Miss a night? You'll get over it. But if you're chronically sleep-deprived, here's how your body will react. 

By Nancy Rones
Updated May 09, 2018
cat awake on bed
Credit: Westend61/Getty Images

Cheating sleep is the American way. About 35 (bleary-eyed) percent of us clock less than seven hours of sleep a night, according to the Centers for Disease Control. Turning in later always seems like a good idea at the time—you may squeak out extra time for work, exercise, or binge-watching your latest obsession—but the negative effects can way outweigh those short-term benefits. The fact is, adults need 7 to 9 hours of sleep a night, and when we don't get it, it takes a toll. Experts break down exactly what happens to your body when you don't get enough sleep on a regular basis.

Your Immune System Falters

A lack of zzz’s trips up your immune system, leaving you more vulnerable to colds and infections, including ear infections, the flu, and pneumonia, according to researchers at the University of California—San Francisco. Based on their study, people who sleep 5 hours or less a night, report overall trouble sleeping, or have previously been diagnosed with a sleep disorder are the ones most likely to reach for a tissue. “Your immune system relies on sleep to function properly, including helping to ward off and rebound from a cold or illness,” says Joyce K. Lee, MD, Director of the Sleep Center at Banner University Medical Center in Phoenix, Arizona. “While you’re fast asleep, your body is hard at work repairing cells and building up energy.”

Your Body Stockpiles Calories

If you’re skimping on sleep, you might need to stop blaming tight clothes on your dryer. Many studies connect obesity with sleep deprivation. One recent example: A 2017 British study in the journal PLOS One looked at data from over 1,600 adults and found that people who sleep about six hours a night are more likely to be overweight and have larger waistlines than those who snooze for nine hours. Experts are exploring several potential reasons for the link between weightiness and little sleep. A bad night seems to shift appetite-controlling hormones, pumping up ghrelin, which stimulates hunger. It may be no coincidence that research has shown that sleep deprivation drives people to overconsume high-fat snacks and has linked sleeping five hours or less with a higher consumption of caffeinated, sugar-sweetened drinks. P.S. Being overweight and sleep deprivation both up your risk for diabetes. Not good.

Your Memory Fails

Sleep keeps your brain tidy and organized by sweeping away toxic chemicals that build up during the day and sorting and consolidating memories. “During this process, memories are transmitted from the brain’s hippocampus to the prefrontal cortex, the part of the brain where long-term memories are stored,” says Dr. Lee-Iannotti. “In cases of severe sleep loss, memories aren’t transmitted, which causes forgetfulness.” Studies also show that chronic sleep loss increases your risk of Alzheimer’s.

Your Heart Gets Weaker

Habitually sleeping less than seven hours a night increases your risk of developing or dying from coronary heart disease, a common cause of heart attack, according to the American Heart Association. Short-changing yourself on sleep triggers low-grade inflammation and increases risk factors for poor cardiovascular health, including high blood pressure and obesity, according to a European Heart Journal study. Unfortunately, further research shows that making up your weekly sleep debt over the weekend doesn’t reverse the risk to your ticker.

Your Mind Goes Into Worry Overdrive

Yes, a lousy night’s sleep can result in a moodier version of you the next day, but your emotional state can plummet to more serious levels. When you sleep less than eight hours a night, you may have trouble brushing worrisome negative thoughts aside, according to a Binghamton University study. Getting stuck on negative thoughts, playing them over and over again in your mind, can ultimately lead to mental disorders, such as anxiety and depression.