Glossary of Sleep-related terms

Stage 2 (NREM Stage 2)

Stage of NREM sleep characterized by the advent of sleep spindles and K complexes against a low-voltage, mixed frequency EEG background similar to stage 1. Stage 2 sleep is usually free of slow rolling eye movements. A more intense stimulus is required to wake someone from stage 2 than from stage 1. In adults, stage 2 typically accounts for 45-55% of total sleep time.1