Sømmen

Sömnen, the Swedish term for sleep, denotes a natural, reversible state of reduced consciousness and responsiveness that occurs in humans and many other animals. During sömnen, movement and sensory input are diminished, while brain activity follows characteristic patterns that differ from wakefulness. The state is essential for various physiological and cognitive functions.

In humans, sömnen unfolds in repeated cycles of about 90 minutes, alternating between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM includes stages N1 to N3, with N3 often referred to as deep sleep and associated with slow brain waves and bodily restoration. REM sleep features active brain activity, dream-rich experiences, and temporary muscle atonia. The balance and progression through these stages support memory consolidation, learning, and emotional regulation.

Regulation of sömnen is guided by the circadian system, primarily controlled by the brain’s suprachiasmatic nucleus, which aligns sleep-wake patterns with light-dark cycles. Light exposure promotes wakefulness; reduced light in the evening facilitates sleep. Melatonin, secreted by the pineal gland, helps signal sleep onset. Environmental and behavioral factors, including caffeine, stress, and shift work, can influence sömnen.

Adequate sömnen is linked to metabolic, cardiovascular, and immune health, as well as cognitive performance. Chronic sleep deprivation or disorders such as insomnia, sleep apnea, hypersomnia, and narcolepsy can have adverse consequences. Sleep needs vary by age and individual factors, but most adults aim for several consecutive hours of restorative sømnen per night.