Your Body After a Night of Not-Enough Sleep

Ah, sleep. You remember it, right? It’s what you’re supposed to be doing when you’re lying in bed checking Facebook on your phone or watching back-to-back episodes of House Hunters International.

Sleep deprivation is so common and pervasive these days that it’s now considered a public health epidemic, according to the Centers for Disease Control and Prevention (CDC). But how much sleep is enough? Researchers now have an answer: The American Academy of Sleep Medicine and the Sleep Research Society gathered a panel of 15 experts in sleep medicine and research and concluded that seven hours is the magic number when it comes to the minimum amount of sleep adults need to stay healthy.

The problem is, nearly 30 percent of adults are sleeping less than six hours per night, according to the CDC. But what exactly happens to your body when you get less than six hours of shut-eye? Is it that bad? In a word, yes.

(Infographic: Erik Mace for Yahoo Health)

Your mental capacities

“One of the most important things we have to remember is that sleep is a function of the brain,” Shalini Paruthi, MD, associate professor in the department of internal medicine and pediatrics at Saint Louis University, and spokesperson for the American Academy of Sleep Medicine, tells Yahoo Health. When you don’t get enough, the mental effects are immediate. They range from having a harder time concentrating and making decisions to having headaches and struggling to remember things, which can impact your life both personally (forgetting a friend’s birthday) and professionally (blanking mid-presentation in front of your boss).

Your ability to react quickly also slows down when you’re exhausted — which results in making mistakes. “We first lose our speed, and then we lose the accuracy,” notes Paruthi. “There are multiple studies that show being deprived — even if it’s four hours of sleep — can make someone have the same reaction time as someone who is driving under the influence. Driving while sleep-deprived is the equivalent of driving drunk.”

Your mood

And let’s not forget about mood. “Your ability to regulate and control your emotions, as well as [cope] with change, are affected,” she says. That’s a nice way of saying that you’re more likely to be grouchy and irritable when you’re short on sleep. Research shows that getting less than five hours of sleep at night can make you feel more stressed, sad, and angry.

Your heart

One study involving 3,000 adults over the age of 45 found that those who slept under six hours each night were nearly twice as likely to have a stroke or heart attack compared to adults who logged six to eight hours per night, according to the National Sleep Foundation. They were also 1.6 times more likely to have congestive heart failure. Another small study conducted by Mayo Clinic researchers found that not getting enough shut-eye significantly raises blood pressure at night.

Your blood sugar levels

Blood sugar levels are affected too. In one study, healthy men who were restricted to four hours of sleep six nights in a row showed impaired glucose tolerance — a prediabetic condition.

Your immune system

Anyone who has ever gotten a cold shortly after pulling an all-nighter knows that sleepless nights can also weaken your immune system. A recent study found that people who slumber for six hours or less at night are four times more likely to catch a cold when exposed to the virus, compared to those who sleep more than seven hours each night. “People who are sleep deprived may not be able to mount the same type of immune response as someone fully replete on their sleep,” says Paruthi.

Related: The Bad Habit That Makes You 4 Times More Likely to Catch a Cold

Your metabolism

Missing out on sleep may also be the reason your skinny jeans are feeling a little tighter these days. Being just shy of two hours of your usual amount sleep at night can slow down your metabolism. And other research shows it can rev up your appetite: A study published in the Journal of Sleep Research found that just one night of not getting enough sleep raises ghrelin levels — the hormone that signals hunger to the brain.

Your appearance

A lack of shut-eye also affects your appearance. There’s a reason they call it beauty sleep: A 2013 study in the appropriately named journal Sleep found that people rated photos of sleep-deprived adults as looking less than their best — with redder eyes, darker under-eye circles, and more fine lines and wrinkles — compared to photos of the same adults when they were well-rested. The study participants even went on to say that the adults in the photos looked sadder when they were sleep-deprived, than after a good night’s sleep.

Your love life

As if that weren’t enough, sleep deprivation can even mess with your relationship. Couples have a harder time resolving conflicts and have more frequent and serious fights when they don’t get enough sleep, according to a 2013 study published in the journal Social Psychological and Personality Science.

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