You spend one third of your life doing it… but the science of sleep is still one of the biggest mysteries known to man. While boffins worldwide still struggle to explain why humans can’t survive without it – only in the past 25 years have they begun to lift the sheets on this fascinating phenomenon. Here are the top 20 discoveries made so far:
British Ministry of Defence researchers have been able to reset soldiers’ body clocks so they can go without sleep for up to 36 hrs. Tiny optical fibres embedded in special spectacles project a ring of bright white light (with a spectrum identical to a sunrise) around the edge of soldiers’ retinas, fooling them into thinking they have just woken up. The system was first used on US pilots during the bombing of Kosovo.
Humans sleep on average around three hours less than other primates like chimps, rhesus monkeys, squirrel monkeys and baboons, all of whom sleep for 10 hours. The record for the longest period without sleep is 18 days, 21 hours, 40 minutes during a rocking chair marathon.
The record holder reported hallucinations, paranoia, blurred vision, slurred speech and memory and concentration lapses.
It’s impossible to tell if someone is really awake without close medical supervision. People can take cat naps with their eyes open without even being aware of it.
Anything less than five minutes to fall asleep at night means you’re sleep deprived. The ideal is between 10 and 15 minutes, meaning you’re still tired enough to sleep deeply, but not so exhausted you feel sleepy by day.
The extra-hour of sleep received when clocks are put back has been found to coincide with a fall in the number of road accidents.
Dreams, once thought to occur only during REM (Rapid Eye Movement) sleep, also occur (but to a lesser extent) in non-REM sleep phases. It’s possible there may not be a single moment of our sleep when we are actually dreamless.
REM dreams are characterised by bizarre plots, but non-REM dreams are repetitive and thought-like, with little imagery – ie obsessively returning to a suspicion you left your mobile phone somewhere.
Elephants sleep standing up during non- REM sleep, but lie down for REM sleep.
Some scientists believe we dream to fix experiences in long-term memory, that is, we dream about things worth remembering. Others think we dream about things worth forgetting – to eliminate overlapping memories that would otherwise clog up our brains.
Dreams may not serve any purpose at all but be merely a meaningless byproduct of two evolutionary adaptations – sleep and consciousness.
Scientists have not been able to explain a 1998 study showing a bright light shone on the backs of human knees can reset the brain’s sleep-wake clock.
The “natural alarm clock” which enables some people to wake up more or less when they want to is caused by a burst of the stress hormone adrenocorticotropin. Researchers say this reflects an unconscious anticipation of the stress of waking up.
Adults during the Victorian era (according to historical diaries) show adults slept nine to 10 hours a night, with periods of rest changing with the seasons in line with sunrise and sunsets.
The 1989 Exxon Valdez oil spill off Alaska, the Challenger space shuttle disaster and the Chernobyl nuclear accident have all been attributed to human errors in which sleepdeprivation played a role.
Tiny luminous rays from a digital alarm clock can be enough to disrupt the sleep cycle even if you do not fully wake. The light turns off a “neural switch” in the brain, causing levels of a key sleep chemical to decline within minutes.
Ducks at risk of attack by predators are able to balance the need for sleep and survival, keeping one half of the brain awake while the other slips into sleep mode.
Experts say one of the biggest sleep distractions is the 24-hour accessibility of the internet.
It is suspected that a considerable amount of sleep-related behaviour, such as when and how long a person needs to sleep, is regulated by our genes. Researchers have discovered some evidence that seems to support this assumption.
A good night’s sleep triggers changes in the brain that help to improve memory. These findings might help to explain why children – infants, in particular – require much more sleep than adults. The study also suggests sleep helps in the rehabilitation of stroke patients.