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Sleep Science
How much do you know about sleep? Here are some interesting facts about sleep you might not have been aware of.
11 Min Read | By Chris Thomson
Last Modified 17 September 2025
Most of what we know about sleep has only been uncovered in the last 25 years, but scientists have been making up for lost time. From the mysteries of dreams to the quirks of our bedtime habits, research is revealing more about sleep every day (sometimes things we never even dreamed of — pun intended). To celebrate, we’ve rounded up some of the most fascinating and surprising sleep facts you probably didn’t know.
Older generations do this more than younger ones. A study shows that before colour television, only 15% of people dreamt in colour.
Most adults cycle through REM several times, dreaming on and off throughout the night. Oftentimes, dreams only last minutes, and chances are, you’ll forget them by morning.
After an additional 5 minutes, up to 90% is gone. Freud thought dreams represented repressed thoughts, but it’s more likely because our brains get busy as soon as we wake. Learn more about why we forget our dreams.
So, yes, blind people do dream, they just experience them differently. The timing of blindness in a person’s life also affects how their dreams play out.
Sugar may bring vivid dreams, while greasy food can make sleep harder as your body digests. What you put in your body can affect the quality of sleep or the dreams you have. Learn more about how your diet can help you sleep.
Instead, researchers have found that it’s most often feelings of sadness, guilt and confusion.
Want to know the meaning behind your dreams? Check out our Dream Encyclopaedia.
On average, about 33% of our lives are spent in bed. Learn more about your life in numbers to know how you spend the rest of your life.
There have been reports of sign language in sleep, and it’s completely normal. Similar to talking in your sleep, sign language is naturally integrated for those who are deaf, so it can appear in their dreams, causing subtle hand and finger movements.
And for many, it actually helps them sleep better. Dr Sarah Brewer told us why this might actually be a good thing.
Professor Chris Idzikowski’s research also identified five other popular positions: log, yearner, starfish, soldier, and freefaller. For more, check out our article on the most common sleep positions and their meanings.
This is also according to Professor Idzikowski, suggesting that those who sleep in the foetal position “may appear tough but are actually sensitive souls right to their core.” Not only does it determine who you are, but your sleeping position may affect your dreams too.
Less than 5 minutes? Chances are, you’re sleep deprived.
Unlike animals, we usually choose to push bedtime later. Called revenge bedtime procrastination, we often feel like sleeping later can help us gain more control of our day.
Lying on your left side may reduce heartburn. Or, if you’re a front sleeper, hands above the pillow in the “freefall” position, may also aid digestion.
Sleepwalking can be harmless, but severe cases can be dangerous. If you find someone sleepwalking, don’t wake them; instead, gently direct them back into bed.
Yes, you heard right. On average, women need an extra 11 minutes of sleep.
Light snoring is common, but loud, frequent snoring may point to sleep apnea. For tips on how to stop, read our guide on ways to prevent snoring naturally.
A quick nap helps recharge, but can’t replace a full night’s sleep. Check out our ultimate guide to daytime napping just make sure you don’t sleep too late in the day or you’ll struggle to fall asleep later on.
Talking in your sleep is harmless, and don’t worry, you won’t spill your secrets!
The rest of the time is spent tossing, turning, or scrolling. Nearly half of us sleep less than the recommended 7-9 hours, while 3% of us survive on 4 hours or less.
Heat is now the UK’s top sleep disruptor. If this is you, read our guide on how to keep cool at night.
Learn how to calm anxiety for a better night’s rest.
Sleepless nights caused by snoring? Learn how to tune it out and get some well needed rest in our guide to how to sleep when someone is snoring.
Two-thirds say pets actually improve sleep. If this is you, read our guide to sleeping with your dog in the bed for the best tips on snuggling.
45% nap during remote workdays, with young adults leading the way.
For more, check out our full 2024 UK Sleep Survey to uncover the nation’s sleep habits.
The least amount of sleep any mammal needs. I’m sure we’d all love to be able to function on little sleep!
They beat even the laziest humans and make it number one on our list of the animals that sleep the most.
This allows them to keep swimming and come up for air periodically while asleep.
All bats tend to sleep a lot, but brown bats are known to sleep the most, especially in captivity.
This will come as no surprise to most cat owners. Every sofa is a sofa bed to them. Otherwise, they can be found on your favourite seat or keyboard.
You might think that due to their large size and great memory, they would need more rest. But they usually will take several short naps, often standing, rather than a long sleep.
They can sleep up to 20 hours a day, primarily to conserve energy needed for the hunt.
This prevents them from drifting apart and getting separated due to the water’s currents.
Bulldogs and pugs are especially prone due to their snout and jaw, causing some dogs to snore.
Just like humans, we all can struggle to sleep at night. They also experience the same side effects, such as getting clumsier and learning more slowly.
Beyond the standard 8-hour monophasic cycle, the different types of sleep cycles include biphasic, Everyman, Dymaxion, and Uberman cycles. The biphasic cycle splits sleep into a longer night-time rest and a shorter daytime nap. Everyman cycle consists of a 3.5-hour sleep at night and three 20-minute naps during the day. Dymaxion is where you take four 30-minute naps during the day, and finally, Uberman consists of six to eight 20-minute naps a day.
People would sleep for about 3 hours and have a period of wakefulness lasting 1-2 hours. This is called the watch, followed by a second sleep until dawn. Segmented sleep allowed for midnight reading, prayer, or socialising.
An anxiety-driven sleep disorder usually caused by trauma, sleep paralysis or nightmares, it can cause panic attacks and a complete avoidance of sleep.
According to Guinness World Records, Robert McDonald from California held the record for the longest time awake since 1986. He beat the 1964 record of 11 days and 25 hours, set by Randy Gardner. This record is now removed from the Guinness Book of Records due to the safety and health concerns that a lack of sleep can pose.
Linked to Chronic Fatigue Syndrome, Dysania makes mornings especially tough.
It goes beyond “just five more minutes.” While not a formal medical diagnosis, it’s different from dysania.
Including sleepwalking, sleep-driving, and in rare cases, even crime.
They’re harmless, but caffeine, anxiety, or late exercise can increase their occurrence. They’re also more frequent in young people and decrease as we get older.
Read more: Why Do We Twitch And Jerk In Our Sleep?
A condition where the thought of bad dreams causes stress.
Some studies suggest people sleep less and go to bed later before a full moon. Whereas a new moon can cause insomnia and restlessness. Read more about how the moon affects your sleep and why.
This comes from a study by academics at Bristol University, it can also help people relax and be more optimistic, even if you’re on a small income.
Before the days of alarm clocks, people were paid to tap on windows to wake others for work in old English towns.
A lot of cultures encourage and work around daytime naps, with some shops even shutting for an hour or two after lunch.
The average person burns 50 calories an hour, which is an average of 400 calories for 8 hours of sleep. This is because it’s part of your basal metabolic rate to perform basic functions such as breathing, digestion, and keeping your heart beating while asleep.
Neither are good for you, obviously, but research suggests that sleep is actually more important than food in the short term.
This study suggests that cutting a person’s sleep in half dramatically reduces pain threshold, although it’s not 100% clear why.
Staying awake for 16 hours can mirror a blood alcohol level of 0.05%. This means slower reaction times, less concentration and impaired decision making.
This includes sickness, diabetes, obesity and diseases like heart disease.
8 hours of sleep a night helps to keep the doctor away!
Hormones, stress, and mood disorders all play a role. Women also experience pregnancy insomnia and various changes during the menstrual cycle, which can all throw off their sleep schedules.
How long you’re sleeping isn’t all that matters; while it’s important, sleep quality is more crucial to helping you wake up refreshed. Fragmented sleep disrupts the most restorative stages. Learn how to recognise poor sleep quality.
A drink or two can be relaxing and induce drowsiness, but the quality of sleep you get declines after drinking. Learn more about why alcohol is bad before bed.
Being warm can actually interfere with sleep; instead, most people find that cooler temperatures help them fall asleep.
While most say that sleeping with a light on is harmless, it can actually increase the risk of awakenings. Instead, it’s best to sleep in a room that’s as dark as possible.
Ever heard the saying that you eat 8 spiders in your sleep during your life, well it’s not true. There’s no evidence that a spider crawls into your mouth at night, let alone that you swallow one.
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