II. Physiology
- Sleep Stages defined by Electroencephalogram changes
III. Epidemiology
- Sleep cycles normalize after 6 months of age
- Average sleep per day
- Infants and children: 16 to 20 hours per day
- Young Adults: 7 to 8 hours per day
- Adults over age 60 years: 6.5 hours per day
IV. Stages: Light Sleep (Non-REM Sleep)
- Stage I of Sleep: Sleep Onset (Drowsy Phase)
- Lowest threshold for arousal
- Time spent in Stage I increases with age
- Accounts for more brief awakenings
- Accounts for fragmented sleep
- Stage II of Sleep: Light Sleep
V. Stages: Deep Sleep or Delta Sleep (Non-REM Sleep)
-
General (Stages 3 and 4)
- Deepest, most refreshing and restorative sleep type
- Diminishes with age
- Highest threshold for arousal
- Associated with diffuse dreams
- Dream about color or emotion
- Associated Conditions
- Night Terrors (Sleep Terrors)
- Sleep Walking
- Confusion on arousal
- Stage III of Sleep
- Stage IV of Sleep
VI. Stages: Rapid Eye Movement Sleep (REM Sleep)
- Timing
- REM occurs cyclically every 90 minutes of sleep
- Infants spend 50% of sleep time in REM Sleep
- Adults spend 20% of sleep time in REM Sleep
- Dream Characteristics
- Most recallable dreams during this stage
- Bizarre and detailed dreams during this stage
- Signs
- Suppressed voluntary motor activity ("paralyzed")
- Rapid eye movements
- Associated Sleep Conditions
- Nightmares and Frightening Dreams
- Sleep-related painful Erections
- Provocation of Medical Symptoms