The reasons are seemingly obvious.
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Second, there is the issue of work: not only the porous borders between when you start and finish, but longer commuter times, too. No one wants to give up time with their family or entertainment, so they give up sleep instead. And anxiety plays a part. Alcohol and caffeine are more widely available. All these are the enemies of sleep. But Walker believes, too, that in the developed world sleep is strongly associated with weakness, even shame. They would rather wait 45 minutes for the confessional.
We chastise people for sleeping what are, after all, only sufficient amounts. We think of them as slothful. But that notion is quickly abandoned [as we grow up]. Humans are the only species that deliberately deprive themselves of sleep for no apparent reason. The world of sleep science is still relatively small. Walker, who is 44 and was born in Liverpool, has been in the field for more than 20 years, having published his first research paper at the age of just It was while working on this that he stumbled into the realm of sleep.
One night, however, he read a scientific paper that changed everything. I realised my mistake. I had been measuring the brainwave activity of my patients while they were awake, when I should have been doing so while they were asleep. Sleep, it seemed, could be a new early diagnostic litmus test for different subtypes of dementia.
After this, sleep became his obsession. I was always curious, annoyingly so, but when I started to read about sleep, I would look up and hours would have gone by. No one could answer the simple question: why do we sleep? That seemed to me to be the greatest scientific mystery. I was going to attack it, and I was going to do that in two years. But I was naive. Formerly a professor of psychiatry at Harvard Medical School, he is now professor of neuroscience and psychology at the University of California.
Does his obsession extend to the bedroom? Does he take his own advice when it comes to sleep? I take my sleep incredibly seriously because I have seen the evidence. There is, however, a sting in the tale. His problem then, as always in these situations, was that he knew too much. His brain began to race. In the end, it seems, even world experts in sleep act just like the rest of us when struck by the curse of insomnia. He turned on a light and read for a while. Will Why We Sleep have the impact its author hopes?
But what I can tell you is that it had a powerful effect on me. After reading it, I was absolutely determined to go to bed earlier — a regime to which I am sticking determinedly. In a way, I was prepared for this. But in another way, it was unexpected. I am mostly immune to health advice. The evidence Walker presents, however, is enough to send anyone early to bed. Without sleep, there is low energy and disease. An organism whose circadian clock exhibits a regular rhythm corresponding to outside signals is said to be entrained ; an entrained rhythm persists even if the outside signals suddenly disappear.
If an entrained human is isolated in a bunker with constant light or darkness, he or she will continue to experience rhythmic increases and decreases of body temperature and melatonin, on a period which slightly exceeds 24 hours. Scientists refer to such conditions as free-running of the circadian rhythm. Under natural conditions, light signals regularly adjust this period downward, so that it corresponds better with the exact 24 hours of an Earth day. The circadian clock exerts constant influence on the body, effecting sinusoidal oscillation of body temperature between roughly Circadian rhythm exerts some influence on the nighttime secretion of growth hormone.
The circadian rhythm influences the ideal timing of a restorative sleep episode. REM sleep occurs more during body temperature minimum within the circadian cycle, whereas slow-wave sleep can occur more independently of circadian time. The internal circadian clock is profoundly influenced by changes in light, since these are its main clues about what time it is. Exposure to even small amounts of light during the night can suppress melatonin secretion, and increase body temperature and wakefulness.
Short pulses of light, at the right moment in the circadian cycle, can significantly 'reset' the internal clock. Modern humans often find themselves desynchronized from their internal circadian clock, due to the requirements of work especially night shifts , long-distance travel, and the influence of universal indoor lighting. Conversely they can have difficulty waking up in the trough of the cycle. Generally speaking, the longer an organism is awake, the more it feels a need to sleep "sleep debt". This driver of sleep is referred to as Process S.
The balance between sleeping and waking is regulated by a process called homeostasis. Induced or perceived lack of sleep is called sleep deprivation. Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus , allowing for inhibition of the ascending reticular activating system. Sleep deprivation tends to cause slower brain waves in the frontal cortex , shortened attention span, higher anxiety, impaired memory, and a grouchy mood. Conversely, a well-rested organism tends to have improved memory and mood.
There is disagreement on how much sleep debt it is possible to accumulate, and whether sleep debt is accumulated against an individual's average sleep or some other benchmark. It is also unclear whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. Sleep debt does show some evidence of being cumulative. Subjectively, however, humans seem to reach maximum sleepiness after 30 hours of waking.
One neurochemical indicator of sleep debt is adenosine , a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine levels increase in the cortex and basal forebrain during prolonged wakefulness, and decrease during the sleep-recovery period, potentially acting as a homeostatic regulator of sleep. Humans are also influenced by aspects of social time , such as the hours when other people are awake, the hours when work is required, the time on the clock, etc.
Time zones , standard times used to unify the timing for people in the same area, correspond only approximately to the natural rising and setting of the sun. In polyphasic sleep , an organism sleeps several times in a hour cycle, whereas in monophasic sleep occurs all at once. Under experimental conditions, humans tend to alternate more frequently between sleep and wakefulness i.
Bimodal sleep in humans was more common before the industrial revolution. Different characteristic sleep patterns, such as the familiarly so-called " early bird " and " night owl ", are called chronotypes. Genetics and sex have some influence on chronotype, but so do habits. Chronotype is also liable to change over the course of a person's lifetime.
Seven-year-olds are better disposed to wake up early in the morning than are fifteen-year-olds. Many people experience a temporary drop in alertness in the early afternoon, commonly known as the "post-lunch dip". While a large meal can make a person feel sleepy, the post-lunch dip is mostly an effect of the circadian clock. At those two times, the body clock is activated. At about 2 p. At about 2 a. It is hypothesized that a considerable amount of sleep-related behavior, such as when and how long a person needs to sleep, is regulated by genetics.
Researchers have discovered some evidence that seems to support this assumption. Neurotransmitters, molecules whose production can be traced to specific genes, are one genetic influence on sleep which can be analyzed. The circadian clock has its own set of genes. The quality of sleep may be evaluated from an objective and a subjective point of view. Objective sleep quality refers to how difficult it is for a person to fall asleep and remain in a sleeping state, and how many times they wake up during a single night. Poor sleep quality disrupts the cycle of transition between the different stages of sleep.
A study by A. Harvey et al. Homeostatic sleep propensity the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode must be balanced against the circadian element for satisfactory sleep. The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening:  maximum concentration of the hormone melatonin, and minimum core body temperature.
Human sleep needs vary by age and amongst individuals; sleep is considered to be adequate when there is no daytime sleepiness or dysfunction.
As They Slept - Part 4
Moreover, self-reported sleep duration is only moderately correlated with actual sleep time as measured by actigraphy ,  and those affected with sleep state misperception may typically report having slept only four hours despite having slept a full eight hours.
Researchers have found that sleeping 6—7 hours each night correlates with longevity and cardiac health in humans, though many underlying factors may be involved in the causality behind this relationship.
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Sleep difficulties are furthermore associated with psychiatric disorders such as depression , alcoholism , and bipolar disorder. Dysregulation detected by EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to latency, distribution across the night and density of eye movements. By the time infants reach the age of two, their brain size has reached 90 percent of an adult-sized brain;  a majority of this brain growth has occurred during the period of life with the highest rate of sleep.
The hours that children spend asleep influence their ability to perform on cognitive tasks. Sleep also influences language development. To test this, researchers taught infants a faux language and observed their recollection of the rules for that language. There is also a relationship between infants' vocabulary and sleeping: infants who sleep longer at night at 12 months have better vocabularies at 26 months. Children need many hours of sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.
The human organism physically restores itself during sleep, healing itself and removing metabolic wastes which build up during periods of activity. This restoration takes place mostly during slow-wave sleep , during which body temperature, heart rate, and brain oxygen consumption decrease. The brain, especially, requires sleep for restoration, whereas in the rest of the body these processes can take place during quiescent waking. In both cases, the reduced rate of metabolism enables countervailing restorative processes. While awake, metabolism generates reactive oxygen species , which are damaging to cells.
During sleep, metabolic rates decrease and reactive oxygen species generation is reduced allowing restorative processes to take over. The sleeping brain has been shown to remove metabolic waste products at a faster rate than during an awake state. The concentration of the sugar compound glycogen in the brain increases during sleep, and is depleted through metabolism during wakefulness. Studies suggest that sleep deprivation may impair the body's ability to heal wounds.
It has been shown that sleep deprivation affects the immune system. The effect of sleep duration on somatic growth is not completely known. One study recorded growth, height, and weight, as correlated to parent-reported time in bed in children over a period of nine years age 1— It was found that "the variation of sleep duration among children does not seem to have an effect on growth. It has been widely accepted that sleep must support the formation of long-term memory, and generally increasing previous learning and experiences recalls.
However, its benefit seems to depend on the phase of sleep and the type of memory. Regarding to declarative memory, the functional role of SWS has been associated with hippocampal replays of previously encoded neural patterns that seem to facilitate long-term memories consolidation. Reactivation of memory also occurs during wakefulness and its function is associated with serving to update the reactivated memory with new encoded information, whereas reactivations during SWS are presented as crucial for memory stabilization.
Furthermore, nocturnal reactivation seems to share the same neural oscillatory patterns as reactivation during wakefulness, processes which might be coordinated by theta activity. During sleep, especially REM sleep, people tend to have dreams: elusive first-person experiences which seem realistic while in progress, despite their frequently bizarre qualities.
Dreams can seamlessly incorporate elements within a person's mind that would not normally go together. They can include apparent sensations of all types, especially vision and movement. People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that have been relegated to the unconscious mind , and he used dream interpretation in the form of psychoanalysis in attempting to uncover these desires.
Counterintuitively, penile erections during sleep are not more frequent during sexual dreams than during other dreams. Neatly, this theory helps explain the irrationality of the mind during REM periods, as, according to this theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it. This would explain the odd nature of many dreams. Using antidepressants , [ clarification needed ] acetaminophen , ibuprofen , or alcoholic beverages is thought to potentially suppress dreams, whereas melatonin may have the ability to encourage them.
Insomnia is often treated through behavioral changes like keeping a regular sleep schedule, avoiding stimulating or stressful activities before bedtime, and cutting down on stimulants such as caffeine. The sleep environment may be improved by installing heavy drapes to shut out all sunlight, and keeping computers, televisions and work materials out of the sleeping area. A review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the exception of heavy exercise taken shortly before bedtime, which may disturb sleep.
However, there is insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep. Although these nonbenzodiazepine medications are generally believed to be better and safer than earlier generations of sedatives, they have still generated some controversy and discussion regarding side-effects. White noise appears to be a promising treatment for insomnia. Obstructive sleep apnea is a condition in which major pauses in breathing occur during sleep, disrupting the normal progression of sleep and often causing other more severe health problems.
Apneas occur when the muscles around the patient's airway relax during sleep, causing the airway to collapse and block the intake of oxygen. When several of these episodes occur per hour, sleep apnea rises to a level of seriousness that may require treatment. Diagnosing sleep apnea usually requires a professional sleep study performed in a sleep clinic, because the episodes of wakefulness caused by the disorder are extremely brief and patients usually do not remember experiencing them.
Instead, many patients simply feel tired after getting several hours of sleep and have no idea why. Major risk factors for sleep apnea include chronic fatigue, old age, obesity and snoring. Fatal familial insomnia , or FFI, an extremely rare genetic disease with no known treatment or cure, is characterized by increasing insomnia as one of its symptoms; ultimately sufferers of the disease stop sleeping entirely, before dying of the disease. Somnambulism, known as sleep walking, is also a common sleeping disorder, especially among children.
Older people may be more easily awakened by disturbances in the environment  and may to some degree lose the ability to consolidate sleep. Drugs which induce sleep, known as hypnotics , include benzodiazepines , although these interfere with REM;  Nonbenzodiazepine hypnotics such as eszopiclone Lunesta , zaleplon Sonata , and zolpidem Ambien ; Antihistamines , such as diphenhydramine Benadryl and doxylamine ; Alcohol ethanol , despite its rebound effect later in the night and interference with REM;   barbiturates , which have the same problem; melatonin , a component of the circadian clock, and released naturally at night by the pineal gland ;  and cannabis , which may also interfere with REM.
Stimulants , which inhibit sleep, include caffeine , an adenosine antagonist; amphetamine , MDMA , empathogen-entactogens , and related drugs; cocaine , which can alter the circadian rhythm,   and methylphenidate , which acts similarly; and other analeptic drugs like modafinil and armodafinil with poorly understood mechanisms. Dietary and nutritional choices may affect sleep duration and quality. One review indicated that a high carbohydrate diet promoted shorter onset to sleep and longer duration sleep than a high fat diet.
Research suggests that sleep patterns vary significantly across cultures. The boundaries between sleeping and waking are blurred in these societies. Some societies display a fragmented sleep pattern in which people sleep at all times of the day and night for shorter periods.
In many nomadic or hunter-gatherer societies, people will sleep on and off throughout the day or night depending on what is happening. Historian A. Roger Ekirch thinks that the traditional pattern of " segmented sleep ," as it is called, began to disappear among the urban upper class in Europe in the late 17th century and the change spread over the next years; by the s "the idea of a first and second sleep had receded entirely from our social consciousness. In some societies, people sleep with at least one other person sometimes many or with animals. In other cultures, people rarely sleep with anyone except for an intimate partner.
In almost all societies, sleeping partners are strongly regulated by social standards. For example, a person might only sleep with the immediate family , the extended family , a spouse or romantic partner, children, children of a certain age, children of specific gender, peers of a certain gender, friends, peers of equal social rank, or with no one at all.
Sleep may be an actively social time, depending on the sleep groupings, with no constraints on noise or activity. People sleep in a variety of locations. Some sleep directly on the ground; others on a skin or blanket; others sleep on platforms or beds. Some sleep with blankets, some with pillows, some with simple headrests, some with no head support.
These choices are shaped by a variety of factors, such as climate, protection from predators, housing type, technology, personal preference, and the incidence of pests. If you love to move to music, go dancing or take a dance class. Dance classes are also a great way to extend your social network. These ball games are gentle ways to exercise. Walking adds an aerobic bonus and spending time on the course with friends can improve your mood.
Cycling or running. If you are in good shape, you can run and cycle until late in life. Both can be done outdoors or on a stationary bike or treadmill. A study at Northwestern University found that aerobic exercise resulted in the most dramatic improvement in quality of sleep, including sleep duration, for middle-aged and older adults with a diagnosis of insomnia.
Stress and anxiety built up during the day can also interfere with sleep at night. Try to stay out of your head and focus on the feelings and sensations in your body instead. Make relaxation your goal, not sleep. Try a relaxation technique such as deep breathing or meditation, without getting out of bed. Although not a replacement for sleep, relaxation can still help rejuvenate your body. Do a quiet, non-stimulating activity.
But keep the lights dim and avoid screens. Postpone worrying. If you wake during the night feeling anxious about something, make a brief note of it on paper and postpone worrying about it until the next day when it will be easier to resolve. Write down when you use alcohol, caffeine, and nicotine, and keep track of your medications, exercise, lifestyle changes, and recent stresses.
Your doctor may then refer you to a sleep specialist or cognitive behavioral therapist for further treatment, especially if insomnia is taking a heavy toll on your mood and health. In fact, they can actually make insomnia worse in the long-term. A study at Harvard Medical School found that CBT was more effective at treating chronic insomnia than prescription sleep medication—but without the risks or side effects. CBT can be conducted individually, in a group, or even online. National Institute on Aging.
National Sleep Foundation. The Mayo Clinic. Diet, Exercise, and Sleep — Describes the interrelationships between sleep, nutrition, and exercise. Stress Less, Sleep More — Tips for reducing stress to promote better sleep, including the use of acupressure.
Thatcher: Can people get by on four hours' sleep? - BBC News
Authors: Melinda Smith, M. Last updated: June How many hours of sleep do older adults need? Aerobic exercise helps older adults sleep better A study at Northwestern University found that aerobic exercise resulted in the most dramatic improvement in quality of sleep, including sleep duration, for middle-aged and older adults with a diagnosis of insomnia. The participants exercised for two minute sessions or one tominute session four times per week. They worked at 75 percent of their maximum heart rate on at least two activities including walking or using a stationary bicycle or treadmill.
Their sleep quality improved from a diagnosis of poor sleeper to good sleeper. They reported fewer depressive symptoms, more vitality, and less daytime sleepiness. Source: National Sleep Foundation. Other resources.