The approximately 24-hour internal biological clock that regulates sleep-wake cycles, hormone release, body temperature, and other physiological processes. Circadian rhythms are primarily synchronized by light exposure and are governed by the suprachiasmatic nucleus (SCN) in the hypothalamus.
Circadian rhythms are approximately 24-hour cycles in biological processes that regulate sleep and wakefulness, hormone secretion, body temperature, metabolism, and many other physiological functions. The word 'circadian' comes from the Latin 'circa diem,' meaning 'about a day.' These rhythms are endogenous (internally generated) but are synchronized to the external environment primarily through light exposure.
The master circadian clock resides in the suprachiasmatic nucleus (SCN), a small region in the hypothalamus that receives direct light input from specialized photoreceptive cells in the retina. The SCN coordinates peripheral clocks throughout the body, ensuring that physiological processes are appropriately timed. Key circadian-regulated processes include melatonin secretion (promoting sleep onset), cortisol release (promoting wakefulness), body temperature fluctuations, and cognitive performance cycles.
Disruption of circadian rhythms — through shift work, jet lag, irregular sleep schedules, or excessive artificial light at night — is associated with sleep disorders, mood disturbances, impaired cognitive function, metabolic dysfunction, and increased health risks. Supporting healthy circadian rhythms through consistent sleep-wake schedules, morning light exposure, limiting evening blue light, and aligning meals with daytime hours is a foundational wellness practice with far-reaching effects on physical and mental health.
A circadian rhythm is the approximately 24-hour internal biological clock that regulates sleep-wake cycles, hormone release, body temperature, and other physiological processes. It is governed by the suprachiasmatic nucleus in the hypothalamus and primarily synchronized by light exposure.
Support circadian health through consistent sleep-wake schedules, morning bright light exposure, limiting blue light in the evening, eating meals during daytime hours, and maintaining a cool, dark sleeping environment. Regularity and light timing are the most important factors.
Circadian disruption from shift work, jet lag, or irregular schedules is associated with sleep disorders, mood disturbances, impaired cognition, metabolic dysfunction, and increased health risks. The body's internal processes become misaligned with the external environment.
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