What is sleep and why is it important?

Sleep is vital to supporting brain and body health, yet many adults don’t get sufficient sleep to fully reap these benefits. The Centers for Disease Control and Prevention (CDC) reports that one-third of the US adult population does not get the recommended minimum of seven hours of sleep every night.

The brain and body require sleep to function properly. Without enough sleep, people have trouble with memory and concentration. For the body, poor sleep increases the risk of obesity, diabetes, and heart disease.

What is sleep?

People once believed that during sleep, the brain simply shut down to rest for the following day. Scientists now know that while the body may relax during sleep, the brain continues to work by performing essential housekeeping to maintain brain and body well-being. These tasks help learning and memory, improve mental and physical health, and restore depleted cells. Research has begun to reveal that sleep is a complex function that is crucial to overall health.


Why is sleep important?

Sleep allows the body to recover from its activities during the day. Heart rate and temperature fall to save energy, while cells regenerate throughout the body. Sleep releases hormones in the body to help build muscle mass, fight infections, and repair damaged cells and tissue. Sleep also affects metabolism hormones so that poor sleep can lead to obesity, diabetes, and insulin resistance.

Getting enough sleep is also necessary for memory and learning. Not only does sleep prime the brain for learning, but it also helps process new information learned through the day, as well as forms and saves memories. The brain will also connect memories during sleep, which can help with problem-solving and processing emotional moments to reduce their intensity.

Good quality sleep is vital for concentration, focus, decision-making, and mood, so inadequate sleep can affect job or school performance, driving, and relationships.

How Sleep Works – The Circadian Rhythm

The brain has a biological clock that signals when to sleep and when to wake up – this is called the circadian clock. This internal clock produces a sleep-wake cycle over roughly 24 hours – this cycle is called a circadian rhythm.

The hypothalamus is the area of the brain that holds the circadian clock. Different environmental cues can reset the clock, but the most important signal is light. During darkness, the circadian clock triggers the brain to produce the sleep hormone melatonin, which causes drowsiness. On the other hand, daylight turns off melatonin production leading to feeling awake. For this reason, night shift workers, travelers over time zones, and people with blindness can have difficulty sleeping.

How Sleep Works – The 4 Stages

The brain does not simply enter into sleep mode; in fact, there are four stages of the sleep cycle. The most basic types of sleep include rapid eye movement (REM) and non-rapid eye movement (NREM) sleep.

NREM sleep has three stages and occurs before REM sleep. Sleepers go through NREM stages 1-3 and then REM sleep, and this cycle continues 3-5 times a night. At the beginning of sleep, more time is in deep sleep and less in REM. As the night goes on, more time is in REM. Thus, it’s not unusual to wake up in the morning from a very vivid dream.

Sleep Deprivation

Fatal motor vehicle accidents per year caused by drowsy driving

Sleep is an essential body function, so the effects of sleep deprivation (too little sleep) or sleep deficiency (too little or poor-quality sleep) can significantly affect one’s health. Unfortunately, inadequate sleep is a common issue, with one out of three adults in the US reporting not getting enough sleep.

As a result, the health consequences of sleep deficiency and deprivation are serious. Poor sleep is linked to increased rates of heart disease, diabetes, obesity, depression, and high blood pressure. Injury and fatality is also a concern, with drowsy driving causing an estimated 6,000 fatal motor vehicle accidents a year, per the CDC. In the elderly, sleep deficiency can lead to falls and fractures.

These findings underscore the importance of sleep to mental and physical wellness. Not getting enough hours of sleep can endanger one’s well-being. However, poor quality sleep, interrupted sleep, not getting all of the sleep stages, or not sleeping in sync with the body’s circadian rhythm can also be detrimental to one’s health. To give the brain and body the time needed to repair, restore, heal, and process, getting the proper amount of truly restful sleep is crucial.

Sabina Hoque, MD MPH

Medically Reviewed

Sabina Hoque, MD MPH is a board-certified internal medicine physician with 10 years of clinical experience. In addition, she holds a masters in Public Health and has significant experience in teaching and biostatistics. She enjoys distilling complex medical information for audiences of varying levels of health literacy.

All content published on the HealthySleepGuide.com website is credited for informational purposes only. The information should not substitute as medical advice, diagnosis, or treatment. Always consult your doctor or qualified health professional with any questions regarding your health.