Normal Sleeping JameelAdnan, MD. Community & Primary Health CareKAAU-RABEG BRANCH
Round Map • Introduction • Sleep Stages • Sleep Architecture • REM Latency vs Sleep latency • Changes with age • Function 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 • Two general states: • Rapid Eye Movement sleep (REM) • Non-Rapid Eye Movement sleep (NREM). • NREM sleep is further subdivided into four NREM stages.
1. REM Sleep • The brain is active, and the body is inactive. • three main features: • A low voltage, fast frequency EEG pattern • The presence of rapid eye movements • An atonicelectromyogram (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) • Consistent with inactivity of all voluntary muscles except the extraocular muscles • The individual is paralyzed during REM sleep. • 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 • Phasic REM sleep. • Tonic REM sleep.
1. REM Sleep • 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. • 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 • 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: • 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. • 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 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 architecture • Narcolepsy REM sleep occurring earlier than 90 to 120 minutes • Irregular sleep/wake organization, • Withdrawal from certain medications (e.g., tricyclic antidepressants, MAOI) • 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: • The period lasting from the moment of fall asleep to the first REM period. Last app. 90 min • Depression and narcolepsy are examples of shorten REM latency • Sleep Latency: • The time needed before actually fall asleep .last app. 15 min • 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: • The patient is given 4-5 opportunities to nap, usually at two hour intervals during the day. • 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. • 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.
Function of Sleep • The Restorative Theory of Sleep, states that some process during sleep restores tissue and prepares the body for the next day. • The Adaptive Theory of Sleep proposes that sleep increases survival. • The Energy Conservation Theory states that a low metabolism for energy conservation is the function of sleep.