Sömndrivkraft

Sömndrivkraft, a Swedish term roughly translating to 'sleep-driving force', describes the integrated drive to sleep generated by the body's sleep regulation system. In sleep science, it is closely aligned with the concept of sleep propensity or sleep pressure, primarily governed by the interaction of two processes: the homeostatic sleep drive (Process S) that increases with time awake, and the circadian process (Process C) that modulates the timing of sleep according to the 24-hour cycle.

Biological basis includes adenosine accumulation during wakefulness contributing to increasing sleep pressure; the ventrolateral preoptic nucleus promotes sleep onset, while wake-promoting networks in the hypothalamus and brainstem suppress sleep. Sömndrivkraft is reinforced by sleep debt and attenuated by factors such as regular sleep, caffeine, and light exposure.

Measurement and variation: It is not a single measurable quantity but is inferred from subjective sleepiness ratings and objective markers such as latency to sleep in tests like the multiple sleep latency test (MSLT) and actigraphy patterns. It varies across individuals and contexts, and is highest when wakefulness persists and circadian rhythms favor nocturnal sleep.

Influence and disorders: Chronic sleep deprivation amplifies sömndrivkraft; circadian misalignment can shift or weaken sleep propensity, contributing to insomnia, hypersomnia, or irregular sleep-wake patterns. Understanding sömndrivkraft helps explain why people feel sleepy at certain times and how sleep disorders develop.

Management: Good sleep hygiene, timed light exposure, regular schedules, and, when needed, medical interventions targeting sleep pressure or circadian timing may adjust sömndrivkraft.

See also: two-process model of sleep, adenosine, sleep regulation.