Sleep

Sleep is a behavioral state that is a natural part of every individual’s life. We spend about one-third of our lives asleep. Nonetheless, people generally know little about the importance of this essential activity. Sleep is not just something to fill time when a person is inactive. Sleep is a required activity, not an option. Even though the precise functions of sleep remain a mystery, sleep is important for normal motor and cognitive function. We all recognize and feel the need to sleep. After sleeping, we recognize changes that have occurred, as we feel rested and more alert. Sleep actually appears to be required for survival.
            Very few textbooks for high school students provide any scientific information about changes that occur in the body during sleep and how those changes affect our ability to move and think. Of course, we’ve heard that a good night’s sleep will help us perform better on a test the next day, but is this based on scientific fact, or is it just a continuing myth? The lack of information in textbooks may be due to the fact that sleep research is only recently gaining recognition. A great deal remains to be learned through scientific studies, including an answer to the key question, what is the function of sleep? Although its function remains unclear, research is providing a great deal of information about what happens in the brain and body during sleep and how the body regulates sleep.

The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the person during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats.

The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day. The timing is correct when the following two circadian markers occur after the middle of the sleep episode:

  • maximum concentration of the hormone melatonin, and
  • minimum core body temperature.

            According to sleep experts, teens need at least 8.5 – 9.25 hours of sleep each night, compared to an average of seven to nine hours each night for most adults. Their internal biological clocks also keep them awake later in the evening and keep them sleeping later in the morning. However, many schools begin classes early in the morning, when a teenager's body wants to be asleep.
            Researchers from the University of Warwick, and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also double the risk of death. Professor Francesco Cappuccio said: “Short sleep has been shown to be a risk factor for weight gain, hypertension and Type 2 diabetes sometimes leading to mortality but in contrast to the short sleep-mortality association it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status and cancer-related fatigue.” “In terms of prevention, our findings indicate that consistently sleeping around 7 hours per night is optimal for health and a sustained reduction may predispose to ill-health.”

            Students may have misconceptions about what causes us to sleep, what occurs during sleep, how our body responds to a lack of sleep, and what function(s) sleep fulfills.

  •  Sleep is time for the body in general and the brain specifically to shut down for rest.

Sleep is an active process involving specific cues for its regulation. Although there are some modest decreases in metabolic rate, there is no evidence that any major organ or regulatory system in the body shuts down during sleep.

  • Getting just one hour less sleep per night than needed will not have any effect on daytime functioning.

When daily sleep time is less than an individual needs, a “sleep debt” develops. Even relatively modest daily reductions in sleep time (for example, one hour) can accumulate across days to cause a sleep debt. If the debt becomes too great, it can lead to problem sleepiness. Although the individual may not realize his or her sleepiness, the sleep debt can have powerful effects on daytime performance, thinking, and mood.

  • The body adjusts quickly to different sleep schedules.

The biological clock that times and controls a person’s sleep/wake cycle will attempt to function according to a normal day/night schedule even when that person tries to change it. Those who work night shifts naturally feel sleepy when nighttime comes. A similar feeling that occurs during travel is known as jet lag. This conflict, set up by trying to be active during the brain’s biological nighttime, leads to a decrease in cognitive and motor skills. The biological clock can be reset, but only by appropriately timed cues and even then, by one to two hours per day at best.

  • People need less sleep as they grow older.

Older people don’t need less sleep, but they often get less sleep. That’s because the ability to sleep for long periods of time and to get into the deep, restful stages of sleep decreases with age. Many older people have more fragile sleep and are more easily disturbed by light, noise, and pain than when younger. They are also more likely to have medical conditions that contribute to sleep problems.

  • A “good night’s sleep” can cure problems with excessive daytime sleepiness.

Excessive daytime sleepiness can be associated with a sleep disorder or other medical condition. Sleep disorders, including sleep apnea (absence of breathing during sleep), insomnia, and narcolepsy, may require behavioral, pharmacological, or even surgical intervention to relieve the symptoms. Extra sleep may not eliminate daytime sleepiness that may be due to such disorders.

            The measurement of eye movement during sleep is used to divide sleep into two broad types:

  • rapid eye movement (REM) and
  • non-rapid eye movement (NREM) sleep.

Each type has a distinct set of associated physiological, neurological and psychological features.
Sleep proceeds in cycles of REM and NREM phases. In humans, this cycle is on average 90 to 110 minutes [2] Each phase may have a distinct physiological function. Drugs such as alcohol and sleeping pills can suppress certain stages of sleep. This can result in a sleep that exhibits loss of consciousness but does not fulfill its physiological functions.
NREM accounts for 75–80% of total sleep time in normal human adults. In NREM sleep, the body is active and the brain is inactive, and there is relatively little dreaming. Non-REM encompasses four stages; stages 1 and 2 are considered 'light sleep', and 3 and 4 'deep sleep'. They are differentiated solely using EEG, unlike REM sleep which is characterized by rapid eye movements and relative absence of muscle tone. There are often limb movements, and parasomnia sleep walking occurs in non-REM sleep. A cyclical alternating pattern may sometimes be observed during a stage.

Despite decades of research, knowledge of sleep's function is minimal. Several theories and axioms can be read below.

  • Restoration: Sleep affects the body in several ways. Wound healing has been shown to be affected by sleep. It’s also been demonstrated that sleep deprivation affects the immune system and metabolism. It has yet to be clearly proven that sleep affects somatic growth.
  • Anabolic/catabolic cycle: Non-REM sleep may be an anabolic state marked by physiological processes of growth and rejuvenation of the organism's immune, nervous, muscular, and skeletal systems. Wakefulness may perhaps be viewed as a cyclical, temporary, hyperactive catabolic state during which the organism acquires nourishment and procreates.
  • Ontogenesis: According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism. Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass, and an abnormal amount of neuronal cell death.

            Scientists have shown numerous ways in which sleep is related to memory. In a study working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. Memory also seems to be affected differently by certain stages of sleep such as rapid eye movement sleep (REM) and slow-wave sleep (SWS).

            An intriguing occurrence during sleep is dreaming. Although reports of dreaming are most frequent and vivid when an individual is aroused from REM sleep, dreams do occur at sleep onset and during NREM sleep as well. During an average night’s sleep, about two hours are spent dreaming, mostly during REM sleep. Although some dreams are memorable because of their extraordinary or bizarre nature, other dreams reflect realistic experiences. Despite this realism, REM dreams are usually novel experiences, like a work of fiction, instead of a replay of actual events. Pre-sleep stimuli do not seem to affect dream content. In fact, the source of the content of any given dream is unknown.

Food and Drink's Effect on Sleep

  1. Drowsiness
    • Tryptophan: Some foods contain an amino acid called tryptophan that causes sleepiness. Carbohydrates make tryptophan more available to the brain, which is why carbohydrate-heavy meals can make you drowsy when accompanied with tryptophan.
    • Melatonin: Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain by converting tryptophan into serotonin and then into melatonin, which is released at night by the pineal gland in the brain to induce and maintain sleep. Melatonin is widely used in sleep aids.
    • The "Post-Lunch Dip": Some people have a temporary drop in alertness in mid-afternoon. This is most commonly known as the post-lunch dip. A large meal can make a person feel sleepy, especially if it’s rich in carbohydrates, but the post-lunch dip is mostly an effect of our biological clocks. People naturally feel tired at two different times of the day: about 2:00 AM and 2:00 PM. It is this natural drop in alertness coupled with carbohydrate and protein consumption from afternoon meals that creates the "Post-Lunch Dip".
    • Alcohol: Alcohol is commonly used as a sleep aid, however, it is not a good aid for sleep because although it helps one relax and fall asleep in the short term, it often disrupts sleep throughout the night and can keep one from entering the deeper stages of sleep, which can cause one to wake up tired regardless of having spent a proper amount of time asleep.

     

  2. Stimulation
    • Caffeine:  Caffeine is a stimulant that works by slowing the action of the hormones in the brain that make us feel sleepy. A strong dose of caffeine can stimulate the mind for a short time, but can cause a crash in alertness as it wears off.
    • Energy Drinks: The stimulating effects of energy drinks comes from the primary ingredients of natural stimulants such as caffeine, sugars, and essential amino acids, and eventually will create a similar crash in alertness to caffeine.

    Sleep debt is the effect of not getting adequate sleep; a large debt would cause one to become mentally or physically fatigued. The demands of work, social activities, and the availability of 24-hour home entertainment have caused modern people to sleep less than before.
                It is not normal for a person to be sleepy at times when he or she expects to be awake. Problem sleepiness may be associated with difficulty concentrating, memory lapses, loss of energy, fatigue, lethargy, and emotional instability. The prevalence of problem sleepiness is high and has serious consequences, such as drowsy driving or workplace accidents and errors. Lifestyle factors (not getting enough sleep, having an irregular sleep schedule, and using alcohol or certain medication) and undiagnosed or untreated sleep disorders can cause problem sleepiness. Of the more than 70 known sleep disorders, the most common are obstructive sleep apnea, insomnia, narcolepsy, and restless legs syndrome. Large numbers of individuals suffering from these sleep disorders are unaware of—and have not been diagnosed or treated for—their disorder.