Tag : sleep-wake cycle

The Science of Sleep – Know What Defines Your Sleep

How can you tell if you’re sleeping enough? And are you suffering from Fatigue, or Sleepiness? And what is the difference, if any? Fatigue or extreme tiredness, exhaustion and weariness may be a secondary or direct consequence of sleep loss or sleep deprivation which is easily identified in constant sleepiness better known as Excessive Daytime Sleepiness.

(EEG Image courtesy of en.wikipedia.org)

(EEG Image courtesy of en.wikipedia.org)

Measuring Sleep Patterns

Physiological analysis of your sleep using EEG Electro-encephalography, EOG Electro-oculography, and EMG Electro-myography further depict your sleep as having two key individual stages:

  1. the NREM stage (Non Rapid Eye Movement) and,
  2. the REM stage (Rapid Eye Movement).

These two sleep stages operate cyclically in alternating turns; they are independently controlled, and therefore function independently as well.

 

REM NREM Image Courtesy of faculty.washington.edu

(REM NREM Image Courtesy of faculty.washington.edu )

Read our review of the Top 10 Best Adjustable Beds and see if that can help regularize your sleeping cycle.

In adult humans, their sleeping cycle exhibits 4 to 6 cycles, each of which averages anything from 110 to 90 minutes. NREM stage dominates about 75-80% of the total sleeping time and has 3 more sub-levels (N1, N2 and N3) , while the REM stage takes up about 20-25% of the total sleeping time and dominates the last third portion of the sleep (slow-wave sleep accounts for most of the first third of the sleeping time).

REM sleep in infant newborn babies takes up about 50% of the sleep. This however changes by the time they get to 6 years old when their REM sleep reduces to the normal average REM sleep of an adult which takes up about 25% of the sleep. It only takes about 3 months for a newborn baby to achieve the NREM/REM sleep cycling patterns of adult’s sleep.

Accordingly, the progression of sleep states goes from the wakeful state, to the onset of the sleeping state, which graduates to NREM sleep stage and finally the REM sleep stage.

 

( Sleep NREM and REM - Image Courtesy of www.habitot.org )

( Sleep NREM and REM – Image Courtesy of www.habitot.org )

 

The EEG is most instrumental in understanding sleep disorders. EEG also helps in observing and analyzing the two main stages of sleep, NREM and REM, nonetheless, the EMG and EOG are equally important in sleep analysis. Some of the key observations made include:

 

( EEG of NREM sleep and REM sleep - Image Courtesy of cnx.org )

( EEG of NREM sleep and REM sleep – Image Courtesy of cnx.org )

 

(For the REM – Rapid Eye Movement stage)

  • REM sleep consists of rapid rhythms, rapid EEG activity at low voltage
  • REM brainwaves are Theta waves,
  • REM waves have a saw-tooth plotting
  • REM bears rapid eye movements that are multi-directional
  • REM indicates diminished muscle activity within the chin area via an EMG
  • REM presents phased vacillation in the cardiac activity and blood pressure
  • REM features phased tongue motions
  • REM elicits irregular rates of respiration
  • REM sleep is absent of muscle tone contractions
  • REM sleep also highlights even lower responsiveness to external stimulation
( Sleep Spindles and K-Complexes Image Courtesy of en.wikipedia.org )

( Sleep Spindles and K-Complexes Image Courtesy of  en.wikipedia.org )

(For the NREM – None Rapid Eye Movement stage)

  • NREM is represented by progression into a state of diminished responsiveness to external or environmental stimuli;
  • NREM is characterized by slow movements of the eyes (unlike REM which has rapid eye movements)
  • NREM shows via EEG slow brainwave activity
  • NREM plotting shows waveforms with K complexes and spindles
  • NREM typically bears minimal muscle contractions and movements
(EEG of REM sleep and NREM sleep - Image Courtesy of commons.wikimedia.org)

(EEG of REM sleep and NREM sleep – Image Courtesy of  commons.wikimedia.org)

 

Your Sleep Requirements by Age

The amount of sleep required varies progressively with age, from the fetus, to the infant, early childhood to teenage years and finally adulthood and senior years. Sleep requirements also depend on the growth, development and maturation state of the CNS (Central Nervous System). Certain other factors are bound to affect the changes in sleep patterns and these include: environmental aspects, neurological factors, genetic background, and any other co-morbid medical disorders of the neurological system and other body systems.

 

( Sleep Requirements - Image Courtesy of academic.pgcc.edu )

( Sleep Requirements – Image Courtesy of academic.pgcc.edu )

The bottom line remains: That one’s sleep patterns and sleeping requirements do change rather drastically from their infant years to the latter time in older age.

In newborn babies, the sleeping patterns are found to be polyphasic (meaning they need several sessions of sleeping time) whereby infants require at good 16 hours of sleeping time each day. However, this gradually decreases to about 11 hours of sleep per day as they grow older at around 3 to 5 years old. By the time they get to the pre-pubertal years of 9 to 10 years old, they only require about 10 hours of sleep per day.

Once they’ve grown into adulthood, the average requirement for adults in sleeping time is about 7 to 8 hours of sleep for a night’s sleep. Sleep in adults is monophasic meaning they only require one session of sleep (one phase, say overnight or daytime for night shift workers); this however later changes in the elderly whose sleep patterns are biphasic (which means two separate sleeping sessions, say the main sleeping time at night, plus an afternoon siesta), just like in infant babies and pre-schoolers who require biphasic sleeping sessions.

 

Circadian Rhythm of Sleep-Wake Patterns

The primary role of the Circadian Rhythm is to keep the physiological, behavioral and humoral body systems coordinated so as to modulate the sleep-wake patterns. Notably, there are two distinct and opposite components:

1. The homeostatic desire to sleep
2. The circadian rhythm of arousal

( Sleep Urge and Circadian Rhythm - Image Courtesy of rebrn.com )

( Sleep Urge and Circadian Rhythm – Image Courtesy of rebrn.com )

 

To distinguish these two key components:
>> In the precedence homeostatic drive, the person experiences an increased need for sleep (a propensity or inclination to sleep) which is indicated by sleepiness; it comes after a prolonged period of being in the wakeful state.

>> In the precedence of the circadian rhythm, the person experiences alternations in the alertness of their physiological processes and this affects various aspects of their sleepiness or need for sleep (including the duration of sleep, timing of sleep, among other factors); these changes are experienced as they occur depending on the time of the day as they are cyclical alternations.

 

( SCN - Image Courtesy of en.wikipedia.org )

( SCN – Image Courtesy of  en.wikipedia.org )

 

When one wakes up in the morning after coming from deep sleep overnight, the body’s homeostatic desire for sleep is pretty much null; and the output of the SCN (Supra Chiasmatic Nuclei) is low. This may be seen by recording the firing rates of the intra-cerebral neurons.

 

( Circadian Rhythm and Sleep Homeostasis - Image Courtesy of www.medscape.org )

( Circadian Rhythm and Sleep Homeostasis – Image Courtesy of  www.medscape.org )

 

Gradually, with the progression of the day (during daytime), the homeostatic desire for sleep is seen to gain with time; and this is further counteracted by an increased output of the SCN. Towards the onset of the dusk as the day ends, the output of the SCN is however seen to diminish as the homeostatic desire which is at its peak leads to the onset of the sleeping state.

Early at dawn (during daybreak), the homeostatic desire for sleep is little to none, while the circadian rhythm is seen to take charge causing arousal that triggers one to wake up, and thus beckoning the onset of a wakeful state.

 

 

(Sleep and Sleeping Disorders - Image Courtesy of en.paperblog.com )

Sleep Disorders – Know What’s Killing Your Sleep

 

You may have noticed that you’re more likely to feel sleepy at certain times of the day… Scientifically, there are two time periods when you’re very likely to feel sleepy and thus most vulnerable to falling asleep, and they are: the period from 2:00 AM to 6:00 AM; and the period from 2:00 PM to 6:00 PM. It is further noted that the earlier time capsule in the early morning hours (2:00 – 6:00 AM) bears a much stronger desire to sleep than the latter one in the afternoon.

 

( Drowsy Driving Graph - Image Courtesy of www.cdc.gov )

( Drowsy Driving Graph – Image Courtesy of www.cdc.gov )

 

It therefore comes as no surprise that the greatest incidence of accidents due to sleepiness are found to occur at this very same time period in the early morning hours.

 

( Time of Road Accident Occurrence - Drowsy Driving - Image Courtesy of www.nhtsa.gov )

( Time of Road Accident Occurrence – Drowsy Driving – Image Courtesy of www.nhtsa.gov )

READ: What’s the best memory foam mattress type to prevent sleep disorders?

Biological Factors Affecting Your Sleep

Aside from the homeostatic condition and circadian rhythm factors that contribute to sleep patterns in humans, certain other factors like proteins (called Cytokines, produced by Leukocytes) among other cells that act as mediators in the intra-cerebral cells also have a key role in the regulation of both sleep and immunity. Particularly, the Cytokines have a great impact on the pathogenesis and incidence of EDSExcessive Daytime Sleepiness which is associated with sleep deprivation and various sleep disorders.

 

Further, there are certain sleep enhancing substances otherwise known as sleep factors that promote sleep. After long periods of being in the wakeful state, or when the person is suffering from illness due to inflammation (rheumatoid arthritis, HIV) or infection (viral, bacterial), the concentration of these sleep factors increases markedly thus inducing sleep.

( Cytokines and Sleep Loss - Image Courtesy of www.researchgate.net )

( Cytokines and Sleep Loss – Image Courtesy of www.researchgate.net )

What is the Function of Sleep?

The true function of sleep is seen to be one of the greatest mysteries in science. Nonetheless, there’s no doubting the essential necessity of sleep given that sleep deprivation has been shown to result in dire consequences in both the long-term and short-term. Sleep deprivation typically results from modern lifestyles as well as sleeping disorders such as Insomnia, Sleep Apnea, neurological, psychiatric and psychological (personality) disorders, and may also be a side-effect of medication.

(Sleep Deprivation Image Courtesy of - www.lifehack.org )

(Sleep Deprivation Image Courtesy of – www.lifehack.org )

 

Short-term effects of sleep deprivation:

  • Low attention span
  • Diminished concentration
  • Lowered quality of life
  • Reduced productivity
  • Accidents and mishaps on the road, at home and other environs
  • Absenteeism from work or school

Long-term effects of sleep deprivation:

  • Obesity
  • Impaired memory
  • Depression
  • Cardiac disease (coronary artery disease, heart failure)
  • High blood pressure
  • Stroke
  • Diabetes (especially Type 2 Diabetes Mellitus)
  • Increased mortality and morbidity (due to accidents and sleep-related chronic diseases)

 

( Sleep Deprivation - Image Courtesy of healthpromotion.caltech.edu )

( Sleep Deprivation – Image Courtesy of healthpromotion.caltech.edu )

 

Undebatable is the fact that quality sleep is known to be conservative and restorative to one’s health, adaptive to one’s ideal physiological state, consolidating to one’s memory and cognitive functioning, thermoregulative in the body temperature. For instance, scientific studies have confirmed that adequate sleep before study and learning is vital to memory consolidation.

 

Prevalence of Sleep Complaints in the US population

In the final report from the National Center for Sleep Disorders Research, it was shown that over 40 million citizens of the US actually suffer from chronic sleep disorders that affect their sleep and wakeful states; the same is seen across the globe as prevalence of sleep complaints is very rampant especially with modern lifestyles and current demands. It was shown that about 35% of the US population has trouble falling asleep, or staying asleep, or waking up early in the morning, or experience non-restorative sleep. For many of them (about 10%) the insomnia persists to affect their normal functioning during the day; while millions others (3-4%) suffer from Sleep Apnea. Every 1 in 5 adults is shown to complain of Excessive Daytime Sleepiness (EDS).

 

( Sleep Deprivation - Image Courtesy www.bbc.com )

( Sleep Deprivation – Image Courtesy www.bbc.com )

 

There were 4 main sleep-related complaints that people mostly seek medical attention for, namely:

  1. Insomnia
  2. EDS – Excessive Daytime Somnolence
  3. Inability to fall asleep
  4. Abnormal behavior and movement during sleep

 

Clinical Evaluation of your Sleeping Disorder

When you seek medical attention for your suspected sleeping disorder, several factors will be assessed even before lab tests can be carried out; you will first undergo an analysis of your medical history, as well as a physical examination of your body.

Your medical history evaluation will be as detailed as possible, assessing factors such as: your sleeping habits and patterns; medical history of any medication previously or currently being taken; any underlying neurological, psychological and psychiatric disorders; whether one is using any drugs and substances like alcohol; the family history – any genetic disorders (cardiovascular, endocrinological, respiratory, neurological) and general family background.

The medical assessment of your sleeping condition will not just focus on the symptoms presented in the tight time frame at the onset of sleep or the duration of your sleeping phase, but rather, an entire analysis of the 24 hours in your day will be under the microscope. Your sleeping pattern will be evaluated based on: time of sleep onset, frequency of sleep, type of symptoms presented and at what time.

 

( Pediatric PSG - Image Courtesy of en.wikipedia.org )

( Pediatric PSG Testing – Image Courtesy of en.wikipedia.org )

 

Some of the common symptoms typically assessed occur in the early evening (at night), or at various stages of sleep and they include:

  • RLS – Restless Leg Syndrome
  • Leg jerking during the night
  • RBD – REM Behavior Disorder
  • Abnormal NREM behavior and movements
  • Transition disorders of the Sleep-Wake cycle
  • Arousal disorders
  • Snoring
  • Repetitive awakening (sleep disruption)
  • Breathing disorders during one’s sleep (e.g. Breathing cessation while asleep)
  • Constant inevitable desire to fall asleep
  • Fatigue
  • Sleep walking
  • Lab Testing in Diagnosing Sleep Disorders

 

After the extensive evaluation of the patient’s medical history and their physical examination, laboratory testing follows suit. The ab testing should entail a build up of the primary sleeping condition that leads up to other secondary symptoms and conditions which are co-morbid to the sleep disorder.

There are 2 key lab tests in analyzing and testing a sleep disorder, and they are:

  • PSG – Polysomnography
  • MSLT – Multiple Sleep Latency Test

 

( PSG Test Image Courtesy of - www.chicagosleepapneasnoring.com )

( PSG Test Image Courtesy of – www.chicagosleepapneasnoring.com )

 

The PSG Test concurrently assesses several physiological aspects including: airflow in the nose, airflow in the mouth, repiratory (breathing) effort), saturation of oxygen, positioning of the body, snore analysis, EEG (Electro-Encephalography), EMG (Electro-Myography), EOG (Electro-Oculography), EKG (Electro-Cardiography).

 

(MSLT Image Courtesy of - www.medscape.org )

(MSLT Image Courtesy of – www.medscape.org )

 

Contrary to common assumptions, sleep analysis of sleep disorders is not only relevant and dynamic, but also complicated yet necessary — especially considering how important sufficient restful sleep is to your overall well-being.

 

 

Sleeping Disorders

Your Sleep and Sleeping Disorders

 

Sleep disorders may be more prevalent than how much is understood of them… With many people all over the world suffering in silence, unaware that they are actually victims of one or more of the various sleeping disorders as discussed here, it only becomes a concern when other health concerns arise to which more attention is given.

 

( Sleep-Wake Disorders - Image Courtesy of www.nationalregister.org )

( Sleep-Wake Disorders – Image Courtesy of www.nationalregister.org )

 

In classifying sleep disorders, there are 4 key sleeping complaints that commonly arise and these are:

  • Inability to Fall Asleep – Do you have trouble falling asleep when you need to sleep?
  • Insomnia – Are you sleep deprived and barely ever have a good night’s sleep?
  • Excessive Daytime Sleepiness – Do you feel drowsy and sleepy during the day even though you slept at night?
  • Sleep Behavior – Do you elicit sleep mannerisms like talking in your sleep, or sleep walking?

 

( Image Courtesy of www.forbes.com )

( Image Courtesy of www.forbes.com )

What Sleep Means…

When you fall asleep, there are measurable physiological attributes and changes that do occur, and these are visible in the electrical signals and brainwave patterns acquired during your sleep state.

The sleeping state presents itself behaviorally and physiologically and is therefore analyzed accordingly…

( Sleep in Animals - Image Courtesy of hayashi.wpi-iiis.tsukuba.ac.jp )

( Sleep in Animals – Image Courtesy of hayashi.wpi-iiis.tsukuba.ac.jp )

 

Behavioral characteristics of the Sleep State

  • Immobility – lack of movement or slight movement
  • Slowed eye movements
  • Diminished cognitive functioning
  • Characteristic sleep positions
  • Extended reaction time
  • Little to no response to environmental stimuli (external arousal)
  • Increased threshold of arousal
  • State of unconsciousness that is reversible

 

Circadian sleep disorder

( Image courtesy of chronobiology.com )

 

Physiological characteristics of the Sleep State

Indicators of the physiological aspects of sleep are analyzed using:

  • EEG – Electro-encephalography
  • EOG – Electro-oculography
  • EMG – Electro-myography

 

( Sleep Monitoring Tests - EEG - EOG - EMG - Image Courtesy of www.ima.org.il )

( Sleep Monitoring Tests – EEG – EOG – EMG – Image Courtesy of www.ima.org.il )

 

Diagnosing your sleep disorder

However easy it is to pass up a sleep disorder as an isolated sneeze in summer, the assessment and diagnosis of the sleeping disorder requires deeper and conclusive assessment of the root cause. It typically entails a thorough detailing of one’s family history with regards to health and medical welfare, psychological and psychiatric conditions, mental and neurological disorders, history of drug and substance abuse.

 

( Short Sleep Impact on Daily Life Activities and Performance - Image Courtesy of www.cdc.gov )


   ( Short Sleep Impact on Daily Life Activities and Performance – Image Courtesy of www.cdc.gov )

The rule of thumb in diagnosing sleep disorders is:

  • First and foremost, to identify the root cause of the sleep impairment and identifying if it is a symptom of yet another underlying condition
  • Then, follow up with treatment for the co-morbid health conditions associated with the sleep disorder

There are also a number of medical lab tests used in the investigation of sleep disorders, including, polysomnography (studied overnight), actigraphy, sleep latency (assessed multiple times), and assessing the maintenance of wakeful states.

 

Common Sleeping Disorders of the Modern Era

( Sleep Analysis Testing – Image courtesy of Wisegeek.com )

 

Where treatment the primary underlying medical condition does not prevail, treatment of the sleep disorder then takes precedence for the wellbeing of the patient. Usually, very little medical supervision and consultation will be necessary on the part of the sleep disturbed person once after the appropriate diagnosis has been made for their sleeping disorder. It is also highly recommended that you do see a Sleep Specialist if you suspect that you may be having a sleep condition that needs medical attention for a laser targeted approach to your sleep impairment.

Key pointers for medical practitioners in the assessment of sleep disorders include:

  • Insomnia
  • Narcolepsy-Cataplexy Syndrome
  • Parasomnia (e.g. REM Behaviour Disorder, Partial Arousal Disorder, etc)
  • Sleep Disorders of the Circadian Rhythm (e.g. Work shift disorders, Jet lag, etc.)