Normal Sleeping

Jameel Adnan, MD.Community & Primary Health CareKAAU-RABEG BRANCH

Round Map

IntroductionSleep StagesSleep ArchitectureREM Latency vs Sleep latencyChanges with ageFunction of Sleep

Introduction

Thousands of articles about sleep and sleep disorders appear each year in medical and psychological journals

>80 different sleep disorders have been described.

Despite the intensive efforts that these publications reflect, there is still no definitive explanation for why we sleep.

Introduction

Sleep is not a passive process, but rather an active state that is as complex as wakefulness.

The brain is not "at rest" during sleep; it is involved in a wide variety of activities.

Sleep Stages

Sleep Stages

Two general states: o Rapid Eye Movement sleep (REM) o Non-Rapid Eye Movement sleep (NREM).

NREM sleep is further subdivided into four NREM stages.

1. REM Sleep

1. REM Sleep

The brain is active, and the body is inactive. three main features:

1.A low voltage, fast frequency EEG pattern2.The presence of rapid eye movements3.An atonic electromyogram (EMG)

1. REM Sleep

1. A low voltage, fast frequency EEG pattern, resembles an active, awake EEG pattern. So, REM

sleep is sometime called paradoxical sleep.

2. The presence of rapid eye movements. The chances are high that the patient will report

dreaming if awakened during this period.

1. REM Sleep

3. An atonic ElectroMyoGram (EMG) o Consistent with inactivity of all voluntary muscles

except the extraocular muscleso The individual is paralyzed during REM sleep. o Result from direct inhibition of alpha motor

neurons. All three primary characteristics of REM sleep are

not always present simultaneously.

1. REM Sleep

Phasic and tonic REM sleep REM sleep consists of two different states, based

on the occurrence of rapid eye movements o Phasic REM sleep.o Tonic REM sleep.

1. REM Sleep

o REM sleep is a predominantly parasympathetic (vagal) state, but during phasic REM sleep, there are sudden bursts of sympathetic nervous system (SNS) activity associated with rapid eye movements.

o These bursts of SNS activity have been reported to be associated with sudden increases in arterial blood pressure, cardiac or cerebral ischemia (frequently in the

early morning hours) cardiac arrhythmias, and sudden changes in heart and respiratory rates .

1. REM Sleep

Short central apneas and hypopneas are also common during phasic bursts of rapid eye movements.

Long cardiac asystoles have been noted to occur in otherwise healthy young individuals during phasic bursts of REMs.

2. NREM Sleep

2. NREM Sleep

consists of 4 sleep stages defined primarily by the frequency and amplitude of the EEG• The brain is inactive, the body is active. Stage 1 sleep• It is the transition from wakefulness to deeper sleep• characterized by fast EEG frequencies in the theta range (4

to 7 Hz). • It is the lightest stage of sleep, patients awakened from

stage 1 sleep typically do not perceive that they were actually asleep.

• 2-5 % of total sleep time in young adults

NREM Sleep

Stage 2 sleep Called intermediate sleep A true physiologic stage of sleep. 40-50 % of total sleep time. is characterized by a slowing of EEG frequency and

an increase in EEG amplitude.

NREM Sleep

Two distinct features of NREM sleep appear on the EEG for the first time in this sleep stage:

o Sleep spindles. transient "spindle" shaped features of the EEG frequency of 12-14 Hz lasting at least 0.5 seconds. They are most prominent at the vertex of the scalp.

o k-complexes. These consist of a well delineated negative sharp wave immediately followed by a positive component standing out from the background EEG with a total duration ≥0.5 seconds, usually maximal in amplitude over the frontal regions.

NREM Sleep

Stages 3 and 4 sleep (combined) deep sleep or slow wave sleep, 20 % of total sleep time in young adults. characterized by a transition to an EEG with high

amplitude delta EEG waves (1.5 to 3 Hz).

Sleep Architecture

Sleep Architeture

Sleep stages occur in cycles lasting 90-120 min each.

4-5 cycles occur during a typical night of sleep. During the first half of the night, the individual

typically passes from wakefulness briefly into stage 1 sleep and then to stages 2, 3, and 4. Stages 3 and 2 reappear, after which REM sleep is observed for the first time.

During the second half of the night, stage 2 and REM sleep alternate.

Abnormalities of sleep architectureo Narcolepsy REM sleep occurring earlier than 90 to 120 minutes

o Irregular sleep/wake organization, o Withdrawal from certain medications (e.g., tricyclic

antidepressants, MAOI) o Depression.

Sleep disorders will increase the number of sleep stage changes and may completely disrupt the normal cycling of sleep.

REM Latency vs Sleep latency

REM Latency:o The period lasting from the moment of fall asleep

to the first REM period. Last app. 90 min o Depression and narcolepsy are examples of shorten

REM latency Sleep Latency:o The time needed before actually fall asleep .last

app. 15 min o Insomnia is an example of increase sleep latency

Changes with age

Quantity and Quality of sleep change significantly with aging.

Deep or slow wave sleep (stages 3 and 4) declines Light sleep (stage 1) increases. The number of arousals and the amount of

wakefulness also increase in later years.

Multiple sleep latency test

an objective measure of daytime sleepiness used for >15 years the sleepier an individual is, the faster he will fall asleep. The following protocol is typically used:o The patient is given 4-5 opportunities to nap, usually at two

hour intervals during the day. o On each occasion, the individual is asked to lie down on a

bed in a quiet, darkened sleep room and fall asleep as quickly as possible.

o The EEG, eye movements, and muscle tone are measured during the test.

The latency from wakefulness to sleep onset is measured to determine the "sleep latency."

Each session is terminated after 15 minutes of sleep.

The process is repeated during each of the four to five naps, and a mean sleep latency across all the naps is computed.

Minutessleepiness

0-5Severe

5-10Troublesome

10-15Manageable

15-20Excellent

Polysomnogram

Function of Sleep

Function of Sleep

o The Restorative Theory of Sleep, states that some

process during sleep restores tissue and prepares the body for the next day.

o The Adaptive Theory of Sleep proposes that sleep increases survival.

o The Energy Conservation Theory states that a low metabolism for energy conservation is the function of sleep.