Slow-wave sleep

Slow-wave sleep (SWS), often referred to as deep sleep, is the third stage of non-rapid eye movement sleep (NREM), where electroencephalography activity is characterised by slow delta waves.

Slow-wave sleep usually lasts between 70 and 90 minutes, taking place during the first hours of the night. Slow-wave sleep is characterised by moderate muscle tone, slow or absent eye movement, and lack of genital activity. Slow-wave sleep is considered important for memory consolidation, declarative memory, and the recovery of the brain from daily activities.

Before 2007, the term slow-wave sleep referred to the third and fourth stages of NREM. Current terminology combined these into a single stage three.:291