Sleep Facts
Sleep Facts

62 Sleep Facts That Will Change How You Go to Bed Tonight

Karin Lehnardt
By Karin Lehnardt, Senior Writer
Published December 6, 2016Updated September 5, 2019

Sleep feels passive, but what happens while you'r unconscious affects your health, safety, and lifespan more than most people realize.

  • The Shocking Truth about Human Sleep

    Humans spend a third of their life sleeping (25 years or more).

    That's nearly one-third of an average life.[10]

  • Humans can survive longer without food than they can without sleep.

    Severe sleep deprivation shuts the body down quickly.[7]

  • Modern humans sleep far less than our ancestors

    Average sleep dropped from about 9 hours to 7.5 hours after electricity.[1]

  • We cycle through sleep four to five times a night.

    Each cycle lasts about 90-110 minutes.[10]

  • Falling asleep in under five minutes is a warning sign.

    This often indicates severe sleep deprivation. Most adults are chronically sleep deprived, and many think feeling exhausted is normal.[12]

  • Modern humans sleep far less than our ancestors

    The average amount of time people sleep has dropped from nine hours in the pre-lightbulb era to seven-and-a-half hours today.[10]

  • Sleeping less than 4 hours or more than 9-10 hours raises early death risk.

    Both extremes are linked to higher mortality.[8]

  • Disturbing Sleep Facts Scientists Warn About

    Sleep deprivation has been used as a form of torture.

    It's considered onoe of the most effective methods of coercion.[8]

  • Fatigue causes more fatal singe-car crashes than alcohol.

    Drowsy driving slows reflexes, impairs judgment, and causes micro sleeps.[12]

  • Sleep-related mistakes cost billions every year

    And results in thousands of deaths.[12]

  • Lack of sleep (six hours or less) can lead to higher inflammatory proteins in the blood.

    This raises the risk of disease.[8]

  • Chronic sleep loss lowers melatonin.

    Melatonin is a hormone linked to cancer protection.[12]

  • REM sleep deprivation drastically shortens lifespan in animals

    Sometimes by more than 90%.[12]

  • Sleep Disorders Most People Don't Realize They Have

    There are at least 84 identified sleep/wake disorders.

    Many go undiagnosed for years.[10]

  • Western societies normalize abnormal sleepiness

    Western industrialized societies have such high numbers of sleep deprivation that what is abnormal sleepiness is now considered normal.[10]
    • Sleep Deprivation Fact
    Most adults suffer from chronic sleep deprivation
    Interesting Sleep Disorder Fact
    Sleepwalking usually occurs within the first third of the night during slow wave sleep (John Everett Millais / "The Somnambulist")

  • Sleepwalking is also called somnambulism, from the Greek somnus (sleep) + amb (to walk).

    Most sleepwalkers remember little, if anything, about the experience. While sleepwalking, a person can sometimes use the bathroom, eat, or even talk. Scientists postulate that adult sleepwalking has a genetic component.[8]

  • Exploding Head Syndrome feels like a loud blast

    The “exploding head syndrome” is a disorder in which when someone wakes up, they feel the sensation of an explosion going off in the head. This disorder typically occurs in the elderly. The syndrome causes anxiety, rapid heart rate, and sweating.[12]

  • REM atonia, or sleep paralysis, occurs in the typical sleeper every night to prevent people from acting out their dreams.

    Only a few muscles have the ability to move during REM sleep, such as the eye muscles, the auditory muscles, and the diaphragm for respiration.[8]
    • Random Sleep Facts
    As women age, insomnia often becomes more pronounced

  • Insomnia is almost twice as common in women as it is in men.

    Especially as they age.[12]

  • “Sexsomnia” is a type of sleep behavior that occurs when someone engages in any sexual activity, from fondling to intercourse, while asleep.

    For example, one man masturbated in his sleep so vigorously that he suffered “repeated bruising of the penis.” Sufferers of sexsomnia typically have no conscious awareness of what they’re doing.[4]

  • What happens to your brain while you sleep

    We usually spend more than two hours each night dreaming.

    We dream about 4-6 times a night, and we don't remember most of them.[12]

  • Coma and anesthesia are not true sleep.

    People who are in a coma or under anesthesia may seem to be asleep but the complex, active brainwave patterns seen in normal sleep are absent.[8]

  • Upon five minutes of waking, 50% of a dream is forgotten.

    Within 10 minutes, 90% of it is forgotten.[12]
    • Sleep, those little slices of death — how I loathe them.

    - Edgar Allan Poe

  • On the first night of sleeping in a new place, one hemisphere of our brain remains more active than the other during sleep.

    Scientists believe this "vigilant mode" allows us to respond more quickly to unfamiliar, potentially danger-signaling sounds[5]

  • The brain reorganizes information during sleep.

    During sleep, the brain “consolidates” memories and skills, meaning that the brain strengthens, reorganizes, and restructures memories during sleep.[8]

  • Animal Sleep Facts That Sound Fake

    Only one half of a dolphin’s brain goes to sleep at a time. Dolphins are capable of what is known as unihemispheric sleep, in which one hemisphere of the brain goes into a deep sleep while the other hemisphere remains awake. This allows dolphins to sleep under water without drowning. Dolphins spend approximately one third of their lives asleep.[12]

  • Giraffes sleep less than two hours a day

    .Giraffes sleep only 1.9 hours a day in five- to 10-minute sessions. Koalas, however, are the longest-sleeping mammals, sleeping up to 22 hours a day.[2][3]
    • Fun Sleep Fact
    I want to be a koala
    New Parent Sleep Fact
    An estimated 10% of parents manage to get just two-and-a-half hours continuous sleep each night

  • Sleep Facts that Affect Parents and Children

    Sleep Facts that Affect Parent and Children

    During the first two years of a baby’s life, new parents will miss six months of sleep on average.[7]

  • Millions of children suffer from sleep disorders.

    Over two million children suffer from sleep disorders, often without diagnosis.[10]

  • Violent TV worsens sleep problems in young kids

    Sleep problems in children raise long-term health risks.[12]

  • Sleep-deprived children become hyperactive

    Children don’t react the same way to sleep deprivation as adults: while adults get sleepy, children become hyperactive. In fact, a lack of sleep can result in ADHD-like symptoms in kids. Children need an average of nine to 10 hours of sleep each night.[10]

  • Strange but True Sleep Facts

    Heart disease, diabetes, and obesity all have been linked to chronic sleep loss.

    Sleep is crucial to health.[12]
  • Over 70 million Americans suffer from a sleep disorder. Of those, over 60% have a chronic disorder.[10]
  • A nineteenth-century Chinese merchant was sentenced to death for murdering his wife. Sleep deprivation was deliberately chosen as the method of execution on the grounds that it would cause the maximum amount of suffering and would serve as the greatest deterrent to other potential murderers. He eventually died on the nineteenth day, having suffered terribly.[8]
  • A person’s core body temperature drops to facilitate the onset of sleep. This means that artificial heat sources, such as electric blankets, can negatively affect a person’s quality of sleep.[8]
  • Slow-wave sleep appeared about 180 million years ago. REM sleep is believed to have appeared 50 million years later. Humans most likely developed a monophasic sleep/wake pattern in the Neolithic period (10,000 B.C.).[12]
  • Sleep is a universal characteristic of complex living organisms and has been observed in insects, mollusks, fish, amphibians, birds, and mammals.[8]
  • The phenomenon of sudden, unexplained death of adults during sleep is called SUDS. In the Philippines it is known as bangungut, which literally means “to rise and moan during sleep.”[12]
  • The word “sleep” derives from the Proto-European base *sleb, “to be weak,” and is related to “slack.” “To sleep around” was first recorded in 1928.[11]
  • The Greek writer and philosopher Alcmaeon (fifth century B.C.) proposed what is probably the first theory on the causes of sleep. He postulated that sleep occurred when the blood vessels of the brain filled with blood. The blood induced pressure on the brain, which created sleepiness. When the blood left the brain, a person would wake up.[12]
  • Patients with erectile dysfunction (ED) are twice as likely to suffer from sleep apnea.[12]
  • Aristotle (384-322 B.C.) proposed that sleep occurred as long as digestion took place. The fumes from the food were absorbed into the blood stream, which were then taken to the brain, where they induced sleepiness.[12]
  • Shakespeare made many references to sleep in his writings, and his clear descriptions of insomnia suggest that he suffered from the disorder.[12]
  • A malingerer is someone who pretends to have a sleep disorder in order to get medication or other attention.[12]
  • Fifty percent of women with children agree that sleep is the best way to recharge. This is nine percentage points higher than women without children.[9]
  • Sixty-five percent of Americans lose sleep because of stress.[9]
  • The Sandman is a mythological personification of sleep. The term developed from the “sand” that is commonly found in the corner of the eyes in the morning. According to one legend, the "sandman" would throw sand in the eyes of naughty children who wouldn’t fall asleep, causing their eyes to fall out. The sandman would then collect their eyes and feed them to his own children.[12]
  • In Greek mythology, Hypnos (Somnus in Roman mythology) was the god of sleep. Thanatos, or death, was his twin. Poppies and other sleep-inducing plants grew at the entrance of Hypnos’ cave.[12]
    • History of Sleep Fact
    Hypnos, the god of sleep with his half-brother, Thanatos, the god of death (John William / "Sleep and His Half-Brother Death")
  • Scientists postulate that exercise sets a person’s biological clock into a consistent wake/sleep pattern and that it may also boost the brain’s production of serotonin, a neurochemical that encourages sleep.[10]
  • Approximately 74% of stay-at-home moms report they have insomnia almost every night, and 39% say they are too tired for sex. Forty-four percent of working moms say they are too tired for sex.[9]
  • A snoring partner wakes his non-snoring partner an average of 20 times per night, with an average sleep loss of one hour a day.[9]
  • Studies show that 85% of police officers, 80% of regional pilots, and 48% of air-traffic controllers nod off on the job. Forty-one percent of medical workers admit they have made fatigue-related mistakes.[12]
  • Sixty-seven percent of women lose sleep during their menstrual cycle each month. This is mostly due to a rapid drop in the hormone progesterone, which has sedative-type qualities.[9]
  • Both anorexia nervosa (a disorder in which a person will eat only between 400 and 800 calories a day) and bulimia nervosa (a disorder in which a person will eat between 10,000 and 30,000 calories a day) significantly interfere with sleep.[9]
  • In general, carbs make you sleepy while protein makes you more alert.[9]
  • One in four married couples sleep in separate beds.[9]
  • Snoring can become worse after drinking alcohol. Alcohol has a direct depressant effect on the tongue and other muscles in the throat, which narrows the upper airway space.[12]
  • Nocturnal emissions, or ejaculation during sleep for men or lubrication of the vagina for females, are directly linked to REM sleep. Other species, such as rats and dogs, also experience this. Nocturnal emissions, however, have little or nothing to do with sex or erotic dreams. Their biological purpose remains a mystery.[12]
  • British soldiers were the first to use special goggles that simulated the brightness of a sunrise. The goggles helped the soldiers stay awake 36 hours without sleep.[12]
  • An estimated eight out of ten blind people have problems sleeping. Those who are completely blind have the highest rate of sleep problems.[6]
  • Sleepwalking is on the rise, in part because of increased use of sleep aids, such as Ambien.[5]
  • Among primates, only humans sleepwalk.[5]
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