Since ancient times, sleep was perceived as a mysterious condition, state of unconsciousness in which dreams can occur, and since the beginning of time people had problems with understanding and explaining how and why this happens to us every night. Even today, when we have all technological achievements and laboratories, scientists are still working hard on the unraveling of sleep mysteries, and they are coming to new conclusions every day, but again, sleep remains one of those areas in which many things are yet to be discovered and explained.
One of the most philosophical sleep questions remains, why do we sleep? It was listed as one of the 100 questions that are not answered by the American Association for the Advancement of Science (AAAS). Some of the sleep-related topics that remain unclear are causes of parasomnia, dreams, effects of long and short sleep, the function of REM sleep, hibernation, how our memory works, and many, many more. In today’s post, we are going to discuss a few of these sleep mysteries.
Why Do We Need to Sleep?
You may believe that sleeping is overrated but anyway you will have to sleep at some point since it is inevitable. If our body and brain are forcing us to fall asleep, then it must be a mandatory part of their normal functioning. We may sleep for three hours or nine hours and go on with our day feeling tired, but our body is somehow programmed that it needs those six to eight hours of sleep per night in order to function normally. But why does it take that specific period of time? Researchers have found out that that number of hours is the most optimal for us, and there will probably be no way to shorten that time.
Even though while we are sleeping we are not doing any activities except occasional movements, our brain, and internal body organs are highly active and perform many restorative processes, hormones are being released, heart rate and blood pressure are regulated, and so on. How exactly this occurs and why and how our body is programmed to function this way is still a mystery in some way. Scientists are aware that sleep and its restorative processes are key to our wellbeing, but they have not figured out how it all functions yet.
What Causes Parasomnia?
Parasomnia stands for a group of sleep disorders such as sleepwalking, sleep paralysis, sleep aggression, nightmares, sleep-related eating disorders or REM sleep behavior disorder. Parasomnias include a wide range of undesirable movements, behavior, emotions, dreams or perceptions. Apparently, many of these disorders have a negative impact on sleepers daytime, but science is struggling to provide enough solid pieces of evidence about what can cause them.
It is believed that genetics play a key role since parasomnia usually runs in families, but for some types of parasomnia, even brain disorders can be responsible, for example for a REM behavior disorder. Many medications or other sleep disorders can also trigger parasomnia which affects around 10% of the US population.
People of all ages can experience parasomnia, but children are the most liable age group since the immaturity of their brain puts them at higher risk of parasomnia. Good news is that as children get older, this disorder usually disappears on its own without leaving any consequences on the children’s health.
How Sleep Impacts Memory?
Getting too much or too little sleep can negatively affect your memory, but how that happens and how can we determine the perfect amount of sleep? It is believed that recommended seven or eight hours of sleep can help you maintain a good memory later in life.
One study gathered information about the sleep habits of a group of women in 1986., and in 2002., and interviewed them three times after that about their thinking skills and memory. They find out that brains of participants who slept more than 9 or less than 5 hours per night had worse test performances than the ones from participants who were sleeping around seven hours each night. They also came to the conclusion that so-called undersleepers and oversleepers are usually mentally two years older than the sleepers who slept for at least seven hours per night.
People who are chronically sleep deprived are more likely to make mistakes, accidents, to forget what they need to do because their brain functions are slower. Some long term consequences of sleep deprivation include memory problems, although it has not been figured out how exactly are those two things correlated.
Some memories are based on facts, and some are episodic and attached to some events from our lives, while others are instructional (riding a bike, playing piano, etc.). In order for something to become a part of our memory, it has to go through these three stages:
- Acquisition – experiencing or learning something new
- Consolidation – once the memory of an event becomes stable in our brain
- Recall – the ability to access that memory in near or further future
Recall and acquisition both occur while we are awake, but sleep researchers believe that for consolidation of memory, regardless of her type, sleep is essential and required. Because without an adequate amount of sleep, our brain will have troubles with absorbing and recalling memories.
Some studies that included memory tests have shown that people who were sleeping the night before performed better in many fields.
Genetics and Sleep
Scientists believe that some sleep disorders are genetically transferred to family members and that our genes can determine the amount of sleep that we need. In a recent study, scientists were able to identify a human gene DEC2 that has an essential role in body’s natural sleep-wake cycle, and mutations of that gene can result with very short periods of sleep.
Researches were following sleep habits of a family with a mutated DEC2 gene. All family members were going to bed around 11 PM, and they would wake up on their own around 5 AM. This family had low sleep requirements, but surprisingly that did not have any negative consequences on their everyday functioning, that was their natural sleep cycle. It is considered that less than 5% of the US population has this unusual condition.
Sleep disorders that can run in families include dyssomnia, which stands for a wide range of sleep disorders including narcolepsy, sleep apnea, insomnia, and hypersomnia, or any other disorder that affects the ability to fall or stay asleep.
A study from 1972. examined the families of patients who were diagnosed with narcolepsy or insomnia. After a series of questionnaires and clinical examinations, the study showed that around one-third of all family members had similar symptoms and sleep problems.
Circadian rhythm disorder interferes with our natural sleep and wake cycle, giving sleepers a hard time falling asleep and excessive daytime fatigue. Lately, circadian genes such as ARNTL1, CLOCK, NPAS2, and PER3 have been connected to bipolar disorders. But those together with parasomnias are still to be proven and examined.
Can Sleep Disorders Cause Vision Loss?
This question is a tricky one, but it has been proven that some disorders such as obstructive sleep apnea can hinder your vision abilities and lead to a total loss of vision. Sleepers with sleep apnea experience breathing stops multiple times during the night, due to that the oxygen level varies highly over the night, and those high oscillations in oxygen level usually impact our eyes and vision. Some of the vision problems that may come as an outcome are glaucoma, floppy eyelid syndrome, central serous retinopathy, and retinal vein occlusion.
Some studies have tried to link sleep deprivation with vision problems as well as excessive sleeping and sleep quality. The progress in this area of research can be meaningful especially for seniors who are most liable to problems with vision.
The Mysteries of Dreams
One of the most fascinating sleep mysteries is dreams, since the beginning of the time people were mesmerized with them, wrote dream books and tried to explain their meaning, but even today scientists cannot fully understand why do we dream, and what is happening while we are dreaming.
We all have dreams almost every night, and those vivid scenes sometimes can be related to the things that we experienced, or we were thinking about them. On the other hand, some dreams are completely irrational, confusing, and we cannot relate them to anything from our everyday life. Because they are so hard to explain, they are liable to superstitions and many questionable interpretations. Dream books are popular even today, and in them, all sorts of dreams have been interpreted and attached to some meaning or a message since people tend to believe that dreams are transferring some sings to us, or showing us the way we should go.
Scientific studies of dreams are called oneirology, and these studies are trying to find a connection between dreams and brain function. Around 60 years ago, sleep researcher Eugene Aserinsky was performing an overnight sleep study on his son, and he accidentally noticed rapid eye movements during sleep. Those eye movements were then connected to higher brain activity which annulled the long supported idea that the sleep is a passive condition. In another, pioneering paper from 1957. Nathaniel Kleitman and William Dement researched the connection between dream content and rapid eye movements. They woke up their participants during the REM stage and asked them to describe their dreams, and then they tried to connect those interpretations to the kind of eye movements (horizontal, vertical or mixed). The ones who have vertical eye movements reported scenes such as climbing a ladder and standing at the bottom of a cliff. The participant with horizontal movements described a scene in which people were throwing tomatoes on each other, while those with mixed eye movements were dreaming people that are close to them. After this pioneering study, evidence about the correlation between dreams and REM have not been consistent, but one recent study found that the patients with REM behavior disorder have coordinated eye and limb movements during the stage of REM.