By Stephanie Guzowski, published on August 31, 2007 - last reviewed on June 9, 2016
What really happens when your head hits the pillow? Sure, sleep fulfills some very basic needs—like maintaining your physical and mental health, not to mention preparing you for those crucial daytime hours. But a lot more happens after the lights go out. Did you know that sleep affects your memory, your heart, and even the health of your teeth? Here, we unveil some of sleep's strangest facts.
From a special vacation to a holiday gathering, long-term memories are predominantly formed during sleep when the brain replays recent experiences. But how do you remember what happens when? According to researchers at the University of Lubeck in Germany, shut-eye not only strengthens a memory's content but also the sequence in which they are experienced. Students were presented sets of words in a particular order. One group of these students was allowed to sleep and another was not. Those who were allowed to sleep could more often recall the order of words than those who were not allowed to sleep.
A good night's sleep is essential for a healthy ticker. Lack of sleep can lead to hypertension, a condition in which blood pressure is chronically elevated. Of course, with it comes a higher risk of heart attack or stroke. Even normal, healthy people, who are persistently deprived of proper sleep, suffer increased risk of hypertension, say researchers at the American Academy of Sleep Medicine. Ongoing sleep deprivation can set up chemical and hormonal changes in the body, including the release of stress hormones like adrenaline.
Tossing and turning can affect your smile. A Journal of Periodontology study shows that the amount of sleep you get can significantly affect your teeth. While smoking negatively impacted oral health the most, hours of sleep closely followed. The study tracked 219 Japanese factory workers from 1999 through 2003. Participants who slept seven to eight hours a night had less periodontal disease than those who slept six hours or less a night. Researchers speculate that sleep shortage impairs the body's immune system, something that can lead to bad teeth.
Want to keep Johnny slim and trim? Sleep will help. Researchers at Northwestern University found that children who get more sleep tend to have lower body mass index and are less likely to become overweight than kids who sleep less. Sleeping an additional hour a night reduced a child's chance of being overweight by about 30 to 35 percent. The link between sleep and childhood obesity is still up for grabs, but researchers have noted that tired children may very well be less active. Also lack of sleep could disrupt hormones that influence metabolism and hunger.
Sleep to Your Own Rhythm
If you find yourself awake and energetic late at night, you may have a genetic mutation. The altered gene may explain why some people prefer late nights. This gene affects the body's circadian cycle-the clock that keeps our metabolism, digestion, and sleep patterns in sync. Researchers discovered abnormally long circadian rhythms in some mice-lasting about 27 hours instead of the normal cycle of 24 hours. These mice had the mutated gene. Also, night owls who compensate by staying in bed longer still experience more insomnia than the rest of us. Also, night owls report feeling less in control of their sleep, which may also fuel insomnia.
Not all is quiet after lights-out. Sleep disorders plague many. There are those who walk, those who talk, or those who eat in their sleep. Now a study in the journal Sleep even documents those who have sex while asleep. In fact, many abnormal sexual behaviors emerge during sleep including sexual vocalizations, intercourse with or without orgasm, and masturbation. Eighty percent of sleep-sex cases involve men, with only males engaging in sleep-sexual intercourse. Women, meanwhile, were more likely to engage in sexual vocalizations. And both genders reported instances of sleep masturbation.
Some people can survive on very little sleep, while others require many hours to function normally. If you still perform relatively well when sleep deprived, the reason could be your genes. In one study from the University of Surrey, some people struggled to stay awake after two days of no sleep while others had no problem whatsoever. The researchers looked into this further and gave the participants the opportunity to sleep normally; they found that some participants spend more time in slow-wave sleep, the deepest form of shut-eye. And for them carrying a sleep debt makes it that much harder to stay alert and function.