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

By Karin Lehnardt, Senior Writer—Reviewed for accuracy by the FactRetriever editorial team

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.

Humans spend a third of their life sleeping (25 years or more)
That's nearly one-third of an average life._[6]
Sleep deprivation is deadlier than skipping meals
Severe sleep deprivation shuts the body down quickly._[3]
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._[6]
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._[7]
Sleeping less than 4 hours or more than 9-10 hours raises early death risk
Both extremes are linked to higher mortality._[4]
Fatigue causes more fatal singe-car crashes than alcohol
Drowsy driving slows reflexes, impairs judgment, and causes micro sleeps._[7]
Lack of sleep (six hours or less) can lead to higher inflammatory proteins in the blood
This raises the risk of disease._[4]
Chronic sleep loss lowers melatonin
Melatonin is a hormone linked to cancer protection._[7]
Most adults are chronically sleep deprived
Western industrialized societies have such high numbers of sleep deprivation that what is abnormal sleepiness is now considered normal._[6]

Most adults suffer from chronic sleep deprivation

Sleepwalking usually occurs within the first third of the night during slow wave sleep (John Everett Millais / "The Somnambulist")

Sleepwalking can be scary
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._[4]

As women age, insomnia often becomes more pronounced

Women are more prone to insomnia
It's almost twice as common in women, and worsens as they age._[7]
Your brain works over time while you sleep
We dream about 4-6 times a night and consolidate memories, organizing information for the next day._[7]
The "vigilant mode"
Scientists believe this "vigilant mode" allows us to respond more quickly to unfamiliar, potentially danger-signaling sounds._[2]
Think you're sleeping enough?
Share this with your friends, and you'll all sleep better knowing the truth._[3]

An estimated 10% of parents manage to get just two-and-a-half hours continuous sleep each night

Parents get crushed
During the first two years of a baby’s life, new parents will miss six months of sleep on average._[3]
Millions of children suffer from sleep disorders
Over two million children suffer from sleep disorders, often without diagnosis._[6]
Kids react differently to sleep deprivation
Instead of getting sleepy, children often become hyperactive, sometimes mimicking ADHD symptoms._[6]
Heart disease, diabetes, and obesity all have been linked to chronic sleep loss
Sleep is crucial to health._[7]
Sleep disorders are shockingly common
Over 70 million Americans suffer from a sleep disorder. Of those, over 60% have a chronic disorder._[6]
Strange historical punishments
A nineteenth-century Chinese merchant died from deliberate sleep deprivation as a form of execution._[4]
Temperature matters
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._[4]
Sleep is ancient
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.)._[7]
SUDS (sudden unexplained death during sleep)
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.”_[7]
Lifestyle impacts sleep
Alcohol worsens snoring; carbs make you sleepy, protein keeps you alert._[5]
Stress is a major culprit
65% of Americans lose sleep because of stress, and hormonal changes make sleep even harder during menstruation._[5]
Couples struggle
1 in 4 married couples sleep in separate beds; snoring can cost an hour of sleep daily for partners._[5]