Analysis of factors associated with development of sleep-wake rhythm in early infancy indicated by melatonin secretion

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The Objective of this study was to understand the relationships among sleep developments, crying episodes and salivary melatonin during early infancy more accurately by longitudinal and objective sleep evaluations. Study design was a prospective longitudinal study of infants in the first 4 months of postnatal life. The study included 31 healthy term infants. At approximately 4-6 week intervals, when the infants were age 4-6 weeks, 8-10 weeks, and 14-16 weeks, their mothers were asked to record the crying/fussy behavior of her infant in a timetable and to attach an actigraph to their infant for 3 days. At 14-16weeks, measurements of daily salivary melatonin (4 times per day) were additionally performed. The relationship between the actinographic sleep parameters and duration of crying/fussy behavior per 24 hours was examined from both cross-sectional (age group) and longitudinal (individual) perspectives. The relationship between salivary melatonin concentrations and the actinographic s … More leep parameters or duration of crying/fussy were also evaluated at 14-16 weeks. When the relationships were examined from a cross-sectional perspective, a weak but significant correlation was found in only one sleep parameter, percent of active sleep per total sleep, at only one measuring point, at 14-16 weeks of age (r=0.44, p=0.02). However, when the data were examined from a longitudinal perspective, there were significant relationships between the duration of crying/fussy behavior and percent of active sleep per total sleep (r=0.36, p=0.006), episodes of sleep per 24 hr (r=0.36, p=0.007), and percent of sleep during night (p=0.02, r=-0.31). These results suggested that subsiding of early crying and sleep development reflected by these sleep parameters in infants are parallel phenomenon. Furthermore, the results suggested that an increased percentage of active sleep may be characteristic among infants who still cry frequently at the age of 3 months. Daily salivary melatonin concentrations of infants at 14-16 weeks were not associated with actinographic sleep parameters or duration of crying/fussy. Less