Most of what we know about sleep has been discovered only in the last 25 years, but it can be said that we have caught up very quickly since then. Every day we learn more and more about sleep. Read our list of 22 of the most interesting and surprising facts about sleep that you may not know.
12% of people dream entirely in black and white
Before color television made its debut, only 15% of people dreamed in color. Now things are the other way around, and only some older people dream in black and white. If you are not convinced, you can read more (in English) here.
A giraffe needs only 1.9 hours of sleep per day, while a brown bat sleeps an average of 19.9 hours per day
Its only competitor is the African elephant, which sleeps an average of 2 hours per day. See the figures for other animals here.
The record for the longest time without sleep is 11 days
This happened in 1964 to California student Randy Gardner as part of a deliberate experiment. When he was 17, he stayed awake for 11 days and 24 minutes, breaking Tom Rounds’ previous record by 2 hours. The experiment was documented by sleep researchers at Stanford while his health was monitored continuously.
During the experiment, it was found that, although extremely harmful, sleep deprivation did not cause physical damage or impair bodily functions as much as it caused cognitive and behavioral changes, as well as mood instability. Problems with concentration and short-term memory, paranoia, and hallucinations were also among the effects of sleep deprivation. When Randy was asked why he stopped the experiment, he replied that he did not remember what he was doing or why. After the experiment ended, he made up for it with 14 hours of sleep, after which his daily life returned to normal, but he suffered from insomnia for weeks.
Dysania—the condition in which you cannot get out of bed in the morning
Most of us certainly find getting out of bed in the morning challenging, but for people suffering from dysania, it is much more difficult.
The sensation of falling while half-asleep, followed by sudden awakening, is caused by the body relaxing quickly and the brain becoming confused that you are falling—which is why it does everything it can to wake you up
No one is completely sure why it happens, but it is clear that it is not associated with deteriorating health. Still, these episodes may occur more often with increased stress, more caffeine, or physical activity close to bedtime. They happen more frequently in young people and become less common as we age.
1 in 4 married couples sleep in separate beds
While we cannot help with your partner’s snoring, we can help you sleep better according to your individual needs. When you have different preferences regarding mattress firmness, double-core mattresses are an excellent solution. Two individual cores with different firmness levels on each side are enclosed in one cover. By turning over one of the cores, you can choose to sleep on a softer surface while your partner sleeps on a firmer one.
People born blind also dream. Their experience includes emotions, sounds, and smells
What dreams are like for blind people depends on whether they were born blind or lost their sight at some point in their lives. The latter dream in color, while the former experience touch, hear sounds, or perceive smells and tastes.
Pain tolerance decreases when sleep is consistently insufficient
This study (in English) suggests that cutting sleep in half also reduces our pain tolerance, although it is not 100% certain why this happens.
Sleep experts have found a direct link between favorite sleeping positions and personality traits
For example, people who sleep in the fetal position may appear stricter, but deep down they are sensitive souls.
Humans are the only mammals that deliberately postpone sleep
Think about yourself—have you ever followed a schedule, going to bed and getting up at the same times? These consistent patterns make falling asleep and waking up significantly easier, and they also ensure that you get 7–8 hours of sleep every day.
People with higher incomes sleep significantly better
We would certainly feel more at ease with more money. But does the popular 5 a.m. club—the people who get up at 5 in the morning—get enough hours of sleep?
Cats spend two-thirds of their lives asleep
This will not surprise cat “parents.” Your mattress is also their bed. Or your computer keyboard.
We spend one-third of our lives asleep
Obviously, this also depends on a person’s age, but overall, we spend one-third of our lives asleep. To ensure good-quality sleep, it is important to choose the right mattress and pillows.
It is not unusual for deaf people to use sign language in their sleep
There are many cases in which parents of deaf children or the spouse of a deaf person observe them using sign language while asleep.
Parasomnia is a term covering abnormal movements while sleeping, such as sleepwalking or eating during sleep
There are also less innocent cases of people committing crimes during parasomnia.
It is believed that around 15% of the population sleepwalk
And the myth that you should not wake someone who is sleepwalking is not true.
Sleep deprivation can lead to death more quickly than a lack of food
Neither is good for you, but sleeplessness will cause more “damage.” We often think that if we cut our sleep by even 1 hour, we gain 1 hour of productivity and time to complete tasks. The reality, however, is that even small “doses” of consistent sleep deprivation have a major impact on our health, mood, cognitive abilities, and productivity.
Imagine starting a fast—long periods without food and short intervals in which to eat. After 7 days, you would probably feel hungry, perhaps slightly physically weak and somewhat thinner. But overall, you would be fine.
But what happens if you do not sleep for an entire week? As we saw from the experiment involving California student Randy, you would find it difficult to function.
Within 5 minutes of waking up, you forget 50% of what you dreamed
According to Freud, dreams reflect the thoughts and feelings we suppress, and upon waking, the brain wants to “get rid” of them as quickly as possible. However, the more likely theory is that when we wake up, we use much more of our brain, which is why we quickly forget our dreams.
41% of Britons sleep in the fetal position.
The study was conducted by Professor Chris Idzikowski, director of SAAS, who found that the fetal position—the “baby” position—was the dominant one, along with five other positions.
Ideally, it should take no more than 10–15 minutes to fall asleep
But if you fall asleep in less than 5 minutes, the likelihood that you are chronically sleep-deprived is high.
Sleeping on your side can aid digestion
It can also help with heartburn and reduce snoring or sleep apnea.
Fear is not the primary emotion when you have nightmares
The most common emotions are sadness, anger, confusion, disgust, frustration, or guilt.
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