Circadian Health Glossary

Phase Response Curve (PRC)

A Phase Response Curve (PRC) describes the relationship between a stimulus, such as light exposure, and its effect on shifting the body’s circadian rhythm (phase shift). It illustrates how the timing of the stimulus determines whether it causes a phase delay or phase advance in the circadian cycle.

How Does the PRC Work?

  • Light Exposure Before Minima: Causes a phase delay, making the body’s internal clock run later.

  • Light Exposure After Minima: Leads to a phase advance, shifting the circadian rhythm earlier.

The PRC helps guide the timing of interventions like light therapy to optimize sleep-wake cycles, treat circadian misalignments, and manage disorders like Delayed Sleep Phase Disorder (DSPD) or jet lag.

Why Is the PRC Important?

  • Personalized Light Therapy: Helps determine the best timing for light exposure to achieve desired circadian shifts.

  • Circadian Health Management: Guides treatments for sleep disorders, jet lag, and shift work misalignment.

  • Scientific Research: PRCs are foundational tools for understanding the effects of external stimuli on the biological clock.