slowwavesömnen

Slowwavesömnen, or slow-wave sleep, is the deepest phase of normal sleep and a major component of non-rapid eye movement sleep (NREM). It is characterized by high-amplitude, low-frequency brain activity, with delta waves in the 0.5–4 Hz range dominating the electroencephalogram. During slowwavesömnen, consciousness is markedly reduced and awakening is more difficult than in lighter sleep stages; heart rate, blood pressure, and respiration slow, and muscle tone remains lower than in wakefulness but higher than in REM sleep.

The distribution of slowwavesömnen varies across the night, being most prominent in the first half of sleep and diminishing in the later cycles. Its amount is also influenced by age and prior wakefulness. Sleep deprivation increases slow-wave activity as part of a homeostatic rebound, reflecting the brain’s response to extended wakefulness.

Functions associated with slowwavesömnen include memory consolidation, particularly for declarative information, and synaptic downscaling which may help optimize learning capacity. The glymphatic system, more active during slow-wave sleep, facilitates the clearance of metabolic waste from the brain. Growth hormone secretion and thermoregulation are also linked to this sleep stage, supporting development and restoration.

Clinical relevance varies with age and health status. Reductions or fragmentation of slowwavesömnen are observed in aging, obstructive sleep apnea, depression, and various neurodegenerative conditions, and such changes can correlate with cognitive or daytime functioning. Treatments that improve sleep continuity can help preserve slow-wave sleep and its associated restorative processes.