women with sleep deprivation

Knowledge Base

We all know how it feels after a sleepless night, but do you know how important a good night’s sleep really is? Read on to learn how much sleep matters!

Alcohol and Sleep

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Alcohol influences sleep significantly. Its most obvious impact is shortening the time to fall asleep (sleep latency), which is why it is a popular aid for people who have difficulty falling asleep.

As well, it increases the amount of deep sleep during the first half of the night. This may be viewed as a sleep quality “improver”, because this type of sleep is restorative. Growth hormone secretion and tissue repair occur during deep sleep.

The downside comes in the second half of the night: fragmented sleep and less overall REM sleep. Lack of REM sleep can cause memory issues, motor skills deterioration and attention deficit. This happens because REM sleep has an important role in promoting learning skills and memory consolidation.

The consumption of alcohol decreases respiratory drive and increases muscle relaxation. This means that alcohol can trigger sleep-related breathing disorders or worsen existing sleep apnea. In addition, it increases a person’s propensity to experience parasomnias such as sleepwalking.

The magnitude of the effects correlates to the amount of alcohol consumed.

Basic Rules for a Good Night’s Sleep

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Sleep hygiene is a set of practices that promote and maintain healthy and restful sleep. People with sleep difficulties have been using them for decades to improve their night time rest and stave off unwanted symptoms of sleep deprivation during the day. The goal is to prevent sleep issues from interfering with daily life.

Start your hygiene check-up by reviewing your bedroom environment.

  • Your bed is comfortable.
  • The ambient temperature is comfortable.
  • The bedroom air is fresh and free of disturbing irritants or odors.
  • The noise level doesn’t annoy or distract you.
  • Use window shades wisely. Keep the room darker by closing the shades when you need to sleep.
  • Keep the television out of the bedroom.

Pay attention to the following factors that interfere with sleep.

  • Your intake of stimulants. You may need to reduce or eliminate foods, drinks or medications that keep you awake, particularly in the latter half of the day. The most notorious example is caffeinated coffee, which many people use as “pick me up” to combat sleepiness.
  • Smoking before bedtime.An unhealthy habit which has an additional deleterious impact on sleep that is less well known: Nicotine is a stimulant.
  • Timing and intensity of exercise. Exercise can improve sleep quality, which in turn facilitates physical recovery. But high-intensity exercise that’s too close to bedtime may interfere with your ability to fall asleep.
  • Use of relaxation techniques. Finding a way to unwind at the end of the day can help you to fall asleep at bedtime. Use whatever works best for you.
  • Alcohol as a sleep aid. The use of alcoholic drinks to assist with falling asleep is a popular but misguided notion. Alcohol may indeed help you to fall asleep, but it’s toxic to sleep quality, making your rest inefficient and fragmented.
  • Heavy meal before bedtime. Eating a large or heavy meal before going to bed can make falling asleep difficult.
  • Lying awake for long periods. Use your bed only for sleeping and intimacy. If you can’t fall asleep, get up and do something relaxing, then go back to bed when you feel ready. Lying in bed and not sleeping for long periods of time can exacerbate sleep difficulties.
  • Daytime napping. Don’t nap during the day. Period.

If you wake up too early every morning:

  • Check environment factors such as noise, pets, etc.
  • If you feel moody, depressed or anxious, consider talking to your physician.

If you have trouble falling asleep, find it very difficult to wake up, and are chronically late or irritable, you may be sleep deprived. To improve things, you need to change your behavior by doing the following:

  • Choose a wake-up time that makes sense in the context of school, work or other obligations.
  • Always wake up at that time. On weekends, don’t let yourself sleep more than 30 minutes past that time.
  • Count backwards from that time based on your sleep needs (at least 7 hours). That’s when you should be in bed and asleep.
  • It may be helpful to limit yourself to 6 hours of sleep initially, and then increase the amount by 15 minutes each week until you reach a duration that satisfies your sleep needs.
  • Follow the other rules of good sleep hygiene.

Biological clocks: sleep wake rhythms

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Many human functions present a cyclic behavior resulting from the existence of certain inner oscillators that coordinate different function. These inner cycle regulators are called biological clocks. One of the most obvious ones is in charge of the sleep-wake cycle. This clock resides in the Suprachiasmatic Nucleus (SCN) of the brain and its period is between 24 and 25 hours. Thus, without any other additional factors, humans would go to sleep progressively about an hour later each day and wake up an hour later. However, humans live their lives in a 24 hours or day-night recurring pattern called a circadian rhythm. The light arriving to the eyes signals the SCN to reset the sleep-wake cycle to a 24 hours one. This influence is mediated by the small pineal gland, which produces a hormone called Melatonin.

This hormone is produced in the dark and its secretion is inhibited by light. Melatonin is connected with the sleep-wake cycle. Exogenous Melatonin may be used as an aid to reset the inner clock when needed, for instance when traveling fast over time zones people suffer from jet lag and have to sync their inner clock to their target time.

Evening type-morning type: Owl vs Lark type

The biological clock dictates to our body and minds when to go to sleep and when to wake up. Normal people are adaptive enough to align their schedule with their inner clock. Most human beings have an inner clock whose period is longer than 24 hours, thus most have a tendency to go to sleep at late hours and wake up relatively late. That is why evening type or night owl type people are prevalent. The opposite works for larks: they are morning types, their clock preference is to go to sleep early and wake up early. These two tendencies are natural and they do not pose a problem as long as there is no interference with daily duties and they do not cause sleep deprivation.

Delayed Sleep Phase

The inner clock dictates sometimes a sleep-wake schedule that is different from the usual prevailing one. There are people who go to sleep at very late hours and wake up late. Their inner clock lacks the ability to sync with the prevailing timings. Their sleep is perfectly normal when they sleep according to their individual settings. However, if they try to go to sleep at a time that is quite usual for others, they have great difficulty falling asleep. When they go to sleep very late, according to their own timing, they fall asleep easily, and they sleep late if they can afford it; if not, they make it for school or for their job, but they are not at their best; or they are late, and that’s bad as well. So, what is the solution? If they can live according to their inner clock, nothing needs to be done. If not, there are a few ways to deal with the problem, but they are tough to implement and they require commitment, at least for a while.

A decision has to be taken and a commitment to stick to the way are prerequisites. Then, If the delay is not very large, not longer than 3-4 hours, one may choose to advance gradually the wake up time and the bedtime (by about half an hour a week), while keeping the wake up time fixed for the entire week, no matter what the fall asleep time is, and avoiding napping; also, avoiding bright light in the evening and late hours and exposing to natural light in the morning. Sometimes an additional bright light source should be used in the morning. In addition, strict adherence to sleep hygiene rules is mandatory.

If the delay is greater, the following procedure may be used: a sequential delay in the bedtime and wake up time by about 1-2 hours daily (basically moving the cycle backwards through a full day), until the target hours are achieved and then sticking to the new times. When this occurs, again, adherence to sleep hygiene rules is mandatory.

Advanced Sleep Phase

Some have an inner clock that makes them feel sleepy early, and when they give in to their natural tendency, they sleep fine and wake up early. This way they give up on socializing during the late part of the day, when most can afford this, and they are up early for their jobs and this way they are dedicated larks. They pay a price too in giving up spending the end of the day with friends or family — quite a price to pay. This tendency, called advanced sleep phase, occurs mainly in the old age, when the clock is advanced naturally, or in a rare inherited state of advanced sleep phase. In both situations one can deal with the problem. The solution is based on gradual delay of the bedtime, using exposure to bright light in the evening.

Chronotherapy that delays the bed time to the desired time gradually is a possible alternative. Melatonin can be added in the morning as an additional measure to delay the sleep time. In addition, strict adherence to sleep hygiene rules is mandatory, except for the napping restriction, which can be relaxed to make staying awake at later hours possible.

Irregular sleep

Sometimes the internal clock does not work; it is broken. In this situation, which may occur very early in life or later, people have a completely chaotic sleep-wake schedule. This is a very rare condition; however, when it occurs, sleep experts and chrono-biologists have to be involved to find the best solution.

How to cope with shift work

The 24 hour a day society requires many to work shifting rounds or night shifts to keep the pace.

This kind of work requirements imposes a great load on every person who needs to work shifts. A great deal of research and trials on how to minimize damage and improve performance did not reach a good solution that can be universally implemented. However, if work shift is needed, then it should allow for regular sleep hours. People should keep regular night shifts or day shifts, if possible.

Sleep-wake schedule should be as regular as possible in order to let workers adapt their sleep-wake pattern to the job requirements. For instance, when working on night shifts, people have to keep performance and attention at a high level, whereas their inner clock is set for sleep. It is recommended to keep the same sleep time during days off. In this way the work and physiology may be kept aligned. It is recommended to have bright light at work during the night, and keep low light and wear dark sunglasses during the day, so as to sync the inner clock with the needs.

Also, the home sleep environment has to be very quiet during the day.
People who work shifts for long periods of time may be at risk of developing insomnia either while shift working, or later when they return to a usual daily work frame.

Jet lag

People living in a given geographic region have their biological clock synchronized with the local time. When traveling and moving fast across several time zones, the synchronization between the biological clock and the geographical one is lost. This occurs only while travelling either Eastbound or Westbound, and does not occur when travelling in the North or South direction, because  then one remains within the home time zone. The severity of the complaints depends upon the direction (Westbound causing less trouble than Eastbound) and the number of time zones crossed. Eastbound has a bigger effect, since travelling in this direction one loses time, and this adds to the influence of the time difference between place of origin and destination. The opposite occurs when the destination is Westbound and one gains time relative to the home place. The severity of the symptoms is variable and includes insomnia, irritability, headache, malfunction of the digestive system, the need to urinate during the night, etc. In addition, conditions on the flight can cause increased exposure to infection, dehydration and more. Resetting of the clock to the destination time requires around a day per 1-2 time zones crossed. One can try to prevent jet lag by starting to adapt gradually to the target destination time a few days ahead of travel, or trying to adapt quickly upon arrival. The post-travel adaptation strategy is preferred by most and includes mainly exposure to outside bright light, which is a powerful resetting agent for the biological clock, and sticking to sleep hygiene rules. Some advocate usage of Melatonin or other sleeping aids for a few days, or until the jet lag complaints fade out.

Early wake up

When people wake up early it is either because their sleep needs have been fulfilled or because their actual sleep needs are reduced. When somebody wakes up early while really needing more time asleep and can’t get back to sleep, there is a problem. Sometimes a mood problem can explain the difficulty. This problem needs attention, evaluation and appropriate management.

Daytime Sleepiness

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Daytime sleepiness is the propensity to fall asleep at inappropriate times during the day.

The degree of daytime sleepiness correlates directly to the amount and quality of sleep during the previous night. The duration people need to stay awake varies with each individual; but surveys and research indicate most people perform optimally with 7.5 – 8.5 hours. Any sleep loss leads to immediate sleepiness. By the same token, the opposite is true: An extension of sleep duration can alleviate drowsiness and improve performance.

Sleep quality also counts, though this aspect is usually less obvious. Sleep fragmentation (in other words, the lack of continuity) impacts sleep quality and causes drowsiness. There are many possible causes: sleep-related breathing disorders, periodic limb movement during sleep, other medical ailments accompanied by pain or discomfort (e.g., arthritis, back pain, fibromyalgia), and narcolepsy. And that’s far from a complete list.

Individuals are sometimes unaware of their own daytime sleepiness. It may come to their attention after trying to cope with other problems such as decreased performance, hypertension, excessive weight, snoring, and mood disorders.

Fortunately, good objective tests for measuring sleepiness are available. The Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT) are commonly used for this purpose.

Scientifically-validated questionnaires such as the Epworth Sleepiness Scale (ESS) and the Stanford Sleepiness Scale (SSS) are also useful for evaluating sleepiness. As well, alertness can be measured using a visual analog scale (VAS).

If daytime sleepiness is present, the underlying cause(s) should be investigated and identified. Appropriate treatment(s) or lifestyle changes can improve sleep duration and quality, thereby leading to better health, improved performance, and a new sense of wellbeing.

Early Awakenings

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When a person wakes up early, it’s usually because his/her sleep needs have been met or those needs are reduced. If someone wakes up too early and needs more sleep, but can’t go back to sleep, something is wrong. Sometimes the cause is a mood disorder. Notwithstanding the reason, this kind of difficulty needs attention, evaluation and appropriate management.

Evening Type or Morning Type? Owls versus Larks

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Our biological clock tells our body and mind when to go to sleep and when to wake up. If that inner clock doesn’t quite synchronize with life’s obligations, normal people will be able to adapt. But they may not always feel great throughout the day.

Owls (or night owls or evening types) feel best and most alert during late hours. They prefer to have their main meal late in the day and usually skip breakfast. A cup of coffee is often their morning meal. But they do need an alarm clock in the morning to ensure they rise to meet their daily obligations.

In contrast, larks (or morning types) wake up early and are at their best during the first part of the day. They eat breakfast and prefer to retire relatively early, after a light dinner.

Owls predominate because humans have an inner clock with a period slightly longer than 24 hours. That causes a tendency to stay up a bit later and wake up later each day. Owl and lark tendencies are natural and are not considered as problems unless they cause sleep deprivation or interference with daily routines.

Factors that influence human sleep

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There is no standard for the amount of sleep an individual requires. Each person is unique. In simple terms, you need enough sleep to avoid drowsiness and to perform at optimal efficiency during the day. That need changes with age, so what works best in one stage of your life may not be appropriate for another. At the extremes of a distribution across large populations are normal people who need as little as 4 hours or as much as 12 hours.

A majority of people do very well with 7½ to 8 hours of sleep. But use those numbers only as a starting point until you determine if that range is appropriate for you. Although you can ignore your body’s need for a certain amount of rest through motivation and sheer force of will, doing so isn’t conducive to good health or a vibrant existence.

Our “always on” culture has permeated traditional barriers between work time, family time, playtime, and rest. Sometimes we’re trying to do two or three things at once, or we’re struggling to meet an unnatural (and occasionally unrealistic) expansion of obligations. The result is that more of us are carrying sleep debts or adding to them faster than ever before. Sleeping late on the weekends may seem to help, but in fact it’s only paying interest on the debt, so to speak.

Sleep deprivation can have serious consequences for mental and physical health.

You cannot perceive, in precise terms, how much sleep you actually need. The only way of evaluating that in a scientific manner is to sleep for several nights without wakeup or other constraints. After the sleep debt is replenished, your natural need for sleep will take over and yield an accurate duration.

How Cognitive Behavioral Therapy (CBT) for Insomnia works

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Insomnia and Behavioral Sleep Medicine Program

In the past three decades research has shown that non-drug treatments for insomnia can improve sleep in all age groups.  Non-drug treatment is also available to enhance the medical treatment of sleep apnea, which is often associated with non-restorative sleep and excessive daytime sleepiness.  Millions of Americans experience difficulties sleeping at night or wake up un-refreshed in the morning.  Many continue to suffer because they are unaware that effective treatments exist.

The Insomnia and Behavioral Sleep Medicine Program at the Stanford Sleep Disorders Clinic is helping people who suffer from insomnia and other sleep disorders.

Cognitive Behavioral Therapy (CBT) for Insomnia 
Cognitive behavioral therapy guides patients through a series of changes in sleep-related behaviors. The focus is on addressing the three factors that contribute to the persistence of insomnia:

  • conditioned arousal,
  • habits that were developed in an effort to improve sleep but have become ineffective, and
  • sleep-related worry and other sources of heightened arousal.

The therapist identifies the most relevant targets for behavior changes and helps patients overcome obstacles to making the necessary and often difficult changes in sleep-related behaviors. This means that individual patients can concentrate their energy on changes that are most likely to produce improvements in their sleep.

Sometimes the therapist helps patients re-evaluate beliefs about sleep that might be causing unnecessary anxiety.

The majority of patients respond to this treatment fairly quickly. Some experience significant changes after only two therapy sessions. Most improve after four to six sessions, but some might need more. Both group and individual treatments are effective.

Below is a list of some of the instructions and procedures used in this therapy:

Stimulus Control
This set of instructions addresses conditioned arousal. It was developed by Richard Bootzin. They are designed to strengthen the bed as a cue for sleep and weaken it as a cue for wakefulness. The key instructions are:

  • Establish a regular morning rise time. This will help strengthen the circadian clock-regulating sleep and wakefulness. Ideally, bedtime should also be regular, but for people with insomnia, it is impossible to actually fall asleep around the same time nightly. When insomnia resolves, regular bedtime can further strengthen the circadian rhythm.
  • Go to bed only when sleepy. This increases the probability that you will fall asleep quickly. It is important to distinguish between fatigue and sleepiness. Fatigue is a state of low energy, physical or mental. Sleepiness is a state of having to struggle to stay awake. Dosing off while watching TV or as a passenger in a car involve sleepiness. People with insomnia often feel tired but “wired” (i.e., not sleepy) at bedtime.
  • If unable to fall asleep, either at the beginning or in the middle of the night, get out of bed and return to bed only when sleepy again.
  • Avoid excessive napping during the day. A brief nap (15 to 30 minutes), taken approximately 7 to 9 hours after rise time, can be refreshing and is not likely to disturb nocturnal sleep.

Sleep Restriction
This procedure, developed by Arthur Spielman, is designed to eliminate prolonged middle of the night awakenings. It doesn’t aim to restrict actual sleep time, but rather to initially restrict the time spent in bed. Subsequent steps consist of gradually increasing the time spent in bed. The initial time in bed is usually the average nightly total sleep time over the last week. However, the time allowed in bed should not be less than 5.5 hours, even for people who sleep less than 5.5 hours per night.

For example, consider a person who goes to bed at 11:00 p.m. and gets out of bed at 8:00 a.m., but sleeps on average only 6 hours per night. During the first step of this procedure, this person will be in bed only 6 hours (e.g., 12:00 am to 6:00 am). This sounds harsh, but after a week or so there will be a marked decrease in time spent awake in the middle of the night.

Usually, people experience marked improvement in the quality of sleep after a week of restricted time in bed, but they also realize that they are not getting enough sleep. In this case, the next step is to gradually extend the time spent in bed by 15 to 30 minutes, as long as wakefulness in the middle of the night remains minimal.

Each new extension of the time in bed is followed for at least a week before progressing to the next extension. The decision as to when to extend the time in bed is based on the percentage of the time slept out of the time spent in bed. This is called sleep efficiency. If the average sleep efficiency is 85% or higher, then the time in bed is extended. If it is below 80%, then the time is bed is further restricted.

Otherwise, the time in bed remains unchanged. There are several variants of this procedure, and the therapist chooses the one that best fits an individual patient. In all variants, the procedure continues until one reaches a point after which no further extension is necessary because the amount of sleep obtained is sufficient for optimal daytime function.

Reducing Sleep-Interfering Arousal/Activation
This includes a variety of relaxation techniques, stress management skills, and reducing sleep-related worries. The behavioral sleep medicine specialist uses cognitive therapy to reduce arousal by helping patients shift from “trying hard to sleep” to “allowing sleep to happen.” In addition, the following can also facilitate sleep:

  • Use the hour before bedtime to unwind from the day’s stresses. This down time will allow sleepiness to surface and will, therefore, facilitate sleep onset. This is a time to engage in activities that are enjoyable yet calming.
  • Avoid clock watching. Turn the clock around so you cannot see the time yet you can still use it as an alarm. A recent study showed that volunteers who were asked to monitor a digital clock at bedtime took longer to fall asleep than those monitoring a similarly looking device that displayed random digits.
  • Avoid exercise within four hours before bedtime.
  • Make sure that the sleep environment is safe, quiet and pleasant.

About Foods and Substances

  • Alcohol: Alcohol speeds sleep onset, but this positive effect is counteracted by increased wakefulness in the second half of the night.
  • Stimulants: Caffeine has a rather long half-life (about 6 to 8 hours). People’s sensitivity to the effects of caffeine vary. Those with caffeine sensitivity should be particularly careful to avoid caffeine after lunch. (The amount of caffeine in different drinks and recommendations regarding caffeine consumption can be found on the National Sleep Foundation website.) Certain prescription and non-prescription drugs contain caffeine and whenever possible should be avoided close to bedtime. Nicotine and nicotine withdrawal can also interfere with sleep.
  • Eating at night: Digestion slows down during sleep, and indigestion, caused by undigested food, can disrupt sleep. Eating in the middle of the night sends the body an alerting signal.

Taking the Biological Clock Into Account
Bedtime and rise time should be congruent with one’s circadian clock. When the desired bedtime and rise time are not aligned with the circadian clock, the therapist can use procedures to shift the circadian clock, such as properly timed exposure to bright light.

Professional help should be sought by people who find it impossible to follow the above recommendations consistently. For example, some people say they never get sleepy. Others find it too hard to get out of bed at the same time every day.

Therapists with special training in sleep disorders and behavioral sleep medicine are best suited to help people with insomnia because they possess knowledge in both the science of sleep and the science of behavior change. The American Academy of Sleep Medicine has established a certification in Behavioral Sleep Medicine and maintains a list of certified specialists and their geographic location on its website.

How human beings sleep

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When we look at human beings from a certain perspective, it appears that there are two different normal states of being: sleep and wakefulness. Looking closer into these two different states, it becomes clear that sleep is not a homogeneous entity, but it consists of two distinguished phases: REM sleep and Non-REM sleep, and these are as different as sleep is from wakefulness.


Adult human beings spend about two-thirds of their day awake. This state is characterized by different degrees of physical activity or even quiet rest, with muscles being active, mostly in upright position, with brain active and thinking analytically in a very well structured and understandable way, and memory functioning normally. Heart rate and respiration vary according to instantaneous needs, eyes move rapidly to allow visual information coming from the environment.

Non-REM sleep is very different, as we are quiet and recumbent, muscles at resting, but with moving capability spared. Brain activity is at lowest, thought content is structured and analytical, as during wakefulness. Sensory-motor disengagement from the environment is dependent on the sleep depth. There are varying awakening thresholds. Heart rate and respiration are regular and temperature control is similar to that at wakefulness level. Eye movements are absent. By contrast, during REM sleep the body is usually quiet and recumbent, muscle activity is inhibited and normally voluntary muscles are actively kept from contracting, brain is as active and sometimes more so than during wakefulness, but the active centers are different.

The thoughts are bizarre and hyper associative, while memory is impaired. Heart rate and respiration are irregular, body temperature is not well controlled, eye movements are present and rapid, resembling wake time. Human beings are dreaming.

Within that one-third of the time we spend sleeping, one quarter to one third is spent in REM sleep, about two thirds in Non-REM sleep, and around 5%-10% awake. To complicate things a bit more, Non-REM sleep is subdivided into deep sleep and light sleep, with deep sleep taking about one-third of the total Non-REM time. It seems that we have some law of the “one third” working here: one third of the time sleeping, one-third of the sleeping time dreaming, and one-third of the non-dreaming time spent in deep sleep. All these thirds try to find a balance and kind of play a game: when one is ready to sleep, one has some winding down routines, one finds the right position and gradually disconnects from the environment, and finally one enters the kingdom of sleep. All these steps take around ten minutes, and then there is a quick slide into a first period of deep sleep via a short light-sleep phase. When time arrives, there is a resurfacing to almost wakefulness sometimes and a very short episode of dreaming. All this takes about 90-110 minutes and the process restarts with a second cycle, followed by a third one, until a final wake up occurs after about 5-6 cycles normally. The structure of the described sleep cycles changes across the night, with the amount of Non-REM sleep prevailing during the first two-thirds of the night and REM sleep towards morning time. Deep sleep is the prevailing type of Non-REM sleep during the first two cycles and light sleep takes over thereafter.

How Sleep Loss Affects Weight Gain

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In 2010, public health scientists estimated that 1.5 billion of the world’s population was overweight and 500 million were clinically obese. Current trends for Americans were particularly alarming: The estimate is that by 2020 75% of the U.S. population will be overweight or obese. The basic problem has been growing for a long time: an energy imbalance due to the availability of caloric-rich food and decreasing energy expenditures as a result of sedentary lifestyles in an industrialized society.

But that’s not the entire picture. Scientists have learned about another important factor that was not evident until recently: insufficient sleep. They found compelling evidence that sleep loss leads to metabolic disturbances which increase the positive energy imbalance and result in weight gain. This is actually a vicious circle because excess weight is a cause of sleep apnea, which in turn leads to more sleep disruptions.

Recent studies of healthy volunteers with normal weight show that even short periods of sleep deprivation lead to metabolic disturbances of sugars as well as increased appetites.

Other studies show that abnormal sleep-wake cycles (like those related to shift workers) disrupt biological rhythms for sleeping, hunger and eating. When people don’t eat at their normal meal times (for example, eating at night), they gain weight.

When considering how to approach unwanted weight gain, we must now account for three major factors: nutrition, physical activity, and sleep.

How stress affects sleep

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Sleep and stress are tightly connected. Epidemiological studies report a gradual decline in average sleep time in developed countries since the end of the 19th century. That drop has been even more pronounced in the last few decades. At the same time, these studies report a commensurate increase in anxiety. This makes perfect sense because sleep deprivation increases stress, which in turn creates hyperarousal and more sleep difficulties: an inability to fall asleep quickly, insufficient sleep, or lack of refreshing sleep.

Poor sleep, hyperarousal and stress are tightly interwoven, so decreasing the hyperarousal level (as expressed by stress measures) during the day is an important aspect of improving sleep.

Stress is a function of many physiological processes, in particular, the autonomic (involuntary) nervous system. That system takes care of background functions that sustain life (breathing, rhythm and intensity of heartbeats, body temperature regulation, sweating, digestion and blood flow – to name just a few) and the secretion of certain hormones such as adrenaline and cortisol.

The autonomic nervous system has two sides: sympathetic and parasympathetic. The former stimulates heart activity and prepares individuals to “fight or flee” in response to danger, stress or a need to react quickly. The latter does the opposite and is associated with slowing down, relaxing and restoring – essentially “rest and digest”. Overall, this system keeps the human organism safe and performing optimally.

Stress can be assessed in many ways, but most are subjective questionnaires. A few are invasive (blood tests to assess levels of certain hormones, for example.) The mathematical evaluation of heart rate fluctuations that are governed by the autonomic nervous system provides insight into individual stress levels. In practical terms, it’s a feedback mechanism for looking at ways to change stress levels.

Medical sleep studies

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Sleep evaluation and analysis is a relatively new field in Medicine and has emerged as such after the measurement of the electrical activity of the brain (EEG), performed with sensors place on the surface of the head, became available (in the middle of the twentieth century). Based on this new technology, and the possibility of recording on paper a multitude of physiological signals, the understanding of how the body and the brain function during wakefulness and sleep increased dramatically over a few decades. These studies can serve to advance our understanding of what is normal and what malfunctions occur during sleep. Thus sleep studies are widely used to research normal sleep physiology and to diagnose sleep disorders.

A gold standard of sleep evaluation has evolved and remains the standard language for all sleep experts.

A major change occurred during the last decade of the 20th century: digital recording and signal processing devices have replaced the old paper-based devices. In addition, the miniaturization of the devices became very significant, allowing ambulatory testing of people whose sleep needs to be analyzed. However, a conservative approach to sleep evaluation remains in place.

At the end of 1960s sleep experts created a consensus for standard sleep diagnostics and terminology, based on the state of the art technology and knowledge at that time. A new consensus of the American Academy of Sleep Medicine published in 2008 keeps almost all the old standards, in spite the fact that some of them were arbitrarily based on out-of-date technology: for instance, the standard for sleep scoring is a time interval of 30 seconds that fits the length of the paper page of the polygraph. Thus, very limited advantage can be derived in evaluating sleep physiology from the more accurate new digital recordings . This also precludes the possibility of automatic reliable sleep scoring. The gold standard approach is time consuming and depends on the personal attention span and expertise of the scorer. The inter-scorer agreement in this respect, regarding “sleep staging”, is around 80%!

Medical sleep studies include:

1. Gold standard sleep study

widely known as a whole night polysomnography (whole night PSG). It requires to record:

(i)  Signals to allow sleep architecture and quality evaluation including the following

  1. 6 EEG channels at least (not all labs record all of these)
    2. 2 eye movement (EOG) channels
    3. 1 chin muscle activity (EMG) channel

(ii) Signals to allow evaluation of respiration during sleep

  1. Mouth and nose airflow
    2. Nasal pressure
    3. Chest and abdominal movement (2 channels)
    4. Oxygen saturation
    5. Snoring
    6. Body position

(iii) Signals to allow evaluation of limb movements)

  1. 1-4 limb muscle activity (EMG)

(iv)  Other

  1. Electrocardiogram ECG – the electrical activity of the heart – 1-2 channels

Thus a gold standard PSG is performed in a lab in the presence of a technician who attends the recording and is supposed to correct signal quality or disconnection.

Following the recording, the study is scored, manually, or manually with computerized assistance. The gold standard procedure is time consuming, expensive, the scoring is costly and complicated, the accuracy depends on the quality of the recording (which may be quite poor — remember that the recording includes about 19-20 channels), and also human factors related to the scoring person.

The results of this procedure, in spite of its high cost and work involved, are not representative of a regular sleep night. Indeed, the procedure is cumbersome and influences the sleep of the tested person. A regular sleep night involves the natural sleep environment, one’s own bed and the individual usual schedule. All these are absent in a sleep facility. A gold standard in-lab attended study should be reserved for those sleep disorders that are not detectable when using a partial home study. Other objective methods should be used to evaluate sleep and sleep quality in the usual sleep environment. Obstructive Sleep Apnea-Hypopnea can be diagnosed in either setting; insomnia is very inaccurately evaluated in the sleep facility. There are a few sleep disorders related to excessive sleepiness, neurological disorders, suspected nocturnal seizures, that mandate a test in a dedicated sleep facility.

In view of the high cost of the described procedure and due to the fact that many of the people who need sleep diagnostics suffer from sleep-related breathing disorders, there is a continuous pressure to perform partial sleep studies, studies that include only respiratory signals or part of them, studies than can done in the home environment and also are scored easier and more cost effectively.
This new trend is making its way to be widely adopted, but important quality and reimbursement issues remain to be solved in the US. The respective policies differ in countries around the globe.

2. Partial sleep study

Partial Sleep Study includes a few channels dedicated to respiratory function only. It allows, in most cases, accurate and reliable diagnosis of sleep-related breathing disorders. However, when a regular home or in lab partial study is performed, the information regarding sleep micro and macrostructure si lost, making the results less accurate than those of a complete sleep study. This downside of a partial study can be overruled by using sleep structure assessment based on electrocardiogram analysis.

3. Multiple Sleep Latency Test

Multiple Sleep Latency Test is a measure of daytime sleepiness. It is performed in a sleep lab, following a whole night PSG aimed at evaluating sleep and detecting the possible presence of a sleep disorder such as Obstructive Sleep Apnea. The next morning, the patient remains at the sleep lab connected to the polygraph to measure brain activity, eye movements and muscle tonus during 4 to 5 twenty minutes nap opportunities at 2 hours intervals. The time to falling asleep, if at all, during these nap opportunities and the sleep state achieved are measured and compared to normal values in order to evaluate the degree of daytime sleepiness.

4. Maintenance of Wakefulness Test

Maintenance of Wakefulness Test is also a measure of daytime sleepiness. Like the Multiple Sleep Latency Test, it is performed after a whole night gold standard PSG. There are 4 to 5 events at 2 hour difference intervals, when the patient is required to sit in an armchair quietly, without doing anything, in dim light and trying to remain awake. Again the time to falling asleep, if at all, during these events, and the sleep state achieved, are measured and compared to normal values in order to evaluate the degree of daytime sleepiness.


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Is napping good or bad? Human beings have a natural tendency arising from their internal clock to sleep during the night and be awake during the day. There is an additional time during the day when people have a normal tendency to sleep: in the early afternoon, around 2pm our bodies and minds tell us they need a break. The modern society in general overlooks this tendency. Children keep napping until school age. There is a time during the day, around 8 pm, when it is almost impossible to fall asleep. This is the forbidden gate!

One may take a nap if one needs some rest and relaxation. A nap can improve alertness and performance as well as mood when it is really needed. The downside might be some grogginess when waking up, or problems falling asleep at night. So napping may be a good strategy for a person who feels sleepy and is sleep deprived, provided it is kept short, around half an hour or so.

If the sleepiness is a new onset with no change in the overall sleep time, it may indicate there is a sleep or medical disorder involved and one should consult a doctor.

Night Terrors, Sleep Talking, Sleep Walking and Other Strange Night Time Events

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Unusual events occur sometimes at night. These events are intriguing, sometimes funny and other times scary. They are mostly harmless and weird phenomena that we understand only partially and study them, as they represent some kind of a naturally occurring experiment that can teach us a lot.

Night terrors, Sleep talking and Sleep walking are all events that originate in Deep Sleep, mostly during the first third of the night. They are frequent during childhood and usually their prevalence decreases with age, although a small percentage of adults also experience this kind of events. It appears that there is a genetic component to these phenomena. There is no underlying basic disorder and usually no treatment is needed, unless they are very frequent and interfere with the night routine of those sleeping in the same room, house, or environment. The only reason to perform a sleep test may be to rule out epileptic seizures during the night. The sleep environment has to be proofed so the person who has such an episode does not get hurt.

Night terror is frequent in children; they start screaming, crying, being terribly agitated and frightened, they are disconnected from the environment, inconsolable, and any attempt to wake them or to comfort them makes things worse. There is no memory to the event, no sleep disruption, and when they are awake at the end of an episode there is no report of any dreamlike content. Sleep talking and quiet to agitated Sleep walking are an additional spectrum of disorders arising from Deep Sleep in the first third of the night. There is talking and complex motor behavior from quiet to very agitated, and rarely a person can leave the house during an episode. There is no memory of the event in the morning and no sleep disruption. Treatment is not needed if the episodes are not frequent, but the sleep environment has to be safe. The episodes start in late childhood and usually fade out in the late teens, though for some they persist into adulthood.

Nightmares: these are just bad dreams; usually they occur during the last part of the night, and upon awakening from the episode there is a report of a frightening dream.

Sleep paralysis occurs when someone wakes up suddenly from REM sleep, but is unable to move because the REM related muscle inhibition is still on. It may be frightening, but it is harmless; it may be sporadic or recurring in family clusters. Sometimes it is an isolated phenomenon, and other times it occurs as one of the symptoms of Narcolepsy.

REM behavioral disorder presents with agitated motor activity that appears during REM sleep, activity that can cause injury to the patient or to the bed partner. It appears when the muscle inactivation during REM is lost, and people behave violently during sleep. A sleep study can easily diagnose the disorder. It usually originates in a neurological brain problem, for instance, sometimes preceding Parkinson’s disease by many years.

Objective Measures of Daytime Sleepiness

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Sleep physicians have two well-established objective tools at their disposal to measure daytime sleepiness.

Multiple Sleep Latency Test (MSLT)

The MSLT measures daytime sleepiness in a sleep lab after a whole-night polysomnography (PSG), which evaluates sleep and identifies sleep disorders such as obstructive sleep apnea. In the morning, the patient remains connected to the polygraph to measure brain activity, eye movement and muscle tonus during four to five 20-minute nap opportunities at two-hour intervals. The time to sleep onset (if it happens at all) during these opportunities and the sleep stage reached are recorded and compared to normative values. The process yields a validated measure of daytime sleepiness.

Maintenance of Wakefulness Test (MWT)

The MWT is another measure of daytime sleepiness that is also used after a whole-night PSG. Four to five events at two-hour intervals allow the patient to sit quietly in an armchair in dim light for 45 minutes. He/she is asked expressly to make a maximum effort to remain awake. As with the MSLT, the times to sleep onset (if it happens at all) are recorded, along with the sleep stage reached. Those measurements are compared to normative values to evaluate the degree of daytime sleepiness.

Sleep and Driving

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A growing public health concern in many countries is the number of traffic accidents attributable to sleepiness. Drowsiness leads to the same level of impairment as driving under the influence of alcohol; and like alcohol consumption, people seldom perceive the degree of their own impairment. The best estimate is that roughly 25% of fatal accidents are caused by sleep debt. The cost to society of these tragedies is extraordinarily high.

A sleep-deprived individual may be able to avoid falling asleep behind the wheel, but motor coordination, reaction times and judgment are usually compromised significantly. A coffee jolt (or several) will offset sleepiness temporarily, but the safest approach is to stop the vehicle and take a nap.


Unfortunately, there are no sleep-related counterparts to tests that measure blood alcohol levels. That’s why certain professions (professional drivers and airline pilots, to name a few) have regulations that limit operational hours. As well, some states go so far as to screen professional drivers for obstructive sleep apnea-hypopnea, a condition that causes daytime sleepiness.

The best approach for society seems to be ongoing education with repeated public warnings about the dangers of driving while drowsy.


Sleep Disorders

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Sleep disorders can be categorized broadly in one of two ways: medical conditions that originate within sleep; and illnesses and afflictions that originate outside of sleep and cause sleep disruptions.

Sleeprate core technology: a novel sleep assessment method for the home environment

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The Sleep Deprivation Epidemic

Human beings spend about a third of their lives sleeping and around 8 years dreaming. This third of human existence is hidden and its huge influence on the other two thirds is greatly overlooked. Although sleep function and meaning are not entirely understood, there is increasing evidence that this part of human existence is essential and that it is regulated by the nervous system.

Sleep disorders, sleep deprivation, as well as excess sleep, are associated with poor performance, cognitive dysfunction and secondary ill effects on almost every human life aspect, including health, mood, cognitive and physical performance, as well as social coping. Thus poor or insufficient sleep is related with increased cardiovascular morbidity, neuropsychological deficits and increased mortality. The ability to evaluate sleep and diagnose sleep disorders in a simple, scalable, and cost-effective way, without sacrificing clinically relevant information regarding sleep efficiency and sleep structure, means being able to reach a larger proportion of those who have unrecognized sleep problems. The spectrum of sleep disorders is wide and includes: (1) widespread abnormalities that are not labeled as diseases, such as Insomnia of many kinds (affecting up to 40% of the population, with a great majority not getting suitable solutions to their burning problem); (2) disorders related to the fact that vital functions, such as breathing, for example, become vulnerable during sleep, which facilitates the onset of Sleep-Related Breathing Disorders (estimated to affect 4-9% of the population, only 25% of which actually get diagnosed); (3) intrinsic sleep disorders, such Narcolepsy, or (4) secondary sleep disorders resulting from other diseases, such as medical disorders that cause pain, or neurological disorders that cause sleep disruption like Parkinson’s, or mood disorder that lead to Insomnia or to extended sleep, and (5) many others.

Sleep Measurement is painful

A multitude of physiological parameters can be measured during sleep and wakefulness, and some of them are used to allow standard description of different sleep-wake states. Thus, the gold standard sleep disorders diagnostic method is an overnight polysomnography, which requires recordings of electroencephalogram (electrical activity of the brain), electromyogram (electrical activity of muscles), electrooculogram (eye movements), respiratory effort and mouth-nose airflow, as well as electrocardiogram (electrical activity of the heart), oxygen saturation of the blood, limb movements and additional variables, in an attended setting. This procedure is uncomfortable, requires a skilled person to get the patient wired, and the resulting information needs to be recorded, scored, and reviewed by trained personnel. The cost becomes high, the procedure is limited to a single and usually non-representative night.

Even home sleep studies are quite cumbersome and costly, and since they are limited to a single night recording, their results do not reflect the natural sleep pattern of a person. Such studies are increasingly used to diagnose sleep related breathing disorders; however, they do not allow to assess sleep time and needs, sleep quality over time, frequency of difficulties falling asleep or of night-time waking, sleep wake rhythms and cycles. Most people who suffer because of poor sleep, either being aware of it or not, are so used to it that they are not able to understand why they feel lousy during the day. These people do not get the chance to understand what their sleep problems might be.

There is therefore a great need for patient friendly, accurate, cost effective testing. This will allow sleep assessment for multiple nights, reaching a better understanding of sleep schedule and patterns across time periods, evaluation of the inner sleep structure, detection of abnormalities and disorders, all those in order to be able to alleviate problems by recommending a suitable management for the detected problems.

The solution: get to know sleep by heart

The physiological interconnections between the central nervous system and the autonomic nervous system, specifically autonomic cardiovascular control (at the sinus node level – the natural built-in cardiac pacemaker) allow the uncovering of information concerning sleep structure based on noninvasive analysis of the heart rate variability, as detected from the electrocardiogram. Moreover, morphological changes in the cardiac electrical complex occur during respiratory cycles and body position changes. The subtle changes in the electrical signal can now be quantified to  produce a sound respiratory signal and body position data. Power spectral analysis of instantaneous heart rate fluctuations reveals three components: high frequency, low frequency, and very low frequency, which are correlates of autonomic nervous system function. Novel techniques of time frequency decomposition of these fluctuations allow quantitative evaluation of transient physiological phenomena as they occur during sleep or wakefulness. These components display differential profiles in the different sleep stages, allowing for classification of sleep stages from the electrocardiogram. Based on these simple and well-known facts, we are employing a sophisticated algorithm, the HC1000P from Hypnocore Ltd., which permits conducting a sleep study based on a single ECG channel. Data recorded from this channel can be automatically scored to obtain information on sleep architecture and efficiency, arousals, autonomic nervous function and respiratory function during sleep. The addition of noninvasive monitoring of oxygen blood saturation made it possible to diagnose very accurately and reliably Obstructive Sleep Apnea. Thus the HC1000P provides a powerful new tool for evaluation of sleep in general, and sleep apnea diagnosis in particular. The performance of this new software has been clinically validated. The software is already used.

Subjective Measures of Sleepiness

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Two standard tests are used frequently to assess degrees of sleepiness.

Stanford Sleepiness Scale (SSS)

In 1973 sleep scientists at Stanford University developed a subjective measure of alertness called the Stanford Sleepiness Scale. Individuals rate themselves according to one of several statements that most closely describes their level of alertness or sleepiness.

To collect a spectrum of sleepiness indicators across a day, the SSS is administered at two-hour intervals, usually during the waking part of the day. To correlate objective measures and subjective feelings of sleepiness, the SSS may also be administered immediately before and after naps during a multiple sleep latency test.

The SSS uses the following numeric scale:

1:  Feeling active, vital, alert, and wide awake.
2:  Functioning at a high level, but not at peak performance. Able to concentrate.
3:  Relaxed and awake, but not fully alert. Still responsive.
4:  Feeling a little foggy and let down.
5:  Foggy and beginning to lose track of things. Difficult to stay awake.
6:  Sleepy and prefer to lie down. Woozy.
7:  Almost in reverie and cannot stay awake. Sleep onset is imminent.

Epworth Sleepiness Scale (ESS)

The ESS is a short questionnaire that measures daytime sleepiness and is useful for the detection of sleep disorders. It was introduced in 1991 at the Epworth Hospital in Melbourne, Australia. The ESS asks for subjects to rate (on a scale of 0 to 3) their  propensity to fall asleep in eight different situations.

The questionnaire is below.

The following questions refer to sleepiness or the tendency to doze off when relaxed.

How likely are you to doze off or fall asleep in the following situations, in contrast to just feeling tired? This refers to your usual way of life in recent times. Even if you haven’t done some of these things recently, try to work out how they would have affected you.

Use the following scale to choose the most appropriate number for each situation:

0 = would never doze
1 = slight chance of dozing
2 = moderate chance of dozing
3 = high chance of dozing

Use the following scale to choose the most appropriate number for each situation:

Situation  Chance of Dozing
1. Sitting and reading…………………
2. Watching TV…………………
3. Sitting, inactive in a public place (e.g., theatre or a meeting)…………………
4. As a passenger in a car for an hour without a break…………………
5. Lying down to rest in the afternoon when circumstances permit…………………
6. Sitting and talking to someone…………………
7. Sitting quietly after a lunch without alcohol…………………
8. In a car, while stopped for a few minutes in traffic…………………

After completion of the questionnaire, the scores are added together, and the number is assessed on a range to determine the possibility of a sleep disorder.

The Purpose of Sleep

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Sleep is both universal and fascinating. Although we spend a third of our lives sleeping, scientists don’t fully understand its nature and purpose. The most precise definition available at this time is descriptive: Sleep is a natural behavioral state (another is wakefulness) governed by the nervous system that is characterized by perceptual disengagement and motor inactivity. The state is cyclical and reversible without intervention. Unlike a coma – a total lack of consciousness – sleep is actually a semi-conscious state. This means that a minimal level of environmental awareness allows an individual to react to certain triggers. For example, a sleeping mother will hear her crying baby; people wake up when hearing their name called, or when danger such as a fire or an attack is present or imminent.

We know that sleep has a restorative function and has a major impact on physical health, cognitive performance and mood stability. It clearly is as important as air, food and water for sustaining life. Resting while awake is not a substitute for sleep.

Sleep is a dynamic process with an active brain that changes its state many times each night during different stages of sleep and through sleep cycles.

Most animals sleep, but timing and duration vary tremendously across species. We’re not sure why.

Why Do We Need to Sleep?

Here’s the most simplistic answer: We need to sleep to avoid feeling sleepy.

Researchers have illustrated this need with a simple experiment that shows the impact of sleep debt. When healthy people are forced to stay awake continuously for one or two days, their waking state is eventually interrupted, involuntarily, by short episodes of sleep. Test subjects are incapable of avoiding them. Moreover, other adverse consequences can be observed at the same time:

  • declining cognitive performance
  • disrupted biological rhythms
  • undesirable metabolic changes (e.g., hormone levels)
  • Scientists have observed, over longer periods of time, that a chronic lack of sleep
  • may cause weight gain
  • adversely impacts learning and memory
  • reduces immunity
  • shortens life span

Sleep deprivation is a major public health concern in many countries. One example everyone knows about: accidents caused by sleepy drivers.

On the other hand, quality sleep replenishes the body and mind in several ways. For example, sleep plays a crucial role in children’s growth and development. That’s a reason why young ones need more sleep than adults. Memory consolidation occurs during sleep. Body reserves and energy levels are restored while sleeping.

Interestingly, too much sleep is just as bad as too little sleep.

How much sleep someone needs is difficult to answer precisely, though statistically, a majority of people need 7½ to 8 hours

Tips for Talking to Your Doctor

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What should I say to my doctor when I sleep poorly or can’t sleep at all?

Do your best to be concise and clear. State, in succinct terms, how you perceive the problem. For example:

  • “It takes me a very long time to fall asleep.”
  • “I wake up frequently during the night.”
  • “I have trouble waking up in the morning after a sleepless night.”

You may want to ask if your problem could be related to other health issues or to medication you may be taking.

Don’t ask for sleeping pills. Instead, ask if you should consult a sleep specialist or go to a sleep clinic. If your doctor has cost information about these options, ask for it.

Finally, ask for your doctor’s recommendations about how to proceed.

Your doctor will probably ask about your usual sleep-wake schedule, including details about when you go to bed, how long it takes to fall asleep, when you wake up in the morning and whether you take naps during the day. In addition, you may be asked about these factors:

  • sleep environment characteristics
  • your preoccupation with your sleep complaints
  • snoring
  • movement during sleep
  • caffeine and alcohol consumption
  • type of job and work schedule
  • overall health
  • nutrition
  • exercise
  • daytime sleepiness
  • your mood

Based on this information, your doctor will recommend a treatment or a further workup, which may include seeing a specialist.

Total Sleep Time

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Total Sleep Time (TST)

Total Sleep Time (TST) represents the entire time spent sleeping and is the sum of the Deep Sleep Duration, Light Sleep Duration and REM Sleep Duration. TST and relative durations of DS, LS and REM are age dependent.

TST is an extremely important factor that influences well-being, physical and cognitive performance and daytime sleepiness. Many of us feel sleepy during the day just because of insufficient sleep. Sleep debt represents an ever-growing epidemic in the Western, modern society.


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