You've heard it time and time again: Get more sleep. We all know we should, but with such busy lives — working, raising a family, tending to chores — and distractions like social media, sleep often gets pushed to the backburner.
But experts aren't telling us to get more rest for nothing. Poor sleep can have a negative effect on nearly every part of the body.
That's why the American Academy of Sleep Medicine and the Sleep Research Society recommend adults get at least seven hours of sleep per night to promote optimal health. However, according to the Centers for Disease Control and Prevention (CDC), about 35 percent of adults don't reach that minimum.
Here's how sleep (or lack thereof) affects your body, from head to toe.
Your noggin is one of the most active parts of your body during slumber.
"While you're asleep, the brain is processing information that has been obtained during the day, forming new memories, solidifying things that you've learned that are important and also tossing out some things that aren't quite as important," says Carl W. Bazil, MD, PhD, director of the epilepsy and sleep division of the Department of Neurology at Columbia University Medical Center in New York City.
That's why pulling an all-nighter before a test or presentation tends to backfire. "You're cramming all this information in, but you don't really process it and retain it," he explains.
In short, you need rest to seal in the information you've learned. In fact, a March 2012 study published in PLoS ONE showed that people who slept shortly after learning something were better able to recall the information later.
In addition, skimping on sleep can negatively affect your decision-making, problem-solving and the way you handle your emotions, according to the National Institutes of Health (NIH), which notes that sleep deficiency is also linked to depression, suicide and risky behaviors. Plus, says Meena Khan, MD, a neurologist and sleep medicine specialist at The Ohio State University Wexner Medical Center in Columbus, Ohio, lack of shut-eye can decrease both your attention span and ability to concentrate.
Read more: 8 Ways to Keep Your Brain Sharp as You Age
Missing your 40 winks can affect your peepers. In a small September 2013 study of 40 participants, published in Sleep, people who were deprived of sleep were rated as having more hanging eyelids, redder eyes, more swollen eyes and darker circles under the eyes than people who got eight hours of normal slumber.
But the effects of sleeplessness go beyond appearance. "If sleep is disturbed and the muscles around the eye aren't allowed adequate rest, then eye spasms and twitches may occur," says Anil Rama, MD, a doctor of sleep medicine at the Stanford Center for Sleep Sciences and Medicine in Palo Alto, California. While these symptoms don't affect vision, they can certainly be annoying.
More serious, obstructive sleep apnea, a condition in which breathing pauses throughout the night, can cause glaucoma and anterior ischemic optic neuropathy (an inflammation of the vessels of the eye), both of which can lead to blindness, says Dr. Rama.
"The hormone leptin suppresses hunger, and ghrelin stimulates appetite. If someone is sleep-deprived, it has been shown that leptin decreases and ghrelin increases, which could promote weight gain."
If you find yourself craving junk food after a sleepless night, blame it on your nose. According to a small study of 29 people published October 2019 in eLife, when you're tired, your nose is more attuned to high-fat, calorie-dense food. In the study, participants made healthy choices after a good night's sleep. But after getting just four hours of shut-eye another night, they reached for doughnuts, cookies and chips the next day. Through MRI scans, the researchers found that the participants' brains were actually interpreting food smells differently after being sleep-deprived.
Too little slumber could also be the culprit behind your runny nose. Why? When you're in dreamland, your body is strengthening your immune system so its infection-fighting cells and proteins can ward off foreign invaders (think colds, the flu and other illnesses).
However, insufficient sleep disrupts the functioning of the immune system, so it won't do its job as well. Indeed, a September 2015 study in Sleep found that people who snooze for less than six hours per night are more likely to get sick when exposed to a cold virus. Worse, once you're ill, a lack of shut-eye can make it tougher to recover, according to the National Sleep Foundation.
Blood pressure decreases during normal sleep. But if you're not getting enough, your blood pressure stays elevated for longer periods. This could lead to chronic hypertension, which is one of the leading risk factors for heart disease and stroke, according to the CDC.
What's more, it seems chronic lack of sleep can worsen outcomes for those with high blood pressure. In one study, researchers monitored the sleep habits of 1,654 adults and then followed up with them nearly 20 years later. Their results, published October 2019 in the Journal of the American Heart Association, showed that those with hypertension who slept less than six hours per night were twice as likely to die from heart disease or stroke.
Disrupted sleep, as seen in sleep apnea, is also problematic. "When you have those constant disruptions in breathing, you get big fluctuations in blood pressure, which are a strain on the heart and can also contribute to high blood pressure and other kinds of heart disease," says Dr. Bazil.
Lack of zzzs can negatively affect the heart indirectly, too, by leading to unhealthy eating, high stress levels and decreased motivation to exercise — all of which can contribute to heart disease, per the CDC.
Too much or too little sleep may be a bane to your breathing. One study, published December 2019 in Proceedings of the National Academy of Sciences, found that people who regularly get more than 11 hours or less than four hours of sleep at night are two to three times more likely to have pulmonary fibrosis, an incurable lung disease that makes it progressively harder to breathe.
Researchers found the link after studying UK Biobank data, which includes more than a half million people. In an effort to figure out the why behind the connection, they studied samples of human lung tissue and concluded that these less-than-ideal sleep patterns alter the production of collagen, which is a key protein in lung fibrosis.
Researchers have begun to link lack of sufficient sleep and altered sleep habits to inflammation in the gut. One study, published September 2019 in Nature, found that the brain's circadian clock has a strong affect on immune cells in the intestine responsible for healthy fat metabolism, and disrupting this clock can lead to inflammation and weight gain.
Too little sleep can also cause you to overeat. In fact, insufficient time spent snoozing can lead to an increase in snacking after dinner and weight gain, per a February 2019 study published in Current Biology.
"The hormone leptin suppresses hunger, and ghrelin stimulates appetite," says Dr. Kahn. "If someone is sleep-deprived, it has been shown that leptin decreases and ghrelin increases, which could promote weight gain."
Those hormonal changes are why you tend to be ravenous when you're short on shut-eye.
Even worse for your waistline, the lack of sleep isn't just linked to overeating — it causes you to crave specific kinds of junk foods, like cookies, candies and chips, according to the National Sleep Foundation.
In addition, your body doesn't do as good a job controlling blood sugar when you haven't gotten enough sleep. That puts you at higher risk of developing type 2 diabetes, according to the NIH.
Insufficient snoozing can also lead to stomachaches and indigestion.
"Disturbed sleep causes bodily stress, which triggers blood and nutrients to be diverted away from the gut and to other parts of the body," says Dr. Rama. "That means whatever food is in your stomach won't face the normal acid and bile secretions, the contractions by the gut to move the food along will be reduced and absorption of the food will be delayed."
The result: constipation, diarrhea, bloating, flatulence, heartburn and pain.
Beauty rest really is a thing. While you're snoozing, your skin is hard at work repairing cells that were damaged during the day. Insufficient sleep increases levels of inflammation and stress hormones, which can worsen skin problems like acne, eczema and psoriasis, according to the National Sleep Foundation.
And there's more: In the September 2013 Sleep study, the sleep-deprived people were described as having paler skin, more fine lines and wrinkles around the eyes and drooping at the corners of the mouth. In a similar study with 122 people, published in Royal Society Open Science in May 2017, people who hadn't gotten enough shut-eye for two consecutive nights were rated as less attractive.
Your sleep quality can even affect your pain perception. Sleep deprivation increases pain sensitivity by numbing the brain's painkilling response, according to a March 2019 study in the Journal of Neuroscience.
Your sleep habits can affect your other bedroom activities. In a May 2015 study in the Journal of Sexual Medicine, women who got an extra hour of sleep were more likely to have sex the next day. On the flip side, women who don't get enough sleep may experience reduced libido, says Dr. Rama.
For men, the latter is also true. A lack of sleep can decrease testosterone levels, thereby reducing sex drive. In addition, poor sleep was associated with a reduction in sperm concentration and sperm count, according to a May 2013 study in the American Journal of Epidemiology.
Your Bones and Muscles
Human growth hormone is released during deep sleep and is responsible for building, repairing and maintaining muscles and bones. Too little sleep means muscle repair and healing will be impaired.
"Disturbed sleep is linked with low bone density, fractures and reduced skeletal muscle mass," says Dr. Rama.
Indeed, a study published November 2019 in the Journal of Bone and Mineral Research that involved over 11,000 postmenopausal women found that sleeping five hours or less per night was linked to lower bone mineral density and osteoporosis.
Healthy Sleep Tips
Knowing how poor sleep can negatively affect your body doesn't make it any easier to doze off. But the following tips can help you get the zzzs you need, according to the experts.
- Keep a consistent schedule. Go to bed and get up at the same time, even on weekends.
- Establish a bedtime ritual. Take a warm bath, practice meditation, do some light stretching or whatever helps you relax. This signals to your brain that it's time to wind down for sleep.
- Improve your sleep environment. Make sure your bed, pillows and bed covers are comfortable. Keep your room between 60 and 67 degrees (the ideal temperature range for sleep, according to the National Sleep Foundation). Use a fan or sound machine to drown out noise if necessary. Keep your room dark.
- Work out. Getting in some physical activity during the day can make it easier to fall asleep at night.
- Use your bedroom for two things only: sleep and sex. Move the computer, TV, smartphone and other distractions to another room.
- Avoid things that will keep you up at night, such as naps in the afternoon, caffeine, alcohol or a heavy meal late in the day.
- Talk with your doctor or a sleep professional if you're still having problems sleeping.
Is This an Emergency?
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- Centers for Disease Control and Prevention: "Prevalence of Healthy Sleep Duration among Adults — United States, 2014"
- PLoS ONE: "Memory for Semantically Related and Unrelated Declarative Information: The Benefit of Sleep, the Cost of Wake"
- National Heart, Lung, and Blood Institute: "Sleep Deprivation and Deficiency"
- The Ohio State University Wexner Medical Center: "Meena Khan, MD"
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- Sleep: "Behaviorally Assessed Sleep and Susceptibility to the Common Cold"
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- Centers for Disease Control and Prevention: "How Does Sleep Affect Your Heart Health?"
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- Sleep.org: "The Ideal Temperature for Sleep"
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- eLife: "Olfactory connectivity mediates sleep-dependent food choices in humans"
- Journal of Bone and Mineral Research: "Short Sleep Is Associated With Low Bone Mineral Density and Osteoporosis in the Women's Health Initiative"
- Proceedings of the National Academy of Sciences: "The circadian clock protein REVERBα inhibits pulmonary fibrosis development"
- Mayo Clinic: "Pulmonary Fibrosis"