Back to top

circadian rhythm

An innate daily fluctuation of physiologic or behavioral functions, including sleep-wake states generally tied to the 24-hour daily dark-light cycle. It sometimes occurs at a measurably different periodicity (e.g., 23 or 25 hours) when light and dark and other time cues are removed.


Definition reprinted with permission from Culebras, Antonio, Clinical Handbook of Sleep Disorders, Butterworth-Heinemann


Books, etc.