40 Surprising Facts You Didn't Know About Your Sleep

You diet when you want to lose weight. You network when you want to land a job. You meditate because the self-help gurus said you should.

We work so hard to make ourselves feel good. But very few of us actually try to sleep better. We should.

More and more studies prove that a good's night sleep is not a luxury, it's a necessity—and one we're not allowing ourselves. That's why we researched the 40 most interesting facts about sleep, and make sure each insight is also news you can use—to sleep better, be happier and sleep tighter, once and for all.

To prevent gravitational folds, elastic creases or crow's feet, sleep face up. Studies show sleeping on your stomach or side puts repeated pressure on your facial muscles, which leads to the breakdown of collagen. Bingo: Wrinkles.

Besides preventing wrinkles, sleeping on your back is also the healthiest way to snooze, experts say, because it allows your head, neck and spine to rest in a neutral position. That prevents neck strain and an uneven distribution of weight that can lead to back pain. It's not popular—only 8 percent of us are back sleepers—but as the nearest Millennial will tell you, the best things never are.

Recommendation: Want to explore back sleeping? Buy a pillow that's designed for it, cradling your head and neck. (Target has a highly rated model for $13; you can buy it here.) You might be so comfortable that you convert in one night.

Experts say you should be cruising to dreamland within 10 to 20 minutes of your head hitting the pillow. If you fall asleep within five minutes, you're sleep deprived; if it takes more than 15 minutes, you could be suffering from insomnia.

Recommendation: Read on for expert advice on how to combat both.

Ever had that uncomfortable feeling when you're half-asleep and suddenly you jolt awake? It's called a hypnogogic jerk, a harmless involuntary contraction of muscles. It could be accompanied by a sensation of falling. That certainly makes it uncomfortable, but it's a normal phenomenon: 70 percent of people have experienced at least one, and an unlucky 10 percent have it daily.

Recommendation: The occasional "sleep start" is nothing to worry about, but sometimes the condition is confused with restless leg syndrome. If you're experiencing discomfort in your legs and the irresistible urge to move them (which is often worse at night), talk to your doctor.

A study done at the University of Groningen in the Netherlands found that sleeping with your socks on can make it easier to reach orgasm. Researchers found that only 50 percent of female participants were able to have an orgasm; after being given socks to wear, 80 percent did. The socks created feelings of comfort and calmed the amygdala and prefrontal cortex, the areas of the brain responsible for anxiety and fear, said study author Gert Holstege, MD, PhD.

Recommendation: If you're anorgasmic, it wouldn't hurt to try a pair of socks—or more generally, investigate any feelings of anxiety you're having.

During sleep, the body heals and recharges itself, particularly the brain, which flushes away toxins to prevent the buildup of plaques. Researchers believe this process lowers the risk of Alzheimer's and improves memory. A study published in The Journal of Neuroscience found that people who were taught specific finger movements (like hitting piano keys) were better able to recall them after 12 hours of rest. "When you're asleep, it seems as though you are shifting memory to more efficient storage regions within the brain," said study author Matthew Walker, Ph.D., of the BIDMC's Sleep and Neuroimaging Laboratory.

Recommendation: Aim for seven to nine hours of restful, quality sleep each night.

The after-lunch slump is no myth, so you can stop guilting yourself about going crazy at the pizza buffet (although you probably should step away from the pizza buffet): Scientists have determined that tiredness peaks at 2pm and 2am. "Human beings are biphasic (physically designed for two sleeps a day), with two major bodily rhythms (homeostatic sleep drive and circadian arousal) which pull us in different directions in terms of staying awake or sleeping, but they fascinatingly align in the middle of the day to create a 'nap zone,'" said Dr. Fiona Kerr, a neuroscientist at the University of Adelaide.

Recommendation: If you're lucky enough to be able to take a midday nap, let nature knock you out. Just don't sleep longer than 15 or 20 minutes—any more can make you drowsy after you wake. (Read on for the scientifically determined perfect nap duration.)

According to the Centers for Disease Control and Prevention, being awake for 18 hours is the same as having a blood-alcohol level of 0.05 percent. (The legal limit in most states is 0.08 percent.)

Recommendation: The CDC warns that drowsy driving can be as dangerous as drunk driving, and echoes experts who say adults should get at least seven hours nightly. Adolescents should get eight.

On a scale of 1 to 10, the ideal nap is a 26—26 minutes long, that is. For years, experts advised that a short snooze of 20 to 30 minutes was optimal. Researchers at NASA recently pinpointed the ideal length, finding that pilots who slept in the cockpit for 26 minutes showed alertness improvement of up to 54 percent and job performance improvement by 34 percent, compared to pilots who didn't nap. "Napping leads to improvements in mood, alertness and performance such as reaction time, attention, and memory," said Kimberly Cote, PhD, professor of psychology and neuroscience at Brock University. "Longer naps will allow you to enter deeper sleep, which will contribute to the grogginess—also called sleep inertia—experienced upon awakening and disrupt nighttime sleep."

Recommendation: If you're old school, set your alarm for 26 minutes, or try a napping app that's targeted to that time, like NAP26.

If you're finding it especially difficult to part with your pillow in the morning, you could have a condition called dysania. According to the Cleveland Clinic, it can be caused by a nutritional deficiency, depression or other issues.

Recommendation: There's a difference between drowsiness and dysania: If you regularly can't get out of bed for one or two hours after you wake up, talk to your doctor about it.

Having trouble sleeping becomes increasingly common with age, but don't take it lying down (or pacing the floor). According to the National Sleep Foundation, adults need seven to nine hours of sleep a night for optimum health. In older adults, insomnia isn't nature's way of telling us we need less sleep; it's often due to some other medical condition or discomfort that can be treated.

Recommendation: If you're having difficulty getting to sleep or staying asleep, talk to your doctor.

Carrying around extra poundage? Poor sleep may be to blame. During sleep, our bodies release a hormone called leptin, which tells us we're full; at the same time, a hormone called ghrelin (a.k.a. "the hunger hormone") is reduced. When we are sleep deprived, those hormones go out of whack—leptin declines and ghrelin rises, which can lead to overeating.

Recommendation: Eat a diet full of protein, healthy fats and fiber, to prevent hunger pangs. A site like eatthis.com has food solutions that can help.

Hate to break it to you, but you can, in fact, sleep too much. Multiple studies show that regularly getting more than nine hours of sleep increases your risk of dementia. Research published in the journal Neurology found that risk to be nearly double.

Recommendation: Scientists believe an inability to get out of bed is a symptom, not a cause, of neurological conditions like dementia. If you find you're sleeping more than nine hours on a regular basis, talk to your doctor.

Zzzut alors! In France, people sleep an average of 8.83 hours each day, the most in the developed world. (Maybe it's all the cheese, which is packed with sleep-inducing tryptophan.)

Recommendation: If you can't expatriate, get your regular seven to nine hours right where you are. Remember that sleep isn't a waste of time; it's crucial to your health and longevity.

Do you snore? Do you have to listen to it? You're not alone—37 million Americans are affected by snoring on a regular basis, the National Sleep Foundation says. Your penchant for sawing logs could be the sign of a serious condition called sleep apnea, a breathing disorder that raises the risk of cardiovascular disease.

Recommendation: If you're a regular snorer, see your doctor about it.

Here's another reason to feel better about canceling those plans and staying in with Netflix: "Social jet lag" is what researchers call the pretty common phenomenon of going to bed later and sleeping in more on the weekends, and it's been connected to some scary health effects. According to a study conducted by the American Academy of Sleep Medicine, each hour of social jet lag correlates to an 11 percent increased risk of heart disease.

Recommendation: "Sleep regularity, beyond sleep duration alone, plays a significant role in our health," said study author Sierra Forbush, a research assistant in the Sleep and Health Research Program at the University of Arizona. "This suggests that a regular sleep schedule may be an effective, relatively simple, and inexpensive preventative treatment for heart disease as well as many other health problems."

Forty-seven percent of us sleep on our sides, in the fetal position. Unfortunately, according to the Cleveland Clinic, this is the Big Mac, the Whopper, the Bloomin' Onion of sleep health—pick your metaphor for misbehavior. Sleeping on your side, while tucking the chin down, sets the neck forward in a potentially painful posture, says Andrew Bang, DC, of the Center for Integrative Medicine.

Recommendation: It's best for your body to sleep on your back. But if you keep rolling back into the side-sleeping habit, adopt this position: "When you're standing with ideal posture looking at the horizon, your ear hole should line up with your shoulders," advises Bang. "Try to keep that posture when you sleep."

Sleeping face-down requires turning your head to the side, creating an unnatural neck twist and pressure. "While this is good for easing snoring, it's bad for practically everything else," says the National Sleep Foundation. "It can lead to back and neck pain, since it's hard to keep your spine in a neutral position. Plus, stomach sleepers put pressure on their muscles and joints, possibly leading to numbness, tingling, aches, and irritated nerves."

Recommendation: "It's best to try to choose another position, but if you must sleep on your stomach, try lying facedown to keep upper airways open—instead of with your head turned to one side—with your forehead propped up on a pillow to allow room to breathe," the NSF advises.

"The Starfish" is the least common sleep position—on your back, hands above your turned head, legs spread—with only 6 percent of adults reporting that they repose this way. Good thing: It can be conducive to snoring.

According to the Cleveland Clinic, today 75 percent of people report dreaming in color, while 12 percent of people report dreaming in black-and-white. Why? Here's a hint: Before the advent of color TV, only 15 percent of us dreamed in color.

Experts say we spend about three-quarters of each night in NREM (non-rapid-eye-movement) sleep. That's dreamless sleep, a lighter stage of sleep that increases as we age. Scientists aren't sure why. They do know that the remainder of our sleep, REM sleep, is when dreaming occurs.

According to the Better Sleep Council, Millennials and Gen Xers are most likely to report sleeping in the "freefall" pose — on the stomach, with legs and arms outstretched — than baby boomers.

Recommendation: If you know a Millennial, check in; make sure they're doing OK. And suggest they start sleeping on their back.

Frequent violent nightmares could be a sign of RBD (REM sleep behavior disorder), which has been associated to neurological conditions. Researchers have found that 80 percent of RBD patients go on to develop neurological conditions such as Parkinson's Disease and dementia. "For some reason, the cells in the REM sleep area are the first to be sickened, and then the neurodegenerative disease spreads up into the brain and affects the other areas that cause disorders like Parkinson's disease," said John Peever, PhD, a neuroscientist at the University of Toronto who led the research. "REM behavior disorder is, in fact, the best-known predictor of the onset of Parkinson's disease."

Recommendation: If you're experiencing frequent violent nightmares, talk to your doctor.

People who have insomnia and other sleep problems seem to have an increased sensitivity to pain, according to a study published in the journal Pain. In January, researchers at the University of California-Berkeley affirmed that research and published a possible explanation in the Journal of Neuroscience: Losing sleep seems to reduce dopamine in an area of the brain dedicated to pain response. "Sleep loss not only amplifies the pain-sensing regions in the brain, but blocks the natural analgesia centers, too," said study senior author Matthew Walker, a UC Berkeley professor of neuroscience and psychology.

Listening to music can slow your heart rate and breathing, lower your blood pressure and relax your muscles, all processes that can help you fall asleep. A study published in the Journal of Advanced Nursing found that people who listened to 45 minutes of classical music before bed reported better sleep quality than those who didn't.

Recommendation: Choose music that averages 60 to 80 beats per minute, which you're most likely to find in classical or jazz.

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A survey of 155,000 American adults asked participants if they had exercised at all in the past month, including low-intensity activities like golfing, gardening or walking. Those who had were one-third less likely to have sleep problems, and half as likely to experience daytime tiredness.

Recommendation: Remember that getting some exercise is almost always better than getting no exercise at all.

As we get older, our internal "body clock" shifts, making us tired earlier in the evening and wake up earlier in the morning. This can mislead us into thinking that we need less sleep. It isn't true—seven to nine hours are necessary for good health.

Recommendation: Keep a steady sleep routine: Go to bed and wake up at the same time every day. "It's also a good idea to get outside and take a walk early in the day," advises the National Sleep Foundation. "Aerobic activity and sunlight exposure can help put the brain and body in 'awake' mode."

When you eat too soon before you hit the hay, the calorie jolt and energy boost can keep you up. So can acid reflux—lying down can make stomach acid back up into your esophagus, causing painful heartburn. (Eating late at night probably isn't great for your weight either, although the research isn't conclusive.)

Recommendation: Experts advise eating dinner at least three hours before bedtime. If you need a late-night snack, have something light like rice cereal, bananas and milk, which Eat This, Not That! says is the perfect bedtime food.

Add good sleep to the host of benefits you get from regular workouts. According to the National Sleep Foundation, even a single session of moderate-intensity exercise (like walking) can help you fall asleep faster and have better sleep quality, even if you suffer from insomnia.

Recommendation: Experts recommend 150 minutes of moderate-intensity exercise, or 75 minutes of high-intensity exercise (such as running or swimming) each week to maintain heart health, ward off cancer and improve your sleep.

"Sleep-deprived people have higher blood levels of stress hormones and substances that indicate inflammation, a key player in cardiovascular disease," says Dr. Susan Redline, a professor of sleep medicine at Harvard Medical School. "Even a single night of insufficient sleep can perturb your system."

Recommendation: Make sure your anti-inflammatory Mediterranean diet includes plenty of Z's.

"People who don't sleep enough are at higher risk for cardiovascular disease and coronary heart disease—regardless of age, weight, smoking and exercise habits," says the National Sleep Foundation. Scientists aren't entirely sure why, but it's believed that not getting enough rest impairs body processes such as glucose (sugar) metabolism, raises blood pressure and increases inflammation. All three have been associated with cardiovascular disease.

Recommendation: To lower your risk of heart disease, follow a sensible diet, get regular exercise, don't smoke — and consider getting seven hours of sleep just as important.

It's no coincidence that levels of Type 2 diabetes have skyrocketed in the U.S. while our average sleep time has declined. Although obesity is a major risk factor, "Several lines of evidence indicate that chronic lack of sleep may contribute to the risk of type 2 diabetes mellitus," said authors of a study published in the Cleveland Clinic Journal of Medicine. "Adults are sleeping less and less in our society. Yet sleep is no longer thought of as strictly a restorative process for the body. The importance of sleep for metabolic function and specifically glucose homeostasis is now widely accepted."

Recommendation: "Adequate sleep and good sleep hygiene should be included among the goals of a healthy lifestyle, especially for patients with diabetes," say the researchers. "We urge clinicians to recommend at least 7 hours of uninterrupted sleep per night as part of a healthy lifestyle.

Based on interviews with more than 4,000 parents, a new study printed in the journal Sleep found that parents of newborn babies face up to six years of sleep deprivation — 40 minutes per night for women, and 13 minutes nightly for men, in the first year after a baby's birth alone.

Recommendation: "Sleep deprivation can be physically and emotionally draining. Try not to worry about non-essential jobs around the house and accept help from family and friends when it's offered," says Cathy Finlay of the UK's National Childbirth Trust. If you're the parent, don't hesitate to ask for help. If you know new parents, don't hesitate to offer it.

Sorry, it's not possible to catch up on sleep. A January study published in the journal Current Biology echoed previous conclusions that extra weekend rest can't compensate for sleep lost during the week. "The benefits of weekend recovery sleep are transient," said researchers. What's more: Losing even one hour a night can land you in "sleep debt," putting your health at risk.

Recommendation: Don't make a full night's sleep a weekend thing. Get seven to nine hours nightly.

Sleep-deprived people are more likely to feel lonely and less social than people who are well rested, according to a study published in the journal Nature Communications. Researchers at the University of California-Berkeley also found that people who haven't slept enough may appear more socially unattractive to others, increasing their feelings of social isolation. "It's perhaps no coincidence that the past few decades have seen a marked increase in loneliness and an equally dramatic decrease in sleep duration," says lead study author Eti Ben Simon. "Without sufficient sleep we become a social turn-off, and loneliness soon kicks in."

Recommendation: Rethink sleep as a social activity. "Just one night of good sleep makes you feel more outgoing and socially confident, and furthermore, will attract others to you," says Matthew Walker, professor of psychology and neuroscience at UC-Berkeley and author of Why We Sleep.

Insomnia and sleep problems are a classic symptom of depression, which particularly affects men and women in middle age. It can be part of a vicious cycle—not getting enough rest and worsen depression, and vice versa.

Recommendation: If you're experiencing sleep trouble, don't just pop sleeping pills (see another reason why at No. 38) — talk to your doctor about your emotional state as well.

"If you're sleep deprived, it can decrease your ability to fight infection," says Rachel Salas, MD, an associate professor of neurology at Johns Hopkins Medicine. Here's why: During sleep, the immune system releases proteins called cytokines, which help fight infections and inflammation and ease stress. Sleep deprivation means fewer protective cytokines are produced, along with other infection-quashing antibodies and cells.

Studies have linked the use of hypnotic (sleep-inducing) drugs with an increased risk of cancer and death by any cause. Researchers aren't sure why that may be, but why risk it?

Recommendation: There are many strategies you can follow before requesting a prescription, including meditation, relaxation and avoiding screens. Talk to your doctor.

Your pillow should be washed every six months and replaced every year or two, says the National Sleep Foundation. The reason to wash: Dust mites. They can worsen allergies and asthma, impairing your breathing and worsening your sleep. The reason to replace: Feathers go flat, and foam degrades with age. Over half of us experience neck pain as we get older, which could be alleviated by purchasing a pillow that properly cradles your head and neck.

Recommendation: Both down and foam pillows can be washed in a regular washing machine. Put them in a separate load and make sure they dry completely so they don't develop mold. Throw some tennis balls or dryer balls in the dryer to help.

According to a study by the Mayo Clinic Sleep Disorders Center, 53 percent of people who sleep with their pets have disturbed rest and abnormal sleep patterns, either because of the pet's movement or the space they occupy in bed.

Recommendation: It might be time for Fluffy to get a room (or at least a bedside basket) of his own. For more ways to live your happiest and healthiest life, don't miss these essential 50 Unhealthiest Habits on the Planet.