There is an action which we do everyday but rarely care about it, and that is sleeping. Have you ever experienced sleep deprivation or lack of sleep? Have you ever felt that your memory seems to reduce after many days without sleeping? Our modern society takes more of the time we used to sleep, so lack of sleep becomes more and more common. Sleep deprivation affects all aspects of our lives negatively, especially our brain and health. It affects the ability of speech, speed and accuracy of thinking, reduces creative thinking, and limits the ability of learning and memorizing. It also causes health problems including diabetes, high blood pressure, heart disease, obesity, and the decline of immune function and life expectancy.

It is not easy to define the term “sleep” scientifically. In general, sleep is a process when the eyelids are often closed, muscles are freed, and the body is usually lying down. Sleep operates in a cyclical manner and is divided into two basic states. One state is known as rapid eye movement (REM) sleep, and another is non-rapid eye movement (NREM) sleep. A sleep circle normally starts with NREM and then REM. In the REM state, eyes move rapidly under the closed eyelids. The sleeper is slightly awake in this state, and dreaming frequently occurs at this point (“Sleep” par. 1, 2, 5).

In contrast to REM sleep, which is slightly simple and takes a short time, NREM is a long process and is divided into four stages. Each stage can take from five to fifteen minutes. The first stage is between wakefulness and sleep. The sleeper can be awaked easily, but the muscles begin to relax. The body then enters a period of light sleep, the second stage, where the breathing and heart rate start slowing. They continue to slow in the third stage, and the blood pressure and body temperature fall as well (“Sleep” par. 6). Finally, the body enters the final stage, the deepest sleep. This is when the process of repairing and renewing tissues, building bone, and strengthening the immune system is launched (Clemmitt 125). NREM sleep lasts about 70 to 90 minutes (“Sleep” par. 7). The sleeper then enters REM sleep, which may take about five to fifteen minutes. A night's sleep usually has five or six cycles of NREM and REM sleep, and each sleep cycle is about 1.5 hours long (Dijk par. 8).

Artificial light, computer, and Internet tend to extend our wakefulness time and to reduce our sleep time. The amount of Americans who get less than six hours of sleep on weekdays is up to 20 percent in 2009 (Clemmitt128). Furthermore, there are a lot of problems that relate to sleep deprivation. In fact, according to the Institutes of Medicine, insufficient sleep causes preventable medical errors, leading to 50,000 to 100,000 deaths each year and even over one million injuries. One group of doctors who suffer significantly from lack of sleep is newly graduated interns. They have to work continuous shifts of 24 to 36 hours without any breaks (“Sleep, Performance” par. 3). In addition, according to the estimates of the National Highway Traffic Safety Administration, there are about 100,000 police-reported accidents that happen each year because of fatigue. The Institute of Medicine also predicts that approximately 1 million crashes, 500,000 injuries, and 8,000 deaths each year in the U.S. are due to drowsy driving (“Sleep, Performance” par. 5). These statistics show that there is a connection between lack of sleep and brain performance. In other words, sleep deprivation affects the human brain negatively, especially its neurons, language-control area, and learning and memory area. But how?

Sleep is very necessary for a brain to continue functioning effectively. After a long period of time without sleeping, neurons may not work correctly. Certain stages of sleep help regenerate neurons within the brain cortex while some others are used for forming new neurons and creating new synaptic connections which are junctions between neurons and another neurons or muscles or gland cells (“The Effects of Sleep Deprivation” par. 1).

The temporal lobe of the cerebral cortex is located on the bottom section of the brain, and its role is to process language. For fully rested subjects, this area of the brain is very active. However, for sleep-deprived subjects who suffer long periods of time without sleeping, there is no activity within this region, and these subjects slur badly. Now, we can wonder that if there is no activity in the temporal lobe, why are sleep-deprived people still able to perform language tasks? This is because the parietal lobe that is a part of the cerebral cortex in either hemisphere of the brain lying below the crown of the head must become active to compensate for the loss of temporal lobe functioning. However, since this region is not often used for performing such tasks, it cannot perform language smoothly. Therefore, when the brain switches from the temporal lobe to the parietal lobe, some speed and accuracy is naturally lost (“The Effects of Sleep Deprivation” par. 3).

Sleep-deprived people also have difficulties thinking of imaginative words or ideas. They tend to repeat words or plagiarize. Moreover, it is hard for them to deliver a statement well or to react quickly to unpredicted rapid changes. This is because of the effect of the frontal lobe, which is located at the front of the brain. Its role is to process speech and advanced thinking (“The Effects of Sleep Deprivation” par. 5).

Because the brain controls everything in the body, there is the relationship between the brain and behavior. Different areas of the brain need to “snooze” during different stages of the sleep cycle, so we should not shorten our sleep time. In fact, if the brain does not receive a break,  it will soon begin to turn off for periods of microsleep. Without sleep, the performance of our brain decreases, and then our behavior begins to be problems or mistakes subsequently occur (“The Effects of Sleep Deprivation” par. 11).

Sleep deprivation also affects the brain in the ability of learning and memorizing. REM sleep is an important stage for learning and memory because many regions of brain were stimulated during REM sleep. A new skill can be performed perfectly until a learner receives at least eight hours of sleep. Full cycle sleep helps increase the production of proteins and decrease the amount of broken proteins. Proteins are used to regenerate the neurons within the brain. New synapses may not be able to be formed if these proteins are not present.That is why the ability of learning and remembering of sleep-deprived people is not good (“The Effects of Sleep Deprivation” par. 9).

One of the diseases that is considered to have a connection between lack of sleep and brain is Alzheimer's disease, a condition that involves memory loss (Saeypar. 10). The disease affects 5.4 million Americans (“How Gait” par. 1), and an estimated 200 billion dollars for treating it in the U.S. has to spend in 2012 (Park par. 3).

Lack of sleep does not only affect the brain on which it decreases speed and accuracy of thinking, the ability of speech, creative thinking, and the efficency of learning and remembering. It also increases health problems including diabetes, high blood pressure, heart disease, obesity,immune problems,  and even early death.

Knutson, a sleep anthropologist of the University of Chicago, says, "People who habitually sleep six or fewer hours a night are at increased risk of developing diabetes” (Schardt 9). According to International Diabetes Federation, the amount of people with obstructive sleep apnea—a disorder in which breathing difficulties during sleep lead to frequent arousals—having diabetes is up to 40 percent, and more than haft of Type 2 (adult-onset) diabetes sufferers have trouble with sleep (Clemmitt 131). Knutson also says, "If lack of sleep leads to the development of insulin resistance, that might explain why it could raise the risk of diabetes” (Schardt7). A research shows that sleep deprivation increases endogenous glucose production by approximately 22 percent and reduces insulin sensitivity by approximately 20 percent (“Risk-Diabetes” 140). The increasing of glucose, the high-energy carbohydrate that cells use for fuel, and reducing of sensibility of insulin, a hormone in the body which controls the amount of sugar in the blood, cause the glucose process to slow and raise the risk of having or developing diabetes.

There is a link between high blood pressure and insufficient sleep, according to a new study published in Hypertension. When people have full sleep, their heart beats slower. This reduces blood pressure. On the contrary, suffering lack of sleep may negatively influence blood-pressure-regulating organs such as the kidneys, leading to higher daytime measurements (Bergen par. 1).

Sleep deprivation causes diabetes and high blood pressure, and these health problems are one of the major risk factors for heart disease. In fact, there is a connection between obstructive sleep appnea and heart disease. People who have this type of sleep deprivation experience multiple awakenings each night because of the closing of their airway during sleeping. In addition, as previously mentioned, these sleep-deprived people also experience brief surges in blood pressure.This can result in the chronic elevation of blood pressure known as hypertension, one of main reasons of heart disease (“Sleep and Disease Risk” par. 11). Furthermore, without resting, your heart muscle has to work “overtime”. It reacts with the overtime working by making muscle stronger. This causes high blood pressure or thickening of the heart muscle and then leads to heart disease as well (Breuspar. 8).

Several studies have linked insufficient sleep and weight gain. Marie-Pierre St-Onge, a sleep and obesity researcher at Columbia University in New York, says, "There's substantial evidence from experiments in people that sleep deprivation leads to an increase in food intake" (Schardt 10). In her recent study, people with the age from 30 to 49 eat an average of 300 more calories if they sleep just four hours a night during four nights. Also, in an earlier study at the University of Chicago, men and women who sleep less than five hours a night for two weeks eat 220 more calories a day than seven-hour-sleep people (Schardt 10). Sleep deprivation reduces the level of leptin, a hormone involves in the regulation of hunger, but it increases the level of ghrelin, a hormone produces in the stomach that increases the desire to eat. As a result, lack of sleep triggers metabolic changes that cause sleep-deprived people tend to eat much more food than they need and store fat more easily (“Sleep and Disease Risk” par. 7).

In fact, the influence of sleep deprivation over weight gain is very clearly in the children and teenagers. The increase of BMI, an estimate of an individual’s relative body fat calculated from his or her height and weight, is much higher among younger children (3-8 years old) than the older ones (8-13 years old) (Orzeł-Gryglewska 101). The recently published results of a six-year research also present a link between sleep time and body mass gain. For the sleep-deprived individuals, the risk of gaining weight by 5 kg is by 35 percent, and the risk of obesity is by 27 percent in compare with healthy individuals (Orzeł-Gryglewska 101). In addition, lack of sleep may make us feel so tired that we cannot do exercise to burn off these extra calories (“Sleep and Disease Risk” par. 7).

Normally, people would like to sleep or to take a nap when they feel sick. They then feel fatigue because of the fighting against infection of immune system. As previously mentioned, in stage 3 and 4 of NREM, the immune system is reinforced, so slack of sleep shortens the NREM process, and the system becomes less strong than normal.

In addition, a research shows that sleep deprivation hurts the immune system. In fact, lack of sleep causes cell-mediated immunity (T_H1 activity) more active than humoral immunity (T_H2 activity). T_H1 cells are a type of helper cells which produce cytokines, the principal messengers of the immune system, to stimulate cellular immunity. T_H2 cells are also helper cells but activate humoral immunity associated with antibody production. When the unbalance between two major types of immune activity occurs, immune system can be weakened and work ineffectively. Furthermore, in two different studies, the antibody of sleep-deprived people reacts to two vaccinations against hepatitis A virus and influenza virus much slower than healthy people (Ganz 22). The result also shows that lack of sleep influences the immune system.

Insufficient sleep causes a lot of health problems including diabetes, high blood pressure, heart disease, and obesity. As a result of these health problems, it is certain that poor sleep is also associated with lower life expectancy. Daniel Jones, president of the American Heart Association and dean of the School of Medicine at the University of Mississippi in Jackson, said that obesity kids would die in their middle age at a high rate because of heart disease and stroke if nothing was done to prevent the epidemic  (Nanci par. 10). The research of pediatric endocrinologist David Ludwig, an associate professor of pediatrics at Harvard Medical School, also shows that the age of weighty children can reduce by two or five years if no solution is given for the obesity plague (Nanci par. 3). Also, diabetes causes the significant and negative changes in body, not only anatomy but also physiology. This causes life expectancy shorter. For instance, diabetic people from 55 to 64 ages lose 8 years to live than healthy people. In other words, a 57-year-old person with the disease is like a 65-year-old healthy person in biological age (Albright 1482).

We have to suffer so many negative things when we don’t have enough time to sleep. Sleep deprivation influences our brain and health negatively and significantly. It reduces the speed and accuracy of thinking, affects the ability of speech and creative thinking, and limits the ability of learning and memorizing. It causes health problems including diabetes, high blood pressure, heart disease, obesity, and the decline of immune system and life expectancy. Is it worth if we sacrifice our brain and health to take just few more wakefulness hours for something? Chiara Cirelli, a professor of psychiatry at the University of Wisconsin-Madison, says, "The message is you need to take sleep very seriously. When you're starting to nod off, it's too late. Even before that, there may be impairment. Respect your need for sleep" (Weise par. 12). 

References

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