Table 1.
Physiological features of sleep in older adults.
| Wakefulness | NREM Sleep (75–85% TST) | REM Sleep (15–25% TST) |
|||
|---|---|---|---|---|---|
| N1 (5–10%) | N2 (45–55%) | N3 (15–20%) | |||
| Brain activity (EEG) | High (predominant beta rhythm) | Slowing down (rhythmic alpha and theta waves) | Mostly slow (sleep spindles and K complex) | Slow (high-voltage delta waves) | High (desynchronized, low-voltage, mixed-frequency waves and sawtooth waves); dreaming |
| Eye movements (EOG) | Voluntary gaze movements | Slow eye rolling | Rare | Rare | Rapid eye movement |
| Muscle activity (EMG) | High muscle activity | Moderate - low | Low -moderate | Low | Muscle atonia, except for short episodes of phasic muscle activation and limb twitches |
| Autonomic activity | Variable according to environmental changes | Reduced | Reduced | Reduced | Increased |
EEG: electroencephalography; EMG: electromyography; EOG: electrooculography; N1: stage 1; N2: stage 2; N3: stage 3; TST: total sleep time.