Sleeping is a basic human need that has become increasingly more important from a public health perspective. Sleep is related to physical health, mental health, emotional health, and daily functioning. Unfortunately, many people of all age groups do not get the recommended amount of sleep. Inadequate sleep includes sleep deprivation, sleep deficiency, and even oversleeping. As a result, the amount people sleep each night could put them at risk for premature mortality, chronic conditions, and decreased quality of life3.

Physiology of Sleep

There are two types of sleep: rapid eye movement sleep (REM) and non-rapid eye movement sleep (non-REM).

Types of Sleep: REM sleep is when dreaming typically occurs. Non-REM sleep is also known as deep sleep or slow wave sleep. The two types of sleep occur in patterns of three to five cycles each night. The body depends on both types of sleep in the right amount and at the right time in order to function properly. The cycles of sleep are controlled by the body’s circadian rhythm that follows a twenty-four hour rhythm.

Process of Sleep: There are two processes that promote sleep. In the first process, the body follows a twenty-four hour rhythm or the circadian rhythm for sleep. Hormones are affected by this rhythm. The hormone adenosine accumulates during wakefulness to promote sleepiness. The body’s circadian clock releases another hormone, melatonin, which signals that it is time for sleep. During sleep, the body is able to break down the adenosine to promote wakefulness. The circadian clock also stimulates the release of the hormone cortisol as the sun rises to initiate wakefulness. The second process involves the circadian rhythm and environmental cues. The amount of lighting can influence when you feel alert and awake versus when you feel tired and sleepy. The amount of light the brain receives allows the body to align the body’s circadian rhythm with night and day.

Hormones & Sleep: Sleep helps to regulate the hormones that affect appetite. Ghrelin, the hormone associated with hunger, increases when one does not get enough sleep. Similarly, leptin, the hormone associated with fullness, decreases when one does not get enough sleep. Sleep also increases the secretion of certain hormones, such as growth hormone, prolactin, and luteinizing hormone. Other hormones are inhibited during sleep, including thyroid stimulating hormone and cortisol. Dysfunction in the endocrine system can hinder the body’s ability to secrete the appropriate hormones in the right amount and at the right time for good health.

Recommendations for Sleep

The Center for Disease Control and Prevention (CDC) reports that seven to nineteen percent of US adults do not get enough sleep every day. About forty percent of adults report accidentally falling asleep throughout the day at least once a month. The appropriate amount of sleep differs from person to person based on the time period/stage of life. The recommended average amount of sleep each night for adolescents is approximately nine to ten hours, and slightly less at seven to eight hours each night for adults and the elderly.

Recommendations for Sleep by Age Group

Age Recommended Amount of Sleep
Newborns 16–18 hours a day
Preschool-aged children 11-12 hours a day
School-aged children At least 10 hours a day
Teens 9-10 hours a day
Adults (including the elderly) 7-8 hours a day

Recommendations for sleep by age group NIH, Clemson University

Sleep Debt: The total amount of sleep that is lost each night by not getting the recommended amount of sleep is called sleep debt. The amount of sleep lost each night accumulates, and cannot be recovered, despite popular belief. Napping does not make-up completely for sleeping inadequately at night. Naps may provide relief from short-term consequences of inadequate sleep, such as decreased alertness and poor performance (See Consequences of Inadequate Sleep). Trying to “catch up” by sleeping more on days off from work may cause immediate relief from inadequate sleep, but ultimately this will disrupt the body’s sleep-wake cycle.

Effects & Benefits of Sleep

Sleep is important to the body for brain health, mental and emotional health, and physical health.

Sleep helps to support growth and development, and allows the brain to work properly. The brain requires time for sleep in order to prepare for the next day, to form new pathways for learning, and for recalling information. By getting an adequate amount of sleep each night one can improve learning, attention, and creative thinking.

Sleeping adequately each night allows better control over emotions and behavior. This allows for better decision making abilities and an increased ability to cope with changes. Mental health can suffer without adequate sleep and lead to depression, risky behaviors, and even suicide.

Sleep adequately allows the body to grow, heal, and repair itself. Growth and development is supported during sleep by hormones that are released during sleep, such as growth hormones. Hormones during deep sleep or non-REM sleep are released to promote repair of cells and tissues and promote muscle mass development. This development and repair occurs during sleep for children, teens, and adults. During sleep, the heart and blood vessels are repaired. Therefore, inadequate sleep and continued damage to the heart and vessels can lead to an increased risk for acute and chronic diseases, such as hypertension, diabetes, heart disease, kidney disease, and stroke. Adequate sleep is especially important in puberty and fertility. Sleep effects other physical aspects, such as proper immune functioning. Without adequate sleep, the immune system cannot protect the body from foreign or harmful substances.

Inadequate Sleep

Inadequate sleep includes sleep deprivation, sleep deficiency, and even oversleeping. Sleep deprivation is a specific condition in which someone does not sleep enough, whereas sleep deficiency is a much broader term. Sleep deficiency could include sleep deprivation, sleep out of sync of the body’s natural clock, sleep disorders, and/or sleep that is incomplete, meaning that one misses or does not get all of the different types of sleep the body needs.

While sleep deficiency can occur even if the recommended amount of sleep is achieved each night, sleeping more than eight hours each night, but never feeling well-rested could be indicative of a problem as well. Sleeping too much without feeling rested could be a sign of a sleep disorder or a health problem that should be discussed with a healthcare provider.

Signs & Symptoms of Inadequate Sleep

Signs and symptoms of sleep deficiency may differ between adults and children. Children may experience difficulties at school related to staying focused or being overly active. Sleeping at the wrong time, having poor quality sleep, or not sleeping enough can cause one to feel lethargic, inhibit productivity, and inhibit function throughout the day. Even seemingly small decreases in the recommended amount of sleep can impact one’s ability to function. One may be sleep deficient if dozing occurs when:

  • sitting and reading or watching television
  • sitting still in a public place
  • riding in a car for an hour without stopping
  • sitting and talking to someone
  • sitting quietly after lunch
  • sitting in traffic for a few minutes

Risk Factors for Inadequate Sleep

Sleep deficiency and sleep deprivation can affect any person, regardless of age, race, and ethnicity.However, some people may be more at risk for sleep deficiency based on their job, lifestyle, or other medical conditions. Some people’s work schedules may conflict with their natural circadian rhythm or their schedules may not leave many hours for sleep due to multiple jobs, deadlines, or long hours. Some lifestyle choices can make some people more at risk for sleep deficiency, such as alcohol, drug, or stimulant abuse. Some medical conditions can increase the risk for sleep deficiency, whether the condition is undiagnosed, untreated, or treated with a medication that interferes with sleep.

Sleep deficiency can occur even if one sleeps the recommended amount each night. For example, people who sleep against their natural circadian rhythm could be at risk. This could include those who work late shifts or those who may work through the night. This could also include workers whose sleep is routinely interrupted, such asemergency responders or caregivers. As a result, it is import to sleep when one’s body signals that it is ready to sleep.

Consequences of Inadequate Sleep

Inadequate sleep can cause negative effects on a person’s mental, emotional, and physical health. Sleep deficiency is also linked to poor health outcomes, environmental and workplace hazards, and negative consequences that are both short- and long-term.

Mental & Emotional Health: Some consequences of sleep deficiency can include the inability to focus, slow reactions, and difficulty learning. Inadequate sleep can lead to decreased productivity throughout the work day and a decreased ability to judge social emotions and reactions. Sleep deficiency can effect cognitive abilities that can interfere with the ability to process thoughts and emotions, work, and learn. For example, sleep deficiency may alter some parts of the brain to cause emotional and/or behavioral problems and influence risky behaviors. Sleep deficiency can cause a person to feel negative emotions, such as frustration, irritability, and worry. Some studies have linked sleep deficiency to mental health issues related to depression and even suicide.

Physical Health & Chronic Conditions: Continued sleep deficiency can result in the immune system becoming compromised. As a result, one may experience more frequent illnesses and/or experience greater difficulty in overcoming common illnesses3. Over time, sleep deficiency can lead to an increased risk for chronic conditions and increased risk for injury. Chronic conditions associated with sleep deficiency are: heart disease, hypertension, kidney disease, diabetes, stroke, obesity, and depression.

Sleep deficiency has been linked to an increased risk for chronic conditions because of the absence of the physical maintenance that occurs during sleep. During sleep, the body works to maintain physical health to continue processes, such as repairing damage to the heart and blood vessels. Without this vital repair process, the risk for chronic conditions including hypertension, heart disease, and diabetes rises. The risk for chronic conditions also increases because sleep deficiency can also lead to weight gain and obesity, which is a risk factor for a host of chronic conditions. Maintaining an adequate amount of sleep ensures the hormones that affect appetite are regulated. When one does not sleep enough, levels of ghrelin can rise and cause hunger to increase higher than if one sleeps adequately. Sleep also effects the regulation of insulin, the hormone related to blood glucose control. When one does not get enough sleep, blood glucose is not properly controlled. Uncontrolled blood glucose levels can be higher than normal and increase the risk for diabetes.

Environmental & Workplace Hazards: Injuries related to sleep deficiency can have an effect on people of all ages and can include: car accidents, accidental falls, broken bones, and human errors in manufacturing and chemical plants, aquatic accidents, and aviation accidents.

Microsleep can occur as a result of inadequate sleep. Microsleep is an uncontrollable event that can occur without awareness and consists of brief moments of sleep that occur during times when one would normally be awake. Working and daily activities can quickly become dangerous without adequate sleep.

Driving while sleep deficient can be dangerous and has similar effects as if driving while under the influence of alcohol. Approximately 100,000 car accidents can be attributed to the result of sleep deficient drivers, which contributes about 1,500 deaths each year. Sleep deficiency affects productivity and safety for workers, whether mechanics, healthcare, or students.

Sleep Disorders

Sleep disorders can increase one’s risk for sleep deficiency. Sleep disorders, such as insomnia and sleep apnea, can lead to sleep inadequacy and sleep deficiency. Since sleep disorders can lead to sleep deficiency, sleep disorders have been linked to some chronic conditions. Some of these include heart failure, heart disease, high blood pressure, obesity, diabetes, and depression.

Recommendations for Adequate & Improved Sleep

Try to avoid large or heavy meals and alcohol within a few hours before sleep. Other substances to avoid before bed include nicotine and caffeine, which are both forms of stimulants. Make sure to maintain physical activity and outdoor time every day, but avoid strenuous exercise close to time for sleep.

In order to improve sleep each night, set aside an hour before sleep for relaxation and quiet time. This time can be used for a hot bath or relaxation techniques Artificial light that can disrupt the sleep and wake cycles should be limited during this time. Artificial light that can cause a disruption in sleep include: television light, computer screen light, and even bright alarm clock light.

The use of a sleep journal where the amount of sleep, the degree of alertness, and the degree of drowsiness experienced throughout the day are all recorded can be used to speak with a healthcare professional about how to improve the amount and quality of sleep each night.

Be sure to allot yourself enough time to sleep adequately each night. Going to sleep and waking up at a consistent time each day through the week and on weekends can help improve sleep. While naps can be beneficial to provide symptomatic relief to increase alertness and performance, naps should be limited to the early afternoon and be no longer than twenty minutes. Some people’s work schedules make adequate sleep difficult, especially people who work later shifts. Some may also find it helpful to have a consistent work shift to allow time for the body’s circadian rhythm to adjust. It could be helpful for some to increase naps to allow more time for sleep, keep lights bright at work, and limit caffeine use to only the first part of the shift.

Additional Information

For additional information or if difficulty and problems with sleep continue, a primary care physician. Be sure to provide the primary care physician with as many details as possible about sleep habits and personal routines.


  1. Ferrie, Jane E. et. al. “Sleep Epidemiology- A Rapidly Growing Field.” International Journal of Epidemiology 40.6 (2013): 1431-437. National Center for Biotechnology Information. U.S. National Library of Medicine, 17 May 2013. Web. 9 Feb. 2017.
  2. “Insufficient Sleep Is a Public Health Problem.” Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 03 Sept. 2015. Web. 09 Feb. 2017.
  3. National Institute of Health. “Sleep Deprivation and Deficiency.” National Heart, Lung, and Blood Institute. U.S. Department of Health and Human Services, 22 Feb.2012. Web.
  4. “Normal Sleep.” The Physiology of Sleep: The Endocrine System and Sleep. N.p.: n.p., n.d. N. pag. National Sleep Foundation. Web. 09 Feb. 2017.
  5. “Sleep Physiology.” Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Ed. H. R. Colton and B. M. Altevogt. Washington D.C.: National Academies, 2006. N. pag. Print.

Originally published 04/16

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