While on the subject of lists (see my previous blog post), here’s a whole selection of facts about sleep, gleaned from a variety of internet lists, supported by further digging. I can’t remember what this research was for (I’m not sure I ever knew – it was for something Hamish was working on), but it’s been sitting in a folder on my desktop, so I thought I’d share it.
1. Most people (41%) in Britain sleep in the foetal position. Five other sleeping positions have been identified: the log, the yearner, the starfish, the soldier and the free faller.
2. The optimal time it takes to fall asleep at night is 10-15 minutes. If you go ‘out like a light’, it probably means that you are sleep deprived.
3. Humans are the only mammals that willingly delay sleep.
4. Dreams of people who are born blind involve emotion, sound and smell rather than sight.
5. Sleep deprivation will kill you more quickly than food deprivation.
6. Up to 15% of the population are sleepwalkers. It’s a fallacy that you shouldn’t wake someone who is sleepwalking.
7. The sensation, when half asleep, of falling and jerking yourself awake is called ‘hypnic jerks’.
8. Instead of talking in their sleep, deaf people have been reported by their partners as using sign language in their sleep.
9. 12% of people dream entirely in black and white. This percentage was much higher (85%) before the arrival of colour television.
10. Most healthy adults need seven to nine hours sleep per night. However, some people need as little as six hours, while others drop from peak performance unless they’ve slept ten hours.
11. According to the International Classifications of Sleep Disorders, shift workers are at increased risk of chronic conditions such as cardiovascular or gastrointestinal disease.
12. One of the primary causes of over-tiredness among Americans is self-imposed sleep deprivation.
13. Someone who is sleep-deprived is more likely to have a bigger appetite. This is because their leptin levels fall and leptin regulates appetite.
14. Good sleep has been shown to improve problem-solving skills and enhance memory performance of both children and adults.
15. In a study on basketball players, longer sleep was shown to significantly improve speed, accuracy, reaction times and mental wellbeing
16. A study monitoring the development of the common cold found that those who slept less than seven hours were almost three times more likely to develop a cold than those who slept eight hours or more.
17. Babies steal 1,055 hours from their parents. According to a study, new parents lose an average of 44 days of sleep in the first year.
18. Humans can sleep with their eyes open.
19. The strangers in your dreams aren’t strangers. The brain can’t create people, so it uses faces that are already in your memory bank.
20. You grow nearly a centimetre while sleeping, but you gradually shrink again once you’re up and about.
21. Scientists have found that sleep plays a “pruning role” in the brain. It takes all the new information you’ve acquired during the day, and sifts out what’s really worth storing on your limited neural hard drive.
22. The scientific term for things, such as sunlight or clocks, that sync human sleep patterns with the Earth’s 24-hour day is “zeitgeber” (German for “synchronizer.”) Natural light is the best-known zeitgeber.
23. There have been several experiments where someone has been isolated from any zeitgebers. Among the most famous, which began on July 16th 1962, French geologist Michel Siffre spent 60 days in a cave. When he emerged, judging his “days” by when he slept he believed it was August 20th, but it was in fact September 14th, a whole 25 days later. Scientists had thought the human sleep cycle was exactly 24 hours long. Siffre proved it was closer to 24 1/2 hours.
24. Other studies found that, deprived of sunlight and other cues, people’s sleep cycles get very eratic. One involving cave explorers Josie Laures and Antoine Senni, for instance, showed Senni sometimes nodded off for 30 hours at a time and woke up believing he had simply had a short nap.