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Colic, sleep inertia, melatonin and circannual rhythms
Insights
Infant colic, characterized by crying, may stem from a developmental delay in regulating sleep-wake cycles due to the absence of a melatonin rhythm. This circannual photoperiodic process concludes around three months postpartum, aligning with colic
Area of Science:
- Pediatric sleep science
- Chronobiology
- Infant development
Background:
- Colic is common in infants during the first three months, marked by daily crying episodes.
- The cause of colic is unknown, but theories suggest sleep inertia or state dissociation due to immature circadian rhythms.
- Melatonin, a hormone regulating sleep-wake cycles, is influenced by light and develops postnatally.
Purpose of the Study:
- To investigate the hypothesis that infant colic is related to the development of the melatonin diurnal rhythm.
- To explore the role of photoperiodic cues and circannual development in infant crying.
- To examine the correlation between colic incidence and geographic latitude.
Main Methods:
- Review of existing hypotheses regarding colic and infant circadian rhythms.
- Analysis of the proposed melatonin timing mechanism and its prenatal and postnatal development.
- Presentation of data correlating colic incidence with increasing latitude.
Main Results:
- The incidence of infant colic increases with increasing latitude.
- This finding supports the hypothesis that colic is linked to the final stages of a circannual photoperiodic development process.
- Infants may struggle to reconcile internal circadian rhythms with external photoperiods during the first three months.
Conclusions:
- Infant colic during the first three months may represent the concluding phase of a circannual photoperiodic development.
- The developing melatonin rhythm and its interaction with environmental light cues are critical factors.
- Further research into the role of photoperiodicity in infant sleep regulation is warranted.
Abstract:
Colic is periodic behavior occurring at the end of the day during the first 3 months of life characterized by crying. It is hypothesized that the crying at the end of the day is due to sleep inertia or a state dissociation during which the infant is simultaneously partially awake and partially asleep because of the absence of a melatonin diurnal rhythm. The melatonin timing mechanisms, which codes for day length, is initiated prenatally by the maternal pineal gland, and after 3 months postnatally, the melatonin nocturnal secretion rhythm is maintained by the infant's pineal gland. To record the seasonal variation in day length away from the equator, 12 months are required to complete the melatonin chemical calendar. This circannual process is only 9 months completed at the time of birth, and 3 additional months are needed during which the infant may have difficulty reconciling cues for the timing of evening sleep due to discrepancies between the expected photoperiod derived from the prenatal maternal pineal melatonin circadian rhythm and the postnatally experienced photoperiod. Data is presented showing that the incidence of colic increases with increasing latitude in support of the hypothesis that infant crying at the end of the day during the first 3 months represents the last quarter of a circannual photoperiodic development process.