Bragging about how little sleep you require is no longer a thing. Thanks to evolving sleep science and the constant background hum of just how important sleep is, all those I-only-need-four-hours-badasses have to prove they’re cool another way. It shouldn’t be a newsflash that regular sleep—like eating and breathing—is essential for the body and brain to function properly and that bad things will happen if you are deprived of it.

Sleep deprivation can cause a broad variety of medical conditions, spanning from memory loss to hypertension and heart disease to hardcore hallucinations. Along with stress levels and caloric intake, the number of hours you sleep will directly affect your mental and physical health, say researchers. Doctors, sleep foundations, and government health organizations say that to stay healthy and perform at their peak, adults should get 7 to 9 hours of sleep per night. “We need it for a lot of biological and physiological reasons, and psychological, too,” says licensed psychologist and sleep specialist Dr. Julie Kolzet, Ph.D. “When I help my patients fix their sleep, their anxiety and depression get better.”

How Does Sleep Make Us Function Better?

Approximately a third of our lives is spent sleeping. Although the mechanics of sleep may differ among animals, most of them share our need for sleep—even insects and more simple-brained creatures. While no one is really sure of the biological reason for sleep, despite decades of research, most scientists agree that sleep is critical for physiological and mental health. Some researchers hypothesize that sleep allows the brain to shut down in order to process memories; others suggest that sleep helps regulate the body’s hormones. What we do know is that sleep deprivation adversely affects organs such as the brain, heart, and lungs as well as one’s metabolism, immune function, and tendency toward obesity.

What Happens When You Don’t Get Enough Sleep?

Within just 24 hours of staying awake, your brain will behave as if you had a blood alcohol level of .10 (that’s above the legal limit) and your memory, ability to concentrate, hand to eye coordination, attention, and hearing will all be impaired.

At 36 hours of no sleep, your chances of cardiovascular disease, high blood pressure, and hormonal imbalances will be increased.

At 48 hours of sleep deprivation, you will be susceptible to microsleeps, which are involuntary mini blackouts that can last between 2 to 30 seconds.

And at 72 hours, you will likely full-on hallucinate. Simple conversation will be beyond you.

What’s Happening To Your Brain While You Sleep?

While you’re asl, your body may be at rest, but your brain remains is at work. A small number of brain cells are responsible for keeping us asleep. One part of the hypothalamus is responsible for shutting down the brain’s arousal signals (and other areas of the hypothalamus and brain stem promote wakefulness). During sleep, your temperature and blood pressure drop. A full sleep cycle has four stages (some sleep researchers say that it’s five stages, but we’re going to go with the four theory) that you cycle through every 90 to 110 minutes.

So, in one full night’s sleep, you’ll go through these cycles several times. Before we get into the stages, here’s a quick refresher on types of sleep. There are two basic types of sleep: REM (or rapid eye movement) sleep and non-REM sleep (which has three different stages).  Also, you don’t cycle through these stages in sequence. In fact, most of the time is spent in stage 2. (Scientists can tell which stage you’re in based on the specific brain waves and neuronal activity.)

Sleep Stages

Stage 1, typically 1 to 7 minutes, is a non-REM stage that represents the transition from wakefulness to light sleep. During this time (usually several minutes), your breathing, eye movements, and heartbeat slow down and your muscles relax. Your brain waves slow down, too.

Stage 2 is the next stage of non-REM sleep, a period of about 10 to 25 minutes before you enter deeper sleep. Your body relaxes further, your eye movements stop, and your body temperature drops. Though your brain waves slow also, this stage is marked by brief bursts of electrical activity. (You know, like when you have a twitch or leg jerk.) Stage 2 is where you spend the most time.

Stage 3, which is typically 20 to 40 minutes, is the final non-REM sleep stage, characterized by the deep sleep you need to feel that you’ve had a good night’s sleep. It’s considered the peak of growth hormone release in the body, important to cell reproduction and repair, and it occurs in longer periods during the first half of the night. Your heartbeat and breathing slow considerably. At this stage, your brain waves become even slower and it may be difficult to awaken you.

Stage 4 is considered REM sleep, during this time your eyes move rapidly from side to side behind closed eyelids. Brain wave activity grows closer to activity in waking hours. Your breathing grows faster and irregular, and your heart rate and blood pressure increase close to waking levels. Although some dreaming can occur in non-REM sleep, this stage marks the time during which dreams seem to be more vivid and emotional. During REM sleep, your arm and leg muscles become temporarily paralyzed, which some scientists think prevents you from acting out your dreams. As you age, you spend less of your time in REM sleep.

What’s The Link Between Chronic Illness and Insomnia?

Chronic illness can cause disruptions in sleep patterns. Depression, heart disease, bodily pain, and memory problems are all associated with insomnia. Other conditions such as obesity, arthritis, diabetes, lung diseases, stroke, and osteoporosis were associated with sleep-related problems such as breathing pauses, snoring, daytime sleepiness, restless legs or insufficient sleep, meaning six hours or less.

What About Dreams? Why Do We Have Them?

We may not remember our dreams, but according to scientists, we dream about three to six times a night. (Ninety-five percent of them is forgotten once you wake up.) There are several views on the function of dreams. Some experts believe that the dream state is psychological and performs as a kind of psychotherapy or a response to intense emotions without evolutionary function.

There is a sizable contingent of psychologists who believe in the Freudian interpretation, which is that dreams reveal hidden truths. Some researchers hypothesize that dreaming is one way the brain processes daily information. Still others believe dreaming is physiological in response to random neuron activity. These varying interpretations are theories, however—there is no scientific conclusion about the role that dreams play and how they affect our lives.

According to Deirdre Barrett, an assistant professor in the Department of Psychiatry at Harvard Medical School, in a podcast published by the American Psychological Association, “dreaming is our brain thinking in a different biochemical state.” The benefit of dreaming is that if you are stuck in an everyday rational mindset, dreams may show you a new way to think. However, Barrett adds, “I think our waking mind gives us better advice than our dreaming mind. The dream is a great supplement.”

What Are The Most Common Sleep Disorders?

There are a number of sleep disorders, including:

  • Insomnia, a condition in which you have trouble falling or staying asleep.
  • Sleep apnea, which occurs when your breathing is repeatedly interrupted during sleep.
  • Circadian rhythm disorder, which stems from and affects the timing of sleep-wake states. It can occur with jet lag, shift work, and irregular sleep-wake rhythm.
  • Restless legs syndrome, which causes discomfort in your legs, resulting in an urge to move them, typically occurring at night.
  • Narcolepsy, a state in which you experience overwhelming daytime drowsiness and sudden, uncontrollable attacks of sleep.

How Much Sleep Do We Really Need At Different Life Stages?

As we grow, our sleep demands change. Here’s what The National Sleep Foundation recommends by age.

  • Newborns: 14 to 17 hours
  • Infants: 12 to 15 hours
  • Toddlers: 11 to 14 hours
  • Preschoolers: 10 to 13 hours
  • School-age children: 9 to 11 hours
  • Teenagers: 9 to 11 hours
  • Adults: 7 to 9 hours
  • The 65+ group: 7 to 8 hours.

The Secret To A Good Night’s Sleep

“Some people are night owls, others are early birds,” says Dr. Kolzet. “Most people are in the middle.” There’s growing research that supports that your mom was right about getting to bed early. The good news is you can change your body’s natural circadian rhythm with light boxes, sunlight, or melatonin. “Young people are more flexible in altering their biological clock,” she says.

There are plenty of ways to get a good night’s sleep. Going to bed and waking up at the same time every day is probably the most important. Another trick is to use the bed only for sleep and sex. “An important component of treatment is sleep compression,” Dr. Kolzet says, which means limiting the time you spend in bed. Here are five more tips:

  1. Exercise 20 to 30 minutes a day, but not too close to bedtime (a few hours give enough of a buffer).
  2. Avoid caffeine late in the day and alcoholic drinks before bed.
  3. Relax before bed–try a warm bath, reading, or another relaxing routine, but ideally one that doesn’t require screen time.
  4. Make your bedroom a sleep den. Keep lights  bright lights, sounds low, and the temperature cool (about 67 degrees).
  5. Don’t lie in bed awake.  If you can’t get to sleep, do something else, like reading, until you feel tired.
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Last Updated: Mar 31, 2020