Sleep Stages
Wakefulness
- W - Wakefulness
- Characterized by alpha waves (posterior dominant, 8 - 12 Hz frequency, observable on eyelid closure).
Non-REM Sleep
- N1 - Stage 1 - 5%
- Low-amplitude mixed-frequency (LAMF). For instance, theta activity. Vertex waves can be observed.
- N2 - Stage 2 - 50%
- N3 - Stage 3 - 20%
- Slow wave activity (delta frequency) greater than 20% of the 30 second page.
REM Sleep
- R - REM - 25%
- Rapid eye movements and saw-toothed waves.
- Occurs ~ every 90 minutes; 4 times per night; length of REM extends with every epoch of REM during the night and the time between REM epochs reduces during the course of the night. Less REM earlier in the night/More REM later in the sleep phase.
Effects of items on Sleep Stages
Age
- INCREASE in overall sleep latency (time to falling asleep) and REM latency (time to first REM cycle).
- DECREASE in REM sleep.
- INCREASE in sleep fragmentation.
Depression
- INCREASE in REM sleep (and also a reduction in REM latency).
- ALTERATION in the distribution of N3 sleep throughout the night.
- INCREASE in insomnia (especially difficulties with maintenance of sleep); less common is hypersomnia.
Antidepressants (broad generalization)
- DECREASE REM sleep (and increase REM latency)
- As one important exception, buproprion does NOT significantly affect sleep (it does NOT impact REM sleep).
- INCREASE N3 sleep.
- Sedating agents (tricyclic antidepressants) INCREASE sleep continuity.
- Non-sedating agents (eg, serotonin-norepinephrine reuptake inhibitors) can DECREASE sleep continuity.
Alcohol Abuse
- DECREASE in sleep continuity.
- DECREASE in N3.
- INCREASE in REM.