1. There’s a part of your brain that regulates your circadian rhythms with the help of light.
It’s a bit like a master clock for your body, and it’s called the “suprachiasmatic nucleus”. It lives just above part of your brain called the optic chiasma and receives input from your eyes about the amount of light in the outside world.
2. Blind people often have trouble with sleep because daylight is so important to regulating circadian rhythms.
About half of all blind people who have no light perception at all suffer from non-24-hour sleep-wake disorder, where their internal clock doesn’t match up with the day and night cycle.
3. We tend to sleep a few minutes less per night around a full moon.
A study published this year showed that humans get less sleep, and less deep sleep, around the full moon, even if they sleep in a windowless room.
4. You burn more calories watching TV than you do sleeping.
But that is not an excuse to stay up and watch another episode of Breaking Bad.
5. You probably don’t need eight hours of continuous sleep a night.
There’s no magic amount of sleep that everyone needs.
6. Getting up in the middle of the night used to be normal.
There is evidence that until the late 17th century people used to sleep in two segments, separated by an hour or two when they’d be awake in the night.
7. People who sleep just 6.5 to 7.5 hours a night tend to live longest.
But it’s not yet clear whether people who tend to sleep more or less than that can adjust their sleep schedule and live longer as a result.
8. The amount of sleep different animals need varies wildly.
Giraffes need an average of 1.9 hours, but cats need more than 12 hours a day.
9. Some animals have to wake from hibernation to get some sleep.
Scientists don’t really know why.
10. No matter how much you try, you won’t be able to dramatically alter your internal clock.
11. If you’re not a morning person, “social jet lag” makes you feel like you’re working in the wrong time zone.
Bad news for late risers who have to get up early every day for work.
12. Half of all teenagers may be sleep deprived.
Small children are early birds, but during adolescence people tend to become later risers. Half of all teenagers may be sleep deprived, thanks in part to early school start times.
13. The record for the longest period without sleep is 11 days.
It was set by Randy Gardner in 1965. Others have claimed that they’ve gone without sleep for longer, but Guinness World Records no longer keeps records of voluntary sleep deprivation attempts due to associated health risks.
14. Dolphins can stay active for 15 days or more by sleeping only with one half of their brain at a time.
So they can stay vigilant against sharks and make sure they come up for air.
15. Ducks can also sleep with half their brain at a time.
They sleep in rows so that the outer ducks can keep an eye out for danger while the inner ducks switch their whole brain to sleep mode.
16. Humans might be one of the only species that can’t keep half of their brain awake.
The list of animals that can is pretty long.
17. When you’re sleep deprived, you can function normally most of the time.
But when you lose focus, you find it harder to get back on track.
18. Sleep-deprived people make risky decisions because they’re just too optimistic.
Sleep deprivation makes you more sensitive to positive rewards, but less to negative consequences.
19. In fact, lack of sleep is like being drunk.
A study showed that after 17–19 hours without sleep, people do similarly on performance tests to those close to the safe limit for drink driving. After being awake longer, they do even worse.
20. Sleep disruption caused by working nights is even classified as a potential cause of cancer by the World Health Organisation.
Shift work involving disruption of normal sleep routines is currently classified as an “IARC 2A carcinogen”. Studies have shown that long-term night workers have a higher risk of breast cancer than women who don’t work at night.
21. Sadly, you can’t escape sleep problems by escaping Earth.
Going to space would probably make everything a whole lot worse. Without a natural day/night cycle, astronauts’ internal clocks could start to get out of sync. On a 17-month simulated Mars mission, four out of six of the crew members had sleep problems.
22. But there’s some good news! You can catch up on lost sleep.
But there’s no shortcut to repaying your sleep debt. It’s a case of sleeping those extra hours that you missed. If you miss one hour a night for a year, that’s over two weeks you’ll have to catch up on. Better get started.
23. You strengthen memories made during the day while you sleep.
But you probably need a certain amount of continuous sleep for this to happen properly.