Circadian Health Glossary

CBTmin (Core Body Temperature Minimum)

CBTmin refers to the lowest point of core body temperature during a 24-hour period, typically occurring during the early morning hours. It is a key marker of the body’s circadian rhythm and the transition from the biological night to the day.

Why Is CBTmin Important?

  • Circadian Marker: Indicates the timing of the circadian clock and helps assess sleep-wake cycles

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  • Light Therapy Timing: Light exposure after CBTmin promotes a phase advance, while exposure before CBTmin induces a phase delay.

  • Sleep Regulation: Occurs during the deepest part of sleep and aligns with restorative processes in the body.

When Does CBTmin Occur?

CBTmin typically happens 2 hours before natural wake-up time, though the exact timing varies based on an individual’s chronotype and sleep schedule.

CBTmin is a critical physiological marker for understanding and optimizing circadian health and therapeutic interventions like light therapy.