Sömnstadium

Sömnstadium is the Swedish term for sleep stage, referring to the distinct phases of human sleep identified in sleep research. In modern practice, sleep is divided into non-REM (NREM) sleep and rapid eye movement (REM) sleep. NREM comprises three stages: N1 (light sleep), N2 (intermediate sleep with sleep spindles and K-complexes), and N3 (slow-wave sleep, deep sleep). REM sleep features desynchronized brain activity, rapid eye movements, and reduced muscle tone, and is often associated with dreaming. These stages are typically measured with polysomnography, which records EEG, eye movements and muscle tone.

During a night's sleep, cycles of NREM and REM repeat roughly every 90 to 110 minutes, with REM periods lengthening toward morning. The amount and distribution of each stage vary with age, circadian timing, and health. Deep NREM sleep (N3) is linked to physical restoration and growth-related processes, while REM sleep is linked to emotional regulation and memory consolidation.

Disorders and disruptions can alter sömnstadium architecture: insomnia may reduce total sleep and the proportion of restorative stages; sleep apnea can fragment NREM and REM; narcolepsy often affects REM onset. Because of its centrality to sleep medicine, the concept of sömnstadium is widely used in Swedish clinical literature alongside the international NREM/REM framework.