Sleep is as important to human health as food and water. Sleep requirements differ from one to another, depending on age, physical activity levels, general health status and other individual factors. In general, children and teenagers need about nine to ten hours of sleep per night, and adults need about eight hours. However, 40% of American (100 million people) adults may be putting themselves at risk for injury, health and behavior problems because they aren't meeting their minimum sleep need in order to be fully alert the next day. Lack of essential amount of sleep even in a period of time is termed sleep deprivation. Sleep deprivation is a result of life style, physical and metal disorder, and consequently affects people’s health and normal life.

    Sleep deprivation is often a direct result of lifestyle choices. Drinking caffeine before bedtime will artificially create energy and keep people awake. Overuse of alcohol may lead to poor quality of sleep though certain amount of alcohol is helpful for sleeping.  Staying up late to socialize or entertain such as chatting online or through phone, hanging in bars, watching television or reading good books may excite certain brain areas, and therefore causes sleep disorder including difficult being asleep and less deep sleep. In addition, working shifts in many professions easily disrupt normal sleep-wake cycles. For example, nurses have jobs and schedules that lead to sleep deprivation. This includes rotating shifts, being on call all night and then working regularly assigned shifts the next day, or working double shifts and having home responsibilities that prevent them from sleeping during precious free hours. International airline attendants or frequent travelers tend to have irregular sleeping patterns because their biological clock has to switch from one time zone to another. People on these occupations find it almost impossible to make up sleep loss during daylight hours. Parents always suffer inadequate sleep when their young children wake up at nights for feeding or comfort. Students sacrifice required sleep to prepare their exams or papers, which will negatively influence their health.

Physical discomfort plays critical roles in sleep deprivation. People with colds and stuffy nose are usually not able to breathe smoothly. As a result, heavy breathing, snoring and frequent waking directly fragment sleep. Headache and migraine are also reasons for the prevalence of sleep deprivation, especially among women, though not always vice versa. Sleep does not always relieve fatigue. Sometimes extreme exhaustion in association with sore arms and legs triggers sleep disorder.

There is a close relationship between mind disorder and sleep deprivation. Instead of relaxing mentally and physically, lying in bed worrying robs and disturbs sleep. The more stress and anxiety one experiences, the more one worries, the more depressed one becomes, the less likely he/she will sleep well. Sleep deprivation is also a result of other emotional states such as fear, grief and loneliness. Moreover, sleep may be disrupted for a range of environmental reasons along with related mood swing, for example, because the bedroom is too hot or cold, or because neighbors are too noisy.

    Sleep deprivation is a serious disease and impairs human health in a huge range. The most common physical problems include aching muscles, blurred vision, dizziness, nausea, hand tremors, headache, weight loss or gain. Sleep deprivation weakens the immune system leaving people more vulnerable to other diseases and disorders such as common cold, cardiovascular disease, diabetes, and even cancer. Sleep deprivation adversely affects brain function. For example, a study showed that the brain regions activated in rested subjects doing the arithmetic problems were not active in the sleep-deprived subjects. No other region of the brain became activated when subjects performed arithmetic when sleep-deprived. Subjects had fewer correct answers and omitted more responses when sleepy than when rested. Furthermore, sleep deprivation may be linked to more serious diseases, such as mental illnesses including psychosis, bipolar and even death. Psychologically, decreased mental activity, reduced alertness, impatience, irritability, memory loss, poor judgment, emotional highs and lows, and reduced work efficiency extensively occur to sleep-deprived individuals.  Studies have shown that people who get too little sleep may have higher levels of stress hormone. Therefore, they are easy to be stressed out, anxious and depressed. Sleepy people are less focused and concentrated, and this could not only lead to physical injuries like falls but also become lost on an unfamiliar street. Over 100,000 traffic accidents each year are caused by fatigue and drowsiness, and related reduced alertness. Sleep loss in children and teenagers greatly affects mood, behavior, and academic performance. Poor sleepers are reported being more likely to have a negative self-image and inferior coping behaviors and they have more behavioral problems such as naughtiness, poor self-control and risk-taking behaviors at home and in school.  Researchers suggest that one more hour of sleep helps kids learn and reduces negative feelings.

    Sleep deprivation has become a problem in modern society where people always feel they have too little time for too much work. However, there is truly a two-way street between sleep deprivation and physical and mental health. To keep human body functions properly, sleeping is an effective way to restore energy rather than a waste of time.