sleep is much more than a passive break from reality. It is an active, dynamic state in which our minds heal, memories lock in and bodies reset.

https://www.scmp.com/lifestyle/health-wellness/article/3359982/8-facts-about-sleep-you-probably-didnt-know-and-why-shut-eye-affects-every-aspect-life