Everyone knows it’s important to get enough sleep, but some people don’t realise the many things that can happen when they don’t. While it’s true that, for some reason, a few people seem to get by on four or five hours of sleep, they’re isolated cases. The rest of us can push ourselves on less sleep than we need, and we’ll probably function, but we could suffer the consequences, some more severe than others.
But how much is enough sleep?
Experts don’t agree on this point, although everything suggests that a minimum of between 7 and 9 hours of sleep is needed, according to the latest Gallup study. And of course we’re talking about quality sleep, not time spent “lying” in bed.
These are some of the consequences of not sleeping at all, or sleeping too little; some tend to occur more often than others.
1. Irritability
A team of Israeli researchers looked into the many complaints of irritability and emotional instability after several nights of sleeplessness. The study found that not getting enough sleep amplifies the negative emotional response to disruptive events.
2. Headaches
Scientists still don’t know exactly why lack of sleep leads to headaches, but doctors have been noticing the connection for more than a century. Migraines can be triggered by sleepless nights, and between 36% and 58% of people with sleep apnea wake up with terrible headaches in the morning.
3. Inability to learn
Sleepiness has long been a problem among teenagers. A study of high school students found that starting school an hour later raises standardised test scores by at least 2 percentage points in maths and 1 percentage point in reading, according to research in Nature.
But it’s not just children. Short-term memory is a crucial component of learning, and lack of sleep significantly impairs adult volunteers’ ability to remember words they had been shown the previous day. In another study, researchers found that while people tend to get better at a task when they do it more than once, this doesn’t hold if they’re kept awake after the first attempt, even if they sleep again before trying it a second time.
4. Weight gain
People who don’t get enough sleep appear to have hormonal imbalances linked to increased appetite, more cravings for high-calorie foods and an inability to control their impulses. It’s true that we burn more calories when we’re awake, but not enough to cancel out the extra calories we consume when we’re exhausted.
5. Poor vision
Lack of sleep is associated with tunnel vision, double vision and dimness. The longer you stay awake, the more visual errors you make, and the more likely you are to experience outright hallucinations.
6. Heart disease
When researchers kept people awake for 88 hours, their blood pressure went up. But even those who were allowed to sleep four hours a night had a higher heart rate than those who slept eight hours a night. Levels of C-reactive protein, a marker of heart disease risk, rose in people who were totally or partially deprived of sleep.
7. Slowness
Our reaction time is seriously affected when we don’t get enough sleep. When researchers gave West Point cadets two tests that required quick decision-making, some of them were allowed to sleep during the testing period while the others weren’t. Those who had slept did better the second time; those who hadn’t slept did worse, and their reactions slowed down. A study of college athletes found similar results.
8. Infections
Prolonged sleep deprivation, and even a single sleepless night, can prevent the body’s natural defences from fighting off microorganisms. In fact, the body uses sleep to repair certain “breakdowns” in our system. So if we don’t let it, the problems can only grow.
9. Overproduction of urine
When people sleep, the body slows down its normal production of urine. That’s why most people don’t need to urinate as much at night as they do during the day. But when someone is deprived of sleep, this normal slowdown doesn’t happen, leading to what researchers call “nocturnal urine overproduction”. This condition may be linked to some children and adults wetting the bed at night, and to what’s called nocturia: the need to go to the bathroom many times during the night.
10. Distraction
Researchers have observed that tasks requiring attention are particularly sensitive to lack of sleep. If you want to stay alert and attentive, sleep is a requirement. Otherwise, you enter an unstable state that fluctuates within seconds and can’t be described as either fully awake or asleep, and your ability to pay attention becomes erratic.
11. Vaccines work less well
Vaccines work by stimulating your body to create antibodies against a specific virus. But when you don’t sleep, your immune system is compromised, and this doesn’t work as well. In a small study, 19 people were vaccinated against hepatitis A. Ten of them got eight hours of sleep the following night, while the rest stayed awake all night. Four weeks later, those who had slept had normal levels of hepatitis A antibodies almost twice as high as those who had been kept awake.
Another study found that one sleepless night had no long-term effect on immunity after a flu vaccine, concluding that the effect might be specific to certain diseases. The hepatitis A researchers wrote that sleep should be considered an essential factor in successful vaccination.
12. Impaired speech
Severe sleep deprivation could make you sound like an incompetent idiot. According to one study, volunteers kept awake for 36 hours tended to repeat words and use clichés, and spoke monotonously, slowly and indistinctly. They were unable to express themselves properly or put their thoughts into words.
See also: Time management problems
13. Colds
If you’re wondering why you’re sick all the time and seem to catch every virus going around the office, it’s probably because you’re not getting enough sleep. When a group of 153 people were exposed to the common cold, those who had slept less than seven hours over the previous two weeks were almost three times more likely to get sick than those who had slept eight hours or more.
14. Gastrointestinal problems
One in 250 Americans suffers from inflammatory bowel disease (IBD), and sleep deficits make their symptoms much worse. Regular sleep loss also makes you more likely to develop both IBD and irritable bowel syndrome, which affects 10–15% of people in the US, and patients with Crohn’s disease were twice as likely to have a relapse when they weren’t getting enough sleep.
15. Reduced sex drive
Testosterone is an important component of sex drive and desire in both women and men. Sleep raises testosterone, while staying awake lowers it. Sleep deprivation and sleep disorders are therefore associated with reduced libido and sexual dysfunction, and people with sleep apnea are particularly at risk.
16. Pain
People in pain, especially those with chronic pain, tend not to get enough sleep. That makes sense: pain can wake you up at night and make it hard to fall asleep. But researchers have recently begun to suspect that sleep deprivation may actually cause pain, or at least increase people’s sensitivity to it. One study found that after research subjects were kept awake all night, their pain threshold (the amount of painful stimulus they could bear) was lower.
17. Diabetes
Being awake when your body wants to be asleep messes with your metabolism, which in turn raises the risk of insulin resistance and type 2 diabetes. According to one study, interventions to extend sleep duration may reduce the risk of diabetes. And four large studies in adults have found a strong association (though not a cause-and-effect relationship) between regular sleep loss and the risk of developing diabetes, even after controlling for other habits that might be relevant.
18. Sloppiness
One study found that a sleepless night contributed to a 20–32% increase in the number of errors made by surgeons. People who play sports that require precision, such as shooting, sailing or cycling, also make more mistakes when they’ve been awake for long periods.
19. Cancer
Scientists are beginning to investigate the relationship between sleep and cancer, and different types of cancer behave differently. But since a disrupted circadian rhythm and reduced immunity are direct results of sleep deprivation, it’s not surprising that preliminary research seems to indicate that people who don’t get enough sleep have a higher risk of developing certain cancers, especially colon and breast cancer.
20. Memory problems
Sleep disorders in older people can lead to structural changes in the brain associated with impaired long-term memory, and sleep-related memory deficits have been observed in the adult population at large. As far back as 1924, researchers noticed that people who slept more forgot less. Not getting enough sleep has also been linked to higher levels of beta-amyloid, a biomarker of Alzheimer’s disease.
21. Genetic disruption
A 2013 study shed some light on why sleep is linked to so many different aspects of our health and well-being. Lack of sleep actually alters normal gene activity. After a week of sleeping less than six hours a night, researchers found that more than 700 genes were not behaving normally, including some that help regulate the immune response and stress.
Some genes that normally cycle according to a daily pattern stopped doing so, while others that don’t normally follow a daily pattern started to. What does this mean? Just one week of less sleep is enough to throw your gene activity out of control.
22. Unhappiness and depression
In a classic study led by psychologist and Nobel laureate Daniel Kahneman, a group of 909 working women kept detailed records of their moods and day-to-day activities. While differences in income of up to $60,000 had little effect on happiness, a bad night’s sleep was one of the two factors that could ruin the next day’s mood.
Another study found greater marital happiness among women who slept more soundly, although it’s hard to say whether happy people sleep better, better sleep makes people happier, or, most likely, a combination of the two. People with insomnia are also twice as likely to develop depression, and preliminary research suggests that treating sleep problems can successfully treat depressive symptoms.
23. Death
Many health problems are associated with lack of sleep, but here’s the big one: people who consistently don’t sleep 7–8 hours a day are more likely to die over a given period. Put more simply: we all die in the end, but sleeping too little, or even too much, is associated with a higher risk of dying sooner than expected.
That said, you can afford to lose anything, but don’t let anything rob you of your sleep.
Featured image: Michael Cory, CC BY 2.0, via Flickr.
