Circadian Biology
TL;DR
Circadian biology is the 24-hour timing architecture that coordinates sleep-wake behavior, hormone timing, metabolism, temperature, immune signaling, and cellular repair. The master clock is centered in the suprachiasmatic nucleus (SCN), but most tissues also run peripheral clocks that need to stay phase-aligned with light, food timing, and activity.
Why it matters for Vitals
- Sleep timing is not just a comfort variable; it is a systems-timing variable.
- Circadian disruption can distort HRV, resting heart rate, glucose handling, sleep architecture, and subjective readiness.
- The Vitals product should treat circadian state as a context layer for interpreting recovery, metabolic, and coaching signals.
Core system
- SCN master clock: synchronizes to light, especially morning light.
- Peripheral clocks: liver, muscle, adipose, gut, immune cells.
- Key clock genes: CLOCK, BMAL1, PER, CRY, REV-ERB, ROR.
- Primary zeitgebers: light, meal timing, exercise timing, sleep timing, social timing.
High-value implications
- Stable wake time generally matters more than perfect bedtime.
- Morning light strengthens circadian amplitude.
- Late bright light, late meals, and erratic sleep timing weaken internal alignment.
- Circadian alignment affects both metabolic flexibility and the scheduling of repair pathways.