Here’s What Happens When You Don’t Get Enough Sleep

Up to 70 million Americans are sleep-deprived. But those hours of lost sleep add up to a bigger health deficit than you may realize, says sleep medicine specialist Nancy Foldvary-Schaefer, DO, MS.

“Sleep is foundational to health and wellness,” Dr. Foldvary-Schaefer says. “We know that getting enough sleep and getting enough good sleep is necessary for cardiovascular health, metabolic health and even brain health.”

Exactly how is a lack of sleep harmful to your health? Let’s take a look at what happens to your body when you don’t get enough rest.

Why lack of sleep impacts your body

There are lots of reasons why you need sleep. It allows your body to:

• Conserve and store energy.
• Repair and recover from daily activity and injuries.
• Rest, reorganize and re-catalog your brain.

“Sleep is an active process for every organ of the body, including the brain,” Dr. Foldvary-Schaefer says. “We need sleep so we can restore nutrients, clear toxic materials and recharge for the next day.”

Even missing as little as 1.5 hours can have an impact on how you feel, causing short-term problems like:

• Lack of alertness.
• Memory problems.
• Moodiness and agitation.
• An inability or unwillingness to participate in normal daily activities.

“During periods of sleeplessness, hidden health hazards accumulate that can’t be covered up with concealer or reversed with caffeine.” Dr. Foldvary-Schaefer notes. “Everything from your cardiovascular system to your immune system feels the impact.”

The health effects of sleep deprivation

Beyond feeling groggy feeling and sleeping past your alarm, sleep deprivation affects many parts of your body and brain.

So, what exactly happens when you don’t get enough ZZZs? Let’s take a look at the many possible effects of sleep deprivation.

Fatigue and a lack of energy

If your internal batteries feel depleted by the early afternoon, that’s a clear sign of lack of sleep — and no, a late-day cup of coffee won’t cure it.

“If you wake up in the morning and you aren’t refreshed, and you feel exhausted or are yawning excessively during the day, those are all signs of insufficient sleep or another sleep disorder,” Dr. Foldvary-Schaefer states.

Sleep deprivation causes fatigue, low energy and excessive sleepiness, which can affect your ability to do things you love and simply complete day-to-day tasks.

Poor balance and coordination

If you’re stumbling through the day with fewer than seven hours of sleep, you’re likely to start literally stumbling.

A 2021 study found that sleep deprivation had a significant negative effect on gait (the way you walk), while other studies have found that a lack of sleep can affect your sense of balance. Both can put you at risk for accidents, falls and injuries.

Mood changes and mental health issues

It’s no big revelation that a night of bad sleep can make you feel irritated, emotional and short-tempered the next day. And chronic sleeplessness can quickly morph into mental health concerns.

“Mood disorders like depression and anxiety are also connected with chronic insomnia and sleep deprivation,” Dr. Foldvary-Schaefer cautions.

For example, research shows that people with insomnia are twice as likely to experience depression. It also shows that about 80% of people with depression experience insomnia.

In other words, sleeplessness can be a symptom of mental health issues, but it can also be a contributor to them, which creates a frustrating chicken-and-the-egg cycle.

Forgetfulness and neurological concerns

Wait, where did I put my keys? A lack of sleep affects your ability to remember and react, which can cause your brain to go blank on the most routine of tasks.

Deep stages of sleep are responsible for learning and memory. These include rapid eye movement (REM) sleep and deep non-REM sleep (also known as Delta sleep or slow-wave sleep, or SWS).

“When sleep is interrupted or cut short by going to bed too late or not getting eight hours in bed at night, your brain isn’t able to properly catalog its memories,” Dr. Foldvary-Schaefer explains.

She points to studies that show that students who pull all-nighters don’t do any better on their tests the next day: “Even though they’ve put in more hours, they’ve deprived themselves of the sleep that was needed to really ingrain those memories into their brains,” she says.

Sleep deprivation can also cause neurological disturbances like:

• Blurred vision.
• Memory lapse.
• Poor reaction time.

“Deep sleep allows our brains to clear the toxins that accumulate during our waking hours,” Dr. Foldvary-Schaefer explains, “so that we don’t develop neurodegenerative diseases like Alzheimer’s disease.”

Research shows that this process takes seven to eight hours (and sometimes more). In other words, if you’re losing sleep, so is your brain.

Changes in your appearance

If you’ve ever walked into the office and been told, “You look tired!” (Ugh, rude) you know what we mean: When you don’t get enough sleep, it can show on your face.

Sleep deprivation can cause:

• Dark undereye circles.
• Drooping eyelids.
• Pale skin.
• Red eyes.
• Swollen/puffy eyes.

There’s also a link between lack of sleep and an increase in the amount of cortisol in your body. Cortisol can break down collagen, the protein that keeps skin smooth, which means a lack of sleep could mean more wrinkles.

A weakened immune system

When you burn the candle at both ends, your immune system takes a hit. You may be more prone to getting sick and slower to bounce back from viruses like the cold or flu.

That’s because when you sleep, your body produces cytokines, proteins that send signals to other cells to keep your immune system functioning (which is a good thing!). But when you’re sleep-deprived, your body instead starts to make more white blood cells. This creates an imbalance that weakens your immune system over time.

“After consecutive days of not getting enough sleep, you may start to become more susceptible to certain illnesses,” Dr. Foldvary-Schaefer explains. “Plus, as lack of sleep affects your immune system’s ability to fight against illnesses, it may take you longer to recover.”

Weight gain

In the short term, even a couple of bad nights’ sleep can make you feel hungrier — especially for sweets and snacks. And chronic sleep deprivation is a risk factor for weight gain and obesity.

Why? Lack of sleep disrupts these key hormone levels in your body:

• Ghrelin signals to your brain when your stomach is empty and it’s time to eat.
• Leptin, which is released by your adipose tissue (body fat), helps your body maintain its normal weight on a long-term basis
• Cortisol is your body’s “stress hormone,” produced and released into your bloodstream by your adrenal glands.

Lack of sleep makes it harder to lose weight, too. A review of studies on sleep deprivation and weight found that people who got enough high-quality sleep were more likely to be successful in their weight loss efforts than people who were sleep deprived.

Higher stress levels

Are you stressed because you can’t sleep, or are you having trouble sleeping because you’re stressed? This is another “Which came first?” scenario with the same result: You, mega-frazzled and unable to catch that shut-eye you so desperately need.

It all comes back to cortisol, the stress hormone: Sleep deprivation may raise cortisol levels, which can contribute to weight gain, heart disease, anxiety, signs of aging and so much more.

“On the other hand,” Dr. Foldvary-Schaefer says, “a good night’s sleep naturally reduces cortisol levels.”

Greater chance of car accidents

Sure, you wouldn’t drive while drunk, but would you drive while exhausted? You shouldn’t. Sleep deprivation puts you at a higher risk for car accidents.

Driving after 20 hours without sleep is like driving with a blood alcohol content (BAC) of 0.08%, the legal limit in most U.S. states. The National Highway Traffic Safety Administration reports that drowsy driving accounts for thousands of crashes, injuries and fatalities each year.

Increased risk of cardiovascular disease

Not getting enough sleep also hurts your heart.

Sleep deprivation can lead to hypertension (aka high blood pressure). And one study found that people diagnosed with sleep deprivation have a higher risk of hypertensive heart disease, which is the result of long-term unmanaged high blood pressure.

Plus, untreated sleep apnea and other chronic sleep disorders put you at a higher risk for health conditions like arrhythmias (abnormal heart rhythm), obesity and Type 2 diabetes, which can all contribute to cardiovascular disease.

“Studies on these topics are all evolving, but there's a lot of evidence to suggest that short sleep — meaning less than seven hours on average for adults — is harmful to your health,” Dr. Foldvary-Schaefer says.

Increased risk of other health issues

Chronic sleep deprivation is associated with an increased risk of other conditions, too.

“When your body doesn’t get the restoration it needs, that leads to a buildup of toxins and inflammatory markers that we believe underlie the development of a number of chronic diseases,” Dr. Foldvary-Schaefer warns.

Not getting enough sleep raises your risk for:

• Alzheimer’s disease. “Sleep deprivation over the lifespan increases your risk of cognitive impairment and dementia,” Dr. Foldvary-Schaefer says. Studies show that adults who regularly sleep for six hours or less per night accumulate toxins in the brain that can lead to Alzheimer’s disease.
• Pre-diabetes. Sleep deprivation can lead to higher-than-normal blood sugar levels, which can ultimately turn into glucose intolerance and insulin resistance.
• Thyroid and other hormonal issues. Your body needs plenty of rest so that it can properly produce hormones via the endocrine system. Sleep deprivation can cause abnormal thyroid function and growth hormone secretion, specifically for kids and young adults.

Sleep deprivation affects kids, too

There’s good reason to teach kids healthy sleep habits from an early age: Chronic sleepiness in kids and teens has seriously dangerous effects on their development.

A lack of sleep can lead to:

• Behavior problems.
• Impaired learning.
• Poor concentration.
• Decreased school performance.

How much sleep do you need?

Unless you’ve really been making a point to get enough sleep, chances are high that you’re not getting enough. Recent studies show that at least 30% of American adults are sleeping less than seven hours per night

But most people need at least that much, according to a report from the National Sleep Foundation. It breaks down sleep recommendations into nine age-specific categories, with a slight range that allows for individual preferences:

• Adults, 65+ years: 7 to 8 hours.
• Adults, 26 to 64 years: 7 to 9 hours.
• Young adults (18 to 25 years): 7 to 9 hours.
• Teenagers (14 to 17 years): 8 to 10 hours.
• School-age children (6 to 13 years): 9 to 11 hours.
• Preschool children (3 to 5 years: 10 to 13 hours.
• Toddlers (1 to 2 years): 11 to 14 hours.
• Infants (4 to 11 months): 12 to 15 hours.
• Newborns (0 to 3 months): 14 to 17 hours.

Genetic, behavioral and environmental factors help determine how much sleep each individual needs. But Dr. Foldvary-Schaefer says a minimum of seven hours of sleep for adults is a step in the right direction to improve your health.

How to combat sleep deprivation

If you eat well and exercise regularly but don’t get at least seven hours of sleep every night, you may be undermining all of your other efforts. And we’re not being dramatic! Sleep isn’t a luxury; it’s a necessity.

“Adults need seven to eight hours of sleep each night — not just once in a while,” Dr. Foldvarey-Schaefer says. “If you’re not getting that, you’re likely chronically sleep deprived. It’s the most common cause of tiredness in our society today.”

Here’s how to start taking steps to get better sleep:

• Shift your bedtime back. Start going to bed just 15 or 20 minutes earlier. Then, after a couple of days, add another 20.
• Create a nighttime routine. Practicing “sleep hygiene” can help normalize your sleep schedule.
• Skip the nightcap. Alcohol can disrupt your sleep cycle more than you realize.
• Break your bad habits. Easier said than done, right? But it’s doable. Power down an hour before bed by turning off your tech and putting an end to “revenge bedtime procrastination.”

Tried everything and still can’t seem to wake up well-rested? It might be time to bring in the professionals.

If you snore (or suspect you do) or otherwise just can’t seem to get a good night’s sleep, make an appointment to chat with a healthcare provider. They may recommend a sleep study to rule out any sleep disorders and get to the root of the problems — so that you can finally start getting the beauty rest you reserve.