4 Negative Side-Effects of a Bad Night’s Sleep

by Lauren Bedosky
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4 Negative Side-Effects of a Bad Night’s Sleep

Sleep is non-negotiable. We all need 7–9 hours every night for a healthy brain and body. And yet, 1 in 3 U.S. adults aren’t getting that, according to the Centers for Disease Control and Prevention.

Regularly skimping on sleep increases your risk for many chronic health conditions, including obesity, diabetes, high blood pressure, heart disease and mood disorders.

In fact, sleep is so important for your overall health, you’ll notice significant effects after just one night of tossing and turning.


Blame your circadian rhythm, an internal 24-hour clock that cycles between sleepiness and alertness at regular intervals (also known as your sleep-wake cycle), according to the National Sleep Foundation. “[Your circadian rhythms] have a hand in all of our body’s functions, from the brain down to cells,” says Sanam Hafeez, PsyD, a neuropsychologist and professor at Columbia University in New York City.

Specifically, your circadian rhythm helps your body regulate chemicals and systems — from your immune system to your metabolism — so you can be active when you need to be. “If you interrupt your body’s natural sleep-wake cycle, things snowball until you get the sleep you need, Hafeez says.

Here are just a handful of the effects you may feel after just one night of bad sleep.


Remember how hard it was to concentrate during class the day after staying up too late? Sleep is a time when memories reactivate, the connections between brain cells fortify, and information gets transferred from short-term to long-term memory. “Without a good night’s sleep, our brain doesn’t restore its energy, and this can affect the way you retain information, your concentration on single tasks and your memory,” Hafeez says.

So, expect to struggle with focus if you’re low on sleep — and be careful: “[Lack of focus] can be dangerous if you’re caring for someone, operating heavy machinery at work or driving,” Dr. Hafeez says.


Lack of sleep — and therefore, focus — can intensify stress, making you more likely to snap. Tasks or situations you can normally handle just fine (e.g., cleaning spilled coffee or getting called into a last-minute meeting) become incredibly irritating. “Your brain is exhausted, so you will have less patience for annoyances in your daily life,” Dr. Hafeez says.


Sleep may be even more important in a global pandemic: “When you’re sleep-deprived, your body stops producing necessary chemicals that signal to your immune system how to react to infections, inflammation and other conditions,” Hafeez says.

Your immune response depends on your wake time, as well as the time you spend in non-rapid eye movement (also known as ‘slow sleep’) and rapid eye movement (REM) sleep, according to research in the American Journal of Clinical and Experimental Immunology. If you don’t get enough time in these stages, you’ll compromise your body’s ability to fight off illness the next day.



“Lack of sleep can cause chaos when it comes to your hormones,” Hafeez says. Stress hormones like cortisol can increase, along with ghrelin or the ‘hunger hormone.’ The result: More stress and eating.

For example, a study in the February 2020 issue of the Journal of the American Heart Association reveals women were more likely to overdo it on sugar and unhealthy fats when sleep-deprived, which all added up to an extra 500–800 daily calories on average. One day of that may not have long-term effects. However, if you don’t prioritize good sleep, all those unhealthy calories add up over time, increasing your risk of heart disease and obesity.


First, don’t panic. “The best thing to do is nap a bit if possible, and head to bed early the next night,” Hafeez says.

If you decide to nap, try to limit yourself to 20–30 minutes. This way, you’ll score a short-term boost in alertness without interfering with your next night of sleep.

To avoid bad nights in the future, practice good sleep habits, like reducing your bright light exposure in the evening, using your bed for sleep only, avoiding heavy meals before bedtime, and practicing meditation, Hafeez says.

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About the Author

Lauren Bedosky

Lauren is a freelance fitness writer who specializes in covering running and strength training topics. She writes for a variety of national publications, including Men’s HealthRunner’s WorldSHAPE and Women’s Running. She lives in Brooklyn Park, Minnesota, with her husband and their three dogs.


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