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Deadlines, side hustles, staying up all night watching goat videos, a new baby in the house, insomnia… there are lots of reasons people aren’t sleeping.

The Centers for Disease Control and Prevention estimate 7 to 19 percent of adults in the U.S. don’t sleep enough, and 50 to 70 million Americans have chronic sleep disorders.

Sleep deprivation means you don’t get enough sleep. Most adults need 7 to 9 hours per night. You may also be sleep deficient if you sleep at times that are out of sync with your natural rhythm or don’t sleep well at all.

Sleep deficiency is a serious condition that can lead to physical and mental health problems like heart disease, kidney disease, high blood pressure, diabetes, stroke, and depression. Not sleeping enough also puts you at greater risk for accidents and death.

If you spend those sleepless hours contemplating your mortality, it’s apropos. Extreme fatigue is associated with higher risk for driving accidents, other injuries, and potentially life-shortening conditions.

And for people with the rare disease fatal familial insomnia (FFI), not sleeping is one of the first signs they’re unwell.

FFI is an inherited disease caused by prions in the part of the brain that controls waking and sleeping. Prions destroy neurons in the thalamus, causing insomnia, weight loss, high or low body temperature, and dementia.

In most cases, symptoms begin in mid-life and lead to death within 12 to 18 months. Because FFI is genetic, you would almost certainly have had a family member with the condition. Spontaneous cases can happen, but are less common.

Assuming your lack of sleep is not of the fatal neurodegenerative variety (and it’s probably not), here’s what you can expect to experience the longer you stay awake.

Who hasn’t found themselves awake for 24 hours straight? It doesn’t feel good, but you get through it with vats of coffee, probably feeling hungover until you can actually get some sleep.

Fun fact:

Being awake 24 hours is equivalent to having a blood alcohol content of .10%. So that hungover feeling makes a lot of sense.

You definitely shouldn’t drive in that condition, and maybe shouldn’t trust your memories. A 2016 study of young adult men found they were more likely to recall false memories after being awake for 24 hours.

In another study, people who didn’t get enough sleep had a higher load of beta-amyloid in their brains. Beta-amyloid is a waste product that should be cleared during sleep. High concentrations are a risk factor for Alzheimer’s Disease.

Now you’ve been awake a day and a half. The technical term might be “cross-eyed tired.” In fact, you’re probably experiencing decreased oculomotor (eye movement) function, even if you don’t feel that tired.

And you’re not as eloquent as you would be after a good night’s rest. Researchers tested subjects after 36 hours of sleep deprivation and found they spoke in bursts of words between long silences and chose words that were semantically related, making communication less clear because of limited word choice. Sleep-deprived study participants spoke with flattened, monotone voices, which could come across as disinterest to listeners.

Research also indicates that after 36 hours awake, people are slower to shift attention to changes in their environment, have slower reaction times, and have a delayed orienting response (the reflex that allows us to process sudden stimuli).

If you were trying to navigate the jungle (or the urban jungle) without the ability to pay attention and react quickly to stimuli (aka danger), things could get scary pretty fast.

If you thought your reaction time and attention were impaired after 36 hours awake, just wait ‘til you’ve been awake 2 full days! Now you’re even more vulnerable to microsleeps — short periods of a few seconds when you appear to otherwise be awake, but don’t respond to your environment.

It’s believed that under extreme sleep deprivation, parts of the brain will hit snooze while other parts remain awake. Microsleep is particularly dangerous for fatigued drivers, but can make just about any task harder to perform.

In 2017, researchers found that military surgeons who performed operations for 48 hours with no sleep were found to be cognitively impaired, putting themselves and patients at risk. The study recommends surgeons be limited to 12-hour shifts, with adequate sleep every 24 hours.

There’s also evidence that after 48 hours of sleep deprivation, the immune system is suppressed, producing fewer “natural killer” cells that fight infection.

You’ve been awake 3 solid days and nights. Are coworkers giving you a wide perimeter at the office? That’s probably because you’re grumpy as hell. Studies indicate the following effects of 72 hours of sleep deprivation:

  • A group of astronauts experienced increased heart rate, negative mood, and impaired information processing.
  • In a 1984 study, six young men were deprived of sleep and their urine was collected daily. Researchers found an increase in urinary urea and decrease in glucose and urinary electrolytes, despite participants having free access to food and water. They concluded that sleep deprivation disrupts metabolism.
  • A more recent study of rats shows inhibited expression of the circadian clock gene and increased oxidative stress after 72 hours awake.
  • In another study of mice, sleep deprivation resulted in impaired locomotor activity, anxious behavior, oxidative stress, changes in mitochondrial enzyme complex activities, increased corticosterone levels, and signs of neuroinflammation.

These are the likely immediate effects of a few sleepless nights:

  • fatigue
  • irritability
  • brain fog
  • difficulty concentrating and making decisions
  • depressed mood
  • anxiety
  • lack of motivation
  • daytime sleepiness
  • increased risk of injury and accidents
  • longer reaction time
  • lack of coordination
  • forgetfulness
  • impaired immunity

If your sleepless nights are chronic, they can eventually lead to more serious problems, like hallucinations, severe mood swings, and increased risk of depression, mental illness, stroke, heart disease, and asthma attacks.

According to the Centers for Disease Control and Prevention, people who slept less than 7 hours per day were more likely to report these 10 chronic health conditions:

  • heart attack
  • coronary heart disease
  • stroke
  • asthma
  • COPD (chronic obstructive pulmonary disease)
  • cancer
  • arthritis
  • depression
  • chronic kidney disease
  • diabetes

The American Academy of Sleep Medicine recommends the following general sleep guidelines based on age:

AgeRecommended amount of sleep
Infants aged 4–12 months12–16 hours per day (including naps)
Children aged 1–2 years11–14 hours per day (including naps)
Children aged 3–5 years10–13 hours per day (including naps)
Children aged 6–12 years9–12 hours per day
Teens aged 13–18 years8–10 hours per day
Adults aged 18 years or older7–8 hours per day

Whether it’s work, family, fun, or illness keeping you awake at night, your brain and body are suffering for it. If you absolutely can’t get the sleep you need, try these coping tips:

  • 75 mg to 150 mg of caffeine can improve alertness and performance after sleep deprivation. Be aware that long-term use can lead to tolerance and withdrawal effects.
  • If you know you have to be awake later, bank some sleep now. A “prophylactic nap,” can improve performance and alertness.
  • Squeeze in a 30-minute nap during sleep deprivation to improve alertness. It’s better to limit nap time because the longer you sleep, the more difficult it will be for you to wake up afterward. We love the Power Nap App.
  • Pair caffeine with your nap for even greater benefits.
  • Stimulant medications can be prescribed by a doctor to help offset the negative effects of unavoidable sleep deprivation. Because of the potential for side effects or dependence on these medications, doctor supervision is a must.