Sleep for many of us is the sweet relief that pacifies and restores us after a long day of work and play. Sleep is a state of unconsciousness in which the brain is relatively more responsive to internal than external stimuli. Humans spend about one-third of their lives asleep, yet most individuals know little about sleep. Normal sleep is divided into non–rapid eye movement (NREM) and rapid eye movement (REM) sleep. Waking usually transitions into light NREM sleep.
Sleep studies are something shocking. Here are some shocking realities about sleep:
-People can take cat naps with their eyes open without even being aware of it.
– The ideal to fall asleep is between 10 and 15 minutes, meaning you're still tired enough to sleep deeply, but not so exhausted you feel sleepy by day.
– A new baby typically results in 400-750 hours lost sleep for parents in the first year.
– One of the best predictors of insomnia later in life is the progress of bad habits from having sleep disturbed by young children.
– studies showed that people getting only 6 to 7 hours of sleep every night have a longer life expectancy than those who sleep 8 hours.
– The continuous brain recordings that led to the discovery of REM (rapid eye-movement) sleep were not done until 1953, partly because the scientists involved were concerned about wasting paper.
– Dreams, once thought to occur only during REM sleep, also occur in non-REM sleep phases. It's possible there may not be a single moment of our sleep when we are actually dreamless.
– Elephants sleep standing up during non-REM sleep, but lie down for REM sleep.
-Both whales and dolphins literally fall half asleep. Their brain hemispheres take turns so they can continue surfacing to breathe.
-The world record for not sleeping was set by 17-year-old Randy Gardner in 1964 when he was awake for 264 hours and 12 minutes.
– No-one knows for sure if other species dream but some do have sleep cycles similar to humans.
-In 2004 more than 35 million sleeping pill prescriptions were filled in America, a number that more than doubled from the previous four years.
– Some scientists believe we dream to fix experiences in long-term memory, that is, we dream about things worth remembering. Others reckon 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.
The average person wakes up about six times per night.
– REM sleep may help developing brains mature. Premature babies have 75 per cent REM sleep, 10 per cent more than full-term bubs. Similarly, a newborn kitten puppy rat or hamster experiences only REM sleep, while a newborn guinea pig (which is much more developed at birth) has almost no REM sleep at all.
– 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.
– British Ministry of Defense researchers has been able to reset soldiers' body clocks so they can go without sleep for up to 36 hrs. Tiny optical fibers 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.
– Seventeen hours of sustained wakefulness leads to a decrease in performance equivalent to a blood alcohol-level of 0.05%.
– 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 sleep-deprivation played a role.
– Exposure to noise at night can suppress immune function even if the sleeper doesn’t wake. Unfamiliar noise, and noise during the first and last two hours of sleep, has the greatest disruptive effect on the sleep cycle.
– 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 adrenocorticotropic. Researchers say this reflects an unconscious anticipation of the stress of waking up.
– Some sleeping tablets, such as barbiturates suppress REM sleep, which can be harmful over a long period.
– In insomnia following bereavement, sleeping pills can disrupt grieving.
– 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.
– To drop off we must cool off; body temperature and the brain's sleep-wake cycle are closely linked. That's why hot summer nights can cause a restless sleep. The blood flow mechanism that transfers core body heat to the skin works best between 18 and 30 degrees. But later in life, the comfort zone shrinks to between 23 and 25 degrees – one reason why older people have more sleep disorders.
– A night on the grog will help you get to sleep but it will be a light slumber and you won't dream much.
– After five nights of partial sleep deprivation, three drinks will have the same effect on your body as six would when you've slept enough.
– 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.
– 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.
– Ten per cent of snorers have sleep apnea, a disorder which causes sufferers to stop breathing up to 300 times a night and significantly increases the risk of suffering a heart attack or stroke.
– Teenagers need as much sleep as small children (about 10 hrs.) while those over 65 needs the least of all (about six hours). For the average adult aged 25-55, eight hours is considered optimal
– Some studies suggest women need up to an hour's extra sleep a night compared to men, and not getting it may be one reason women are much more susceptible to depression than men.
– Feeling tired can feel normal after a short time. Those deliberately deprived of sleep for research initially noticed greatly the effects on their alertness, mood and physical performance, but the awareness dropped off after the first few days.
– Diaries from the pre-electric-light-globe Victorian era show adults slept nine to 10 hours a night with periods of rest changing with the seasons in line with sunrise and sunsets.
– Most of what we know about sleep we've learned in the past 25 years.
– As a group, 18 to 24 year-olds deprived of sleep suffer more from impaired performance than older adults.
Despite many researches about sleep facts and physiology, still the precise functions of sleep remain a mystery.