This is what happens to your body when you don’t get enough sleep

You may eat healthy and exercise, but not getting enough sleep can undo these effects, which can ultimately be just as unhealthy. The effects of sleep deprivation go beyond feeling fatigued or yawning. A lack of sleep can have consequences on your physical and mental health.

According to the World Health Organisation, insufficient sleep is a global public health problem, with more than a third of adults getting less than the recommended seven to eight hours per night.

If you’re part of the sleep deprived, read on to learn what happens to your body when you don’t get enough sleep.

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When you don’t get adequate sleep – whether due to a chronic issue like sleep apnoea, lifestyle reasons like long work hours or raising young children, or bad habits like bingeing on Facebook before bed – it may take a toll on your brain’s ability to function. “MRI imaging shows lack of sleep reduces blood flow to areas of the brain that control higher-level thought processes,” says Dr Richard Shane, a behavioural sleep specialist and the founder of the Sleep Easily method. “It impairs your problem-solving abilities, slows your cognitive speed, and decreases constructive thinking skills and logical reasoning.”

Another effect of sleep deprivation is an inability to retain memories. “Insufficient sleep interferes with your ability to focus and learn efficiently, which is essential for you to remember something,” Dr Shane says. “Research shows that sleep strengthens nerve connections involved in memory, and also helps consolidate new information into memories. Insufficient sleep interferes with this.” Dr Michael J. Breus, a clinical psychologist known as “The Sleep Doctor,” explains that you need enough REM (rapid eye movement) sleep in order for your brain to solidify memories. “REM sleep is where you move information from your short-term memory to your long-term memory,” he says. “When you do not get enough sleep, you miss out on REM, and this affects memory.”

You’ve probably noticed that you wake up “on the wrong side of the bed” if you haven’t gotten enough shut-eye. “Sleep deprivation affects mood,” Breus says. “It makes you see everything in a more negative light because your emotions are far more volatile when sleep deprived.” Although it’s not known exactly why this is, Shane says it’s another way your brain doesn’t function well without sleep. “The area of your brain [frontal lobe] that’s in charge of thinking, reasoning and logic usually balances the area of your brain [amygdala] involved with emotions such as fear, anxiety, aggression and arousal,” he says. “MRI brain scans on people who have not had enough sleep show a decrease in connection between these brain centres, which increases reactivity, fear and anger.” If you keep waking up in the middle of the night, your brain could be in big trouble.

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Another mood disorder linked to lack of sleep is depression. “While the specific brain mechanisms are not known, in one major study [Sleep, 2005] people with chronic insomnia were ten times more likely to develop depression,” Shane says. Because a lack of sleep and depression are so interconnected, it can be hard to tease out which came first. Sleep experts suggest keeping a sleep diary to help your doctor diagnose you and decide the best treatment approach.

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Along with fuzzy brain function comes impaired decision making. “Sleep has been shown to increase risk-taking behaviour,” says Dr Clete Kushida, medical director of the Stanford Sleep Medicine Center. In a 2016 study of paediatric residents on 24-hour shifts, published in the journal Medical Decision Making, the doctors made riskier medical decisions if they hadn’t gotten at least an hour nap. But even if your job seems to have less potential for disaster, your performance at work may still suffer because of poor problem solving, higher risk-taking and poor management style without sleep, says Breus.

Sleep deprivation doesn’t only endanger your own health – it can affect the lives of others if you get behind the wheel. “Sleep has been shown to decrease your ability for alertness, vigilance and higher order cognitive functions such as executive/frontal-lobe functioning – for example, complex activities like driving a car,” says Dr Kushida. It can slow your reaction time as much as driving drunk, not to mention the risk of falling asleep behind the wheel.

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You may think the only effect of sleep deprivation on your body is that you’re really, really tired. When you don’t get enough sleep, every system in your body is affected, potentially causing long-term effects on your cardiovascular health, including your risk for high blood pressure, heart attack, and stroke, according to a study in the European Heart Journal. For people with the breathing issue sleep apnoea, the risk is even greater. “Different sleep states such as REM and non-REM have variable and complex impacts on heart rate, blood pressure, blood flow to heart, and breathing patterns,” says Dr Vaishal Shah, a staff physician in the Sleep Disorders Center at Cleveland Clinic. Sleep apnoea disrupts this pattern, and the result is that the cardiovascular system has to work harder. But even in people without a specific sleep disorder, lack of sleep has been linked with high blood pressure and heart problems, likely due to not getting enough time to slow down and recover from the day.

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“Sleep plays an important role in the regeneration of cells and has effects on inflammation in the body, which is important for healing and in some skin problems,” says Dr Shah. “Skin is also an important organ that helps regulate body temperature during sleep. So, darkening below the eyes, dull skin or puffy eyes can be a visible symptoms of lack of sleep.”

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If you’ve ever told your partner, “I’m just too tired tonight,” it might not just be an excuse. “Fatigue and sleepiness tends to decrease sex drive, in addition to lowering testosterone in men with sleep loss,” Dr Kushida says. Typically, testosterone levels rise when you fall asleep, peak during the first episode of REM sleep, and they remain at this level until you wake up. However, poor sleep can disrupt this hormonal process.

Furthermore, sleep apnoea in middle-aged men has also been previously associated with decreased testosterone, along with obesity and aging. However, a 2019 study in The World Journal of Men’s Health found while obstructive sleep apnoea (OSA) treatment does not reliably increase testosterone levels, OSA treatment combined with testosterone replacement therapy can improve hypogonadism – the failure of the testes to function properly – and also alleviate erectile/sexual dysfunction.