Circadian Rhythm: Your Internal 24-Hour Clock
Learn how your circadian rhythm controls sleep-wake cycles, hormone release, and metabolism. Discover how to optimize it for better sleep.
Key Points
- Your circadian rhythm is an internal 24-hour biological clockLight is the primary zeitgeber (time-giver) that resets your clockCircadian misalignment causes insomnia, fatigue, and health issuesConsistent sleep-wake times strengthen circadian rhythmsMorning light exposure is the most powerful circadian reset tool
The Master Clock
Your circadian rhythm is controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus. This master clock regulates when you feel alert vs sleepy, body temperature fluctuations, hormone release (melatonin, cortisol), and metabolism.
How Light Resets Your Clock
Light exposure, especially blue wavelengths, signals to your SCN that it's daytime. Morning light advances your clock (makes you sleepier earlier), while evening light delays it (makes you sleepier later). This is why screen time before bed is problematic—it pushes your internal clock later, creating a mismatch with your desired sleep time.
Practical tip: Get 30+ minutes of bright light (ideally sunlight) within 1 hour of waking. This is more powerful than any supplement.
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