Appropriate Lifelong Circadian Rhythms Are Established During Infancy

The biological center of the human circadian rhythm (CR), present in the suprachiasmatic nucleus, plays an important role in controlling life-sustaining functions. The CR supports the daily social activities of modern people; therefore, a regular CR is required to adapt to social life schedules. It is known that the development of the CR begins in the fetal period and is almost completely developed by infancy to early childhood, being deeply related to the balance of mental and physical development in children. The formation of the CR biological clock during the fetal period is influenced by the mother's daily circadian rhythm during pregnancy, while after birth it is influenced by the daily environment of the infant, along with their genetic predisposition. A complete CR affects the maintenance of mental and physical health throughout one's life, while CR disturbances can cause various health problems at all ages; in other words, the formation of an appropriate and stable CR biological clock is extremely important for maintaining mental and physical health throughout one's life. In this study, the elements necessary for the formation of an appropriate CR are discussed.