Circadian Rhythm
Also known as: Body Clock, Internal Clock, Sleep-Wake Cycle
The roughly 24-hour internal biological clock that regulates sleep-wake cycles, hormone release, and other physiological processes.
FULL EXPLANATION
Circadian rhythm is your body's internal clock that operates on a roughly 24-hour cycle, regulating when you feel sleepy or alert, along with hormone release, body temperature, and metabolism.
The master clock is located in the suprachiasmatic nucleus (SCN) in the brain and is primarily synchronized by light exposure. When circadian rhythm is disrupted (jet lag, shift work, irregular schedules), it affects sleep quality, metabolism, mood, and overall health.
WHY IT MATTERS
Circadian disruption is linked to metabolic disorders, cardiovascular disease, mental health issues, and increased cancer risk. Maintaining strong circadian rhythms is fundamental to health.
HOW TO IMPROVE
Strengthen circadian rhythm through morning sunlight exposure, consistent wake times, limiting evening blue light, eating meals at regular times, and avoiding late-night exercise.
NORMAL RANGES
Natural circadian periods vary slightly from 24 hours. Chronotype (natural sleep-wake preference) varies from early birds to night owls, with most people falling in between.
RELATED TERMS
REM Sleep
A sleep stage characterized by rapid eye movements, vivid dreaming, and muscle paralysis, critical for memory consolidation and emotional processing.
Deep Sleep
The most restorative sleep stage characterized by slow brain waves, essential for physical recovery, immune function, and growth hormone release.
Cortisol
The primary stress hormone that regulates metabolism, immune response, and the body's fight-or-flight response.
Sleep Quality
A measure of how well sleep restores and recovers the body, beyond simple sleep duration.
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Well-EstablishedA sleep stage characterized by rapid eye movements, vivid dreaming, and muscle paralysis, critical for memory consolidation and emotional processing.
Sleep Latency
Well-EstablishedThe time it takes to transition from full wakefulness to sleep after getting into bed with the intention to sleep.
Sleep Efficiency
Well-EstablishedThe percentage of time spent actually sleeping versus total time in bed, a key indicator of sleep quality.