Nearly one third of human life is spent sleeping, which occurs regularly each day in a state of unresponsiveness and calm. Sleep is defined by stages based on EEG, EOG, and EMG patterns, with two main states: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. NREM sleep is further divided into four stages characterized by different brain wave frequencies and muscle movements. REM sleep involves eye movements similar to waking and a lack of muscle movement in the body. Sleep cycles through NREM and REM stages throughout the night, with REM sleep making up 20-25% of total sleep.

1. STAGES OF SLEEP
- Dr. Jeet Nadpara

2. Nearly one third of human life is spent in sleep, an easily reversible
state of relative unresponsiveness and serenity which occurs more
or less regularly and repetitively each day.
States and stages of Sleep
States and stages of human sleep are defined on the basis of
characteristic patterns in the electroencephalogram (EEG),
electro-oculogram (EOG a measure of eye movement activity),
and the surface electromyogram (EMG).

3. The continuous recording of this array of electro-physiologic
parameters to define sleep and wakefulness is termed
polysomnography.
Polysomnographic profiles define two states of sleep:
1. Rapid eye movement (REM) sleep (also known as dreaming,
paradoxical, desynchronized, or ‘D’sleep)and,
2. Non rapid eye movement (NREM)sleep (also known as
orthodox, synchronized or ‘S’ sleep). NREM sleep is in turn
subdivided into four stage.

6. 1. NREM stage 1 is the transition from wakefulness and is characterized
by disappearance of regular alpha pattern and emergence of a low-
amplitude, mixed frequency pattern, pre dominantly in the theta
range (2 to 7 Hz)and slow ‘rolling’ eye movement.
2. NREM stage 2 is defined by the occurrence of K complexes
and sleep spindles superimposed upon a background
activities similar to that of stage 1.

7. K complexes are slow, high amplitude, negative(upward)
discharges followed immediately by a (upward)
discharges followed immediately by a positive downward
reflection.
Sleep spindles are high frequency(12 to 14 hz) discharge
lasting 0.5 to 0.2 seconds with a characteristic waxing and
waning amplitude. Rapid eye movement activity is
absent, and EMG is similar to stage 1.

8. 3. NREM stage 3 is sleep with at least 20 percent but less than 50
percent high amplitude (75V) delta (0.5 to 2 Hz) activity. Sleep
spindles may persist, eye movement activity is absent, and EMG
activity perist at reduced level.
4. In NREM stage 4, the high voltage, slow EEG pattern of stage
3 comprises at least 50 percent of the record.
NREM stage 3 and stage 4 are referred to, collectively,
as a ‘slow wave’, ‘delta’, or deep sleep.

9. REM sleep is characterized by a low amplitude, mixed
frequency EEG similar to that of a NREM stage 1.
Burst of 3 to 5 Hz activity with sharp negative deflection are
often superimposed on this pattern.
The EOG shows burst of REM similar to that seen during
eye opening in wakefulness.
EMG activity is absent, reflecting the complete brainstem-
mediated muscle atonia that is characteristic of that state.

10. Electroencephalogram Electro-oculogram Electromyogram
Wake (eye open) Low amplitude, mixed,
High frequency
Rapid High variable
Wake (eye closed) Low amplitude, alpha (8-
13Hz)
dominates over occipital
region
Absent but slow rolling
eye movements
Reduced
NREM stage 1 Low amplitude, mixed
frequency(alpha absent)
Slow rolling eye
movements
Reduced
NREM stage 2 Low amplitude,
K complexes and sleep
spindles
Absent Reduced
NREM stage 3 Increased amplitude,
Decreased frequency,20
to 30 % delta
Absent Reduced
NREM stage 4 >50% dominated by delta
EEG activity
Absent Reduced
REM Low amplitude, mixed
frequency
Rapid, conjugate Absent

14. Organization of human sleep
• After sleep onset, sleep usually progresses through NREM stage 1 to 4 within 45 to 60 min.
• After the first slow wave sleep episode, the progression of NREM stage reverses.
• The first REM sleep occurs usually not less than 80 min. after sleep begins, although REM
latency shortens with advance age.
• More rapid onset REM sleep in young adult may (particularly if less than 30 min) suggest
pathology such as endogenous depression, narcolepsy, circadian rhythm disorders, or
drug withdrawal.
• NREM and REM alternate through the night with an average cycle of 90 to 110 min.
• As the sleep period lengthens, the proportion of each cycle composed of slow wave
Sleep decreases and that of REM increases.
• Overall, REM sleep is 20 to 25 percent of total sleep, while NREM stage (1to 2) constitute
50 to 60 percent (increasing in elderly subjects).

15. Thank you !