INDIVIDUAL VARIATIONS IN ORCADIAN RHYTHM FUNCTIONS(<Special Issue>the Scientific Insight into Population)

Abstract

Many physiological and behavioral functions in humans show a near 24-hour (circadian) rhythm in accordance with the rotation of the earth. It is known that there are inter- and intra-individual differences among circadian functions in humans. Chronotype, age and sex are primary factors that mediate the phenotype of individual circadian functions; however, several environmental factors such as the external light-dark cycle also modulate the individual circadian phenotype. Measuring circadian functions should thus provide useful information to establish physiologically optimal conditions in everyday life, but possible confounding factors should be carefully considered.