Physiological basis of sleep


Sleep disorders

By : Dr. Alireza Safaeian

Occupational Medicine Specialist

Physiological basis of sleep

Definition :sleep is a behavioral terms as a normal, recurring, reversible state of loss of the ability to perceive and respond to the external environment.

Physiological basis of sleep

• Sleep stage and cycles:

NREM (stage 1-4)


• A night’s sleep in adult :4-6 cycles

• Each cycles :about 90 min

Physiological basis of sleep

Physiological basis of sleep

Physiological basis of sleep

EEG wave frequencies:

• Beta: 14-30 Hz ( during wakefulness & drowsiness or in sleep with sedative-hypnotic)

• Alpha: 8-13 Hz

(during quiet alertness with eye closed)

• Theta: 4-8 Hz

(the most common sleep frequency)

• Delta: < 4 Hz

(20-25% in stage 3 & >50% in stage 4)

Physiological basis of sleep

Wakefulness with closed eyes

• More than 50% of epoch is alpha waves

Physiological basis of sleep

NREM synchronized, rhythmic EEG activity, partial relaxation of voluntary muscles and reduced cerebral blood flow, heart rate, blood pressure and respiratory tidal volume fall.

Physiological basis of sleep

NREM (stage 1)

Disappearance of alpha rhythm and replacement by theta waves, sharply V wave and POSTS(positive occipital sharp transient of sleep)

 slow horizontal rolling eye movement.

Physiological basis of sleep

NREM (stage 2)

K-complexes (high amplitude, biphasic waves , at least

0.5 s)

Sleep spindles (chains of rhythmic 12-14 Hz activity with duration of 0.5 to 2-3 S)

Physiological basis of sleep

NREM (stage 3 – 4)

Slow waves sleep

High amplitude(>75 mic V) delta with frequency of

2 Hz or less.

Physiological basis of sleep

REM sleep

• The state of internal arousal

• Classified as tonic and phasic

• Poikilothermia

• Dreaming

• 90-120 min after sleep onset (20-25% of sleep)

Physiological basis of sleep

REM sleep

• Low amplitude, mixed frequency theta waves mixed with alpha waves.

• Rapid eye movement

• Lowest tone in EMG



Variable monitoring during PSG




EMG (sub mental & ant. Tibial)

Respiratory airflow respiratory effort oxyhemoglobin saturation upper airway sound




Quantitative measures of sleepiness and alertness

• Sleepiness scale

Epworth sleepiness scale

Standford sleepiness scale

Visual analog scale

• Multiple sleep latency test (MSLT)

• Maintenance of wakefulness test (MWT)

• Pupillometry

• Performance test

يگتسخ ساسحا طقف هكنيا هن (

Epworth Sleepiness Scale

؟ دينزب ترچ اي و ديورب باوخ هب هك دراد لامتحا ردقچ ، ريز ياهتيعقوم رد يريگ رارق تروص رد

دينك يعس، ديا هدادن ماج نا ًاريخا اردراوم نيازا يضعبرگا يتح .

تسارضاح لاحرد امش يگدنز شور هب طوبرم تمسق نيا ) دينكب

منز يم ترچ تاقوا بلغا

؟ تشاذگ دهاوخ امش يور يرثا هچ يتلااح نينچ هك ديبايرد ، هباشم ياهراك هب هجوتاب

ندرك هعلاطم و نتسشن 1 -

3 منز يم ترچ ًلاومعم 2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

نويزيولت ياشامت

0 -

2 -

منز يم ترچ تاقوا بلغا

منز يم ترچ تاقوا بلغا

منز يم ترچ تاقوا بلغا

3 منز يم ترچ ًلاومعم

3 منز يم ترچ ًلاومعم -

2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

ندرك تبحص يسكاب و نتسشن

2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

3 منز يم ترچ ًلاومعم 2

نتسشن يطيحم رد مارآ ، راهان زا دعب

منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

) ينارنخس ةسلج اي امنيس ( نتسشن يمومع ناكم كي رد تيلاعف نودب

منز يم ترچ تاقوا بلغا 3 منز يم ترچ ًلاومعم 2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره


ديشاب فقوت نودب تعاسكي هكيروط هب ليبموتا كي رد رفاسم ناونع هب

منز يم ترچ تاقوا بلغا

) ديشاب هتش

3 منز يم ترچ ًلاومعم 2 منزب ترچ هك دراد يمك لامتحا

اد ار راك نيا ةزاجا و هدوب بسانم طيحم هكيروط هب

1 منز يمن ترچزگره

( تحارتسا يارب نديشك زارد رهظ زا دعب

منز يم ترچ تاقوا بلغا 3 منز يم ترچ ًلاومعم 2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

تسا فقوتم كيفارت رد يقياقد يارب هك يماگنه هيلقن ةليسو كي رد

منز يم ترچ تاقوا بلغا 3 منز يم ترچ ًلاومعم 2 منزب ترچ هك دراد يمك لامتحا 1 منز يمن ترچزگره

0 -

3 -

0 -

4 -

0 -

5 -

0 -

0 -

8 -

0 -

6 -

0 -

7 -

زايتما و هدش هدز عمج مه اب تلااؤس زا هدما تسدب زايتما نازيم .

تسا هدش صخشم خساپ ره رانك رد لاؤس ره زا درف زايتما نازيم


ددرگيم صخشم يياهن

Epworth sleepiness scale (ESS)

• The commonest scale to assess sleepiness

• ESS correlates with the intensity of psychological symptoms

• Higher in woman than man

• Useful for monitoring of response to treatment

• Upper normal limit = 10-11 points

• Excessive daytime sleepiness = ESS> 13

Multiple Sleep Latency Test

• The objective assessment of sleepiness and alertness (tendency to fall asleep)

• MSLT often contribute to diagnosis but is usually not sufficient .

• MSLT can help to determine the clinical significance of sleep disorder or to assess response to treatment .

• MSLT is not valid in children (<8 y)


Pre test conditions:

• A nocturnal PSG is preceded.

• The test is sensitive to sleep deprivation so adequate total sleep for a week is needed (actigraphy is useful)

• Sleep log (diary) of amount and pattern of sleep during 2weeks before MSLT

• Physical exercise not be performed on the day of test

• No smoking and caffeine for at least 30 min before test


• Drug such as stimulants, hypnotics, major tranquillizers, opioids should be discontinued at least

2 weeks

• Fluoxetine (long half life) should be stopped earlier.

• If stopping is impossible it is better not to perform

MSLT at all. (not interpretable)

• Heavy caffeine use should be slowly weaned a week before test.

• Urine drug screen should be obtain.


Performance of the MSLT

• The patient is given 4-5 nap opportunities (20 min) to sleep over the day, usually at 2 hours intervals

(8am-10am-12 noon-2pm-4pm)

• The patient lies in bed in a dark quiet room with comfortable cloths and no shoes.


Standard terms:

• Sleep latency: the time from light out to the first epoch of any stage of sleep (max= 20 min)

• REM latency: the time from first sleep to the first epoch of REM sleep (max= 15 min)

• Mean sleep latency: average of sleep latencies


Interpretation of SMLT:

• Normal MSLT= mean sleep latency >15 min and

0-1 REM sleep

• Mild sleepiness = mean sleep latency of 10-15 min

• Moderate Sleepiness= mean sleep latency of 5-10 min

• Severe (pathologic) sleepiness= mean sleep latency

<5 min


Patient Name:





Start Time

End Time

Recording Length

Total Sleep Time

Onset to Sleep

Onset to REM Sleep



Stage 1

Stage 2

Stage 3

Stage 4



Mosleh, Sadegh




81 Kg.

Nap 1








Nap 2




No Sleep






Study Date:

Subject Code:

Nap 3








Nap 4








178 Cm.




Nap 5

No Nap

No Nap

No Nap

No Nap

No Nap

No Nap








Maintenance of Wakefulness Test


• The patient is asked to remain awake as long as possible.

• MWT is not diagnostic test for degree of sleepiness but rather a test of ability to remain awake


MWT is used:

1) To assess fitness to fly a plane or drive a truck or bus.

2) To assess a pilots permission to regain their license before treating for sleep apnea


(by United State Federal Aviation Administration)

3) To assess efficacy of treatment for hypersomnia.

4) To assess narcoleptic patient who complain of tiredness, despite of high quantities of stimulant medication.


Performance of MWT

• Nocturnal PSG before MWT is optional.

• Four trials at 2 hours intervals to remain awake with eye open.

• The patient is sitting semireclining in bed, with back and head supported by a bed rest cushion.

• A night-light (7.5 W) behind the patient head.

• Two variant of test: 20 min & 40 min


Interpretation of MWT:

• Mean MWT latencies do not correlate with total sleep time (sleep deprivation does not affect the result)

• The cut-off point for alertness in 20 min version is 11 min & in 40 min version is 22.5 min (15 percentile)


• A small devices as like as wristwatch.

• It is worn during both the night and day.


Sleep and Performance

• Sustained behavioral wakefulness (90 hours) resulted in:

• decreased : sensory acuity reaction time motor speed memory

• occurrence of uncontrollable napping and semi-wake dream

sleepiness is modulated by :

A circadian rhythm

The stronger nadir occurs at night, between 10 P.M. and 8 A.M., peaking around 4 A.M.

The second occurs between 2 P.M. and 4 P.M.

The longer we have been awake (the fewer hours we have slept), the more our drive for sleep increases


Sleep disorders - overview

There are more than 100 different sleeping and waking disorders. They can be grouped into four main categories:

• Problems falling and staying asleep (insomnia)

• Problems staying awake (excessive daytime sleepiness)

• Problems sticking to a regular sleep schedule (sleep rhythm problem)

• Unusual behaviors during sleep (sleep-disruptive behaviors)

Sleep disorders - classification

1) Dyssomnias :difficulty to get to sleep, or to remain sleeping.

2) Parasomnias : abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep

3) Medical or psychiatric conditions that may produce sleep disorders

4) Sleeping sickness : a parasitic disease which can be transmitted by the Tsetse fly.



• Defined as the subjective sense that sleep is difficult to initiate or maintain or that sleep itself is non refreshing.

• About one third of the adult population experiences insomnia (nearly 10% as a chronic problem)

• They sufferer from daytime consequences similar to those associated with chronic sleep deprivation, such as fatigue, performance decrements, and mood disturbances .

Insomnia (Pathophysiology)

Precipitating factor (5 Ps):

• Physical

• Psychological

• Psychiatric

• Pharmacologic

• Physiologic

Insomnia (Diagnosis)

NOTE Insomnia is a symptom and not a disorder itself

• Careful evaluation of potential underlying causes or contributors

• The principal diagnostic tools are subjective assessment of sleep quantity and quality. (Diaries of sleep-wake activity)

• Objective sleep-monitoring technology: polysomnography & actigraphy (a wrist-worn motion detector)

Insomnia (Treatment)

• You should seek help if your insomnia has become a pattern, or if you often feel fatigued or unrefreshed during the day and it interferes with your daily life.

Insomnia (Treatment)

General :

• Correction of the underlying cause (medical or psychiatric issues).

• Simple changes in routine, living situation, and food intake

• Education of mechanics of sleep (sleep promoting and interfering behaviors- Relaxation training, stimulus control, sleep restriction, and cognitive behavioral therapy are some examples.)

Insomnia (Treatment)



Transient insomnia (a few days to a couple of weeks) : sedatives/hypnotics like shorter acting benzodiazepines, non benzodiazepine receptor agonists, and the new melatonin receptor agonists

Short-term insomnia (several weeks to a month): sedative/hypnotic therapy for the short term, behavioral therapies and education

Long-term or chronic insomnia (months to years):

- behavioral treatments such as sleep restriction, cognitive therapy, relaxation therapies, stimulus control, and biofeedback (effective during a 6-8 week program)

-Sedative/hypnotic medication as reinforcement

Insomnia (Treatment)

• Over 40% of people with complaints of insomnia have been reported to self-medicate with over-the-counter products and/or alcohol

• Alcohol has sedating nature but it causes fragmented sleep and profound REM sleep rebound and nightmares and rapid tolerance

• Natural products, such as L-tryptophan, melatonin and valerian root

Obstructive Sleep Apnea

Obstructive Sleep Apnea

• The most common disorder resulting in daytime sleepiness among adult workers

• OSAS is characterized by repetitive brief periods (10 to 60 S) of cessation of airflow during sleep, which result in brief arousals.

• The subtle form of OSAS is upper airway resistance syndrome (UARS)

• Daytime consequences include excessive sleepiness, cardiovascular changes, and cognitive deficits

OSAS (Pathophysiology)

Blockage of the upper airway is result of:

• Changes in muscle tone

• Redundant tissue

• Enlarged tonsils and adenoids

• Anatomically small airway passage

• Changes in the arousal threshold occurring with the ingestion of alcohol or sedating drugs.

OSAS (Symptoms)

• Typical symptoms of untreated OSAS and UARS include loud, sporadic snoring, excessive sleepiness, and restless sleep.

• Consequences: Cardiovascular (hypertension, arrhythmia, and strokes) loss of memory, irritability, depression, and impotence.

OSAS (Treatment)

Continuous positive airways pressure device (CPAP)

• Surgical repairs of the upper airway uvulopalatopharyngoplasty (UPPP)

• Laser-assisted UPPP (LAUP)

• Dental devices designed to increase airway space by extending the mandible

• Behavioral techniques such as weight loss or position changes during sleep



• Debilitating lifelong CNS disorder of excessive daytime sleepiness affecting 0.03% to 0.05% of the worldwide population

• Onset peaking in the second decade but continuing into the fifth decade of life


Pentad of primary symptoms (not all must be present for diagnosis).

• severe sleepiness (all persons)

Cataplexy (65% to 90%)

• hypnagogic hallucinations (30% to 60%)

• sleep paralysis (30% to 60%)

• fragmented nocturnal sleep (50% )

Narcolepsy (Pathophysiology)

• An autoimmune process that attacks the hypocretin (orexin) system in the hypothalamus.

• A strong association with HLA class II

• Strong genetic involvement (not conclusive or necessary for the diagnosis of narcolepsy)

Narcolepsy (Diagnosis)

• Nocturnal polysomnograms followed by a Multiple

Sleep Latency Testing (MSLT)

• Positive MSLT

, after a night in which other sleep disorders are excluded, requires a mean latency to sleep of under 8 minutes with at least two REM-onset naps

• Although cataplexy may be a pathognomonic but polysomnography is necessary.

• Currently, hypocretin-1 levels of cerebral spinal fluid

Narcolepsy (Treatment)

 Treatment is very individualized and depends on the clinician's expectations for outcome as well as the patient's and family's goals

Therapy involves the combination of pharmacologic and behavioral techniques

Short (20 minutes) daytime naps.Regular sleep hours and daytime schedules

Antidepressant drugs (TCA and SSRI), improve the REM sleep related symptoms of cataplexy, hallucinations, and sleep paralysis

 gamma-hydroxybutyrate (sodium oxybate) for cataplexy. and daytime sleepiness

Shift-work Sleep Disorder

• SWSD is characterized by complaints of insomnia or excessive sleepiness related to work hours scheduled during normal sleep periods and occurs despite optimizing the sleep environment.

• The FDA has recently approved modafinil

(Provigil) for use as a wake promoter in this disorder

Impact of


on the Workplace

Decrease peak performance at positions that require heightened vigilance for long time.

The concerned about the impact of hypnotic therapy and any sedating effects.

Any sleep loss may impact the general health of the worker through changes caused to immune function and the stress response.

Impact of


on the Workplace

The global impact of narcolepsy on the workplace will depend, on the person's age at symptom onset and diagnosis

Certain jobs for which a person with narcolepsy is unfit.

1-occupations requiring long periods of driving

2-monotonous attention to critical dials and gauges

If cataplexy is uncontrolled, occupations that offer episodes of intense emotional excitement should be avoided

Impact of OSAS on the Workplace

• The impact of untreated OSAS on the workplace can be serious due to the effects of unrecognized sleep loss

• High risk job :commercial driver who is male, middle aged, and overweight/obese

Sleep hygiene

1. Power Down

• The soft blue glow from a cell phone, tablet, or digital clock on your bedside table may hurt your sleep.

• Tip: Turn off TVs, computers, and other blue-light sources an hour before you go to bed. Cover any displays you can't shut off.

2. Nix Naps

• You’ll rest better at night. But if you have to snooze while the sun's up, keep it to 20 minutes or less. Nap in the early part of the day.

• Tip: Overcome an afternoon energy slump with a short walk, a glass of ice water, or a phone call with a friend.

3. Block Your Clock

• Do you glance at it several times a night? That can make your mind race with thoughts about the day to come, which can keep you awake .

• Tip: Put your alarm clock in a drawer, under your bed, or turn it away from view.

4. Try a Leg Pillow for Back Pain

• Your lower back may not hurt enough to wake you up, but mild pain can disturb the deep, restful stages of sleep. Put a pillow between your legs to align your hips better and stress your low back less.

• Tip: Do you sleep on your back? Tuck a pillow under your knees to ease pain.

5. Put Your Neck in 'Neutral'

• Blame your pillow if you wake up tired with a stiff neck. It should be just the right size -- not too fat and not too flat

-- to support the natural curve of your neck when you're resting on your back. Do you sleep on your side? Line your nose up with the center of your body. Don’t snooze on your stomach. It twists your neck.

• Tip: Use good posture before bed, too. Don't crane your neck to watch TV.

6. Seal Your Mattress

• Sneezes, sniffles, and itchiness from allergies can lead to lousy shut-eye. Your mattress may hold the cause.

Over time, it can fill with mold, dust mite droppings, and other allergy triggers. Seal your mattress, box springs, and pillows to avoid them.

• Tip: Air-tight, plastic, dust-proof covers work best.

7. Save Your Bed for Sleep

• Your bedroom should feel relaxing. Don’t sit in bed and work, surf the Internet, or watch TV.

• Tip: The best sleep temperature for most people is between 20-22 degrees.

8. Set Your Body Clock

• Go to sleep and wake up at roughly the same time every day, even on weekends. This routine will get your brain and body used to being on a healthy snooze-wake schedule. In time, you'll be able to nod off quickly and rest soundly through the night.

• Tip : Get out in bright light for 5 to 30 minutes as soon as you get out of bed. Light tells your body to get going!

9. Look for Hidden Caffeine

• Coffee in the morning is fine for most people. But as soon as the clock strikes noon, avoid caffeine in foods and drinks. Even small amounts found in chocolate can affect your Zzzz's later that night.

• Tip: Read labels. Some pain relievers and weight loss pills contain caffeine.

10. Work Out Wisely

• Regular exercise helps you sleep better -- as long as you don’t get it in too close to bedtime. A post-workout burst of energy can keep you awake. Aim to finish any vigorous exercise 3 to 4 hours before you head to bed.

• Tip : Gentle mind-body exercises, like yoga or tai chi, are great to do just before you hit the sack.

11. Eat Right at Night

• Don’t eat heavy foods and big meals too late. They overload your digestive system, which affects how well you sleep. Have a light evening snack of cereal with milk or crackers and cheese instead.

• Tip: Finish eating at least an hour before bed.

12. Rethink Your Drink

• Alcohol can make you sleepy at bedtime, but beware.

After its initial effects wear off, it will make you wake up more often overnight.

• Tip: Warm milk or chamomile tea are better choices.

13. Watch What Time You Sip

• Want to lower your odds of needing nighttime trips to the bathroom? Don’t drink anything in the last 2 hours before bed. If you have to get up at night, it can be hard to get back to sleep quickly.

• Tip: Keep a nightlight in the bathroom to minimize bright light.

14. Lower the Lights

• Dim them around your home 2 to 3 hours before bedtime. Lower light levels signal your brain to make melatonin, the hormone that brings on sleep.

• Tip: Use a 15-watt bulb if you read in the last hour before bed.

15. Hush Noise

• Faucet drips, nearby traffic, or a loud dog can chip away at your sleep. And if you're a parent, you might be all too aware of noises at night long after your children have outgrown their cribs.

• Tip: Use a fan, an air-conditioner, or a white noise app or machine. You can also try ear plugs.

16. Turn Down Tobacco

• Nicotine is a stimulant, just like caffeine. Tobacco can keep you from falling asleep and make insomnia worse.

• Tip: Many people try several times before they kick the habit. Ask your doctor for help.

17. Beds Are for People

• A cat's or a dog's night moves can cut your sleep short. They can also bring allergy triggers like fleas, fur, dander, and pollen into your bed.

• Tip : Ask your vet or animal trainer how you can teach your pet to snooze happily in its own bed.

18. Free Your Mind

• Put aside any work, touchy discussions, or complicated decisions 2 to 3 hours before bed. It takes time to turn off the "noise" of the day.

If you’ve still got a lot on your mind, jot it down and let go for the night. Then, about an hour before you hit the sack, read something calming, meditate, listen to quiet music, or take a warm bath.

• Tip: Even 10 minutes of relaxation makes a difference.

19. Use Caution with Sleeping Pills

• Some sleep medicines can become habit-forming, and they may have side effects. Ideally, pills should be a short-term solution while you make lifestyle changes for better Zzzz's. Ask your doctor what’s OK.

20. Know When to See Your Doctor

• Let her know if your sleeplessness lasts for a month or more. She can check to see if a health condition -- such as acid reflux, arthritis, asthma, or depression -- or a medicine you take is part of the problem.

Thanks for your attention