周歲前睡眠節律變化與兩歲語言 成長速度之關連性

Purpose This study investigated whether infants’ circadian rhythm before 1 year of age would predict their language development between 12 and 24 months of age. Specifically, this study addressed three topics: circadian rhythm development in early infancy, whether the development of the circadian rhythm before 1 year of age would benefit language development at 2 years of age, and whether the language development of newborns with a developed circadian rhythm by 3 months of age would be faster during the second year of life than would that of other newborns. Design/methodology/approach This study used five-wave data from the Kids in Taiwan: National Longitudinal Study of Child Development and Care Project. Sleep and language data were collected from infants aged 3, 6, 12, 18, and 24 months. A total of 3,563 participants were included in the final analysis. Multilevel linear models were used to explore the association between the development of the circadian rhythm before 1 year of age and language development at 2 years of age, with demographic factors and language learning environment controlled for. In these models, circadian rhythm development at 3, 6, and 12 months of age was classified as four categories, “development before 3 months of age”, “development at 3–6 months of age”, “development at 6–12 months of age”, and “change at 1 year of age” to serve as the independent variables. The slope of language development at 12, 18, and 24 months of age was the dependent variable. Findings/results Approximately 60% of the participants developed a circadian rhythm by 3 months of age; however, 8% exhibited irregular rhythms at 12 months of age. Those who developed a circadian rhythm by 3 months of age exhibited stronger language skills and faster language development from 12 to 24 months of age than did those who either exhibited an irregular circadian rhythm between 3 and 12 months of age or developed a circadian rhythm at 6 months of age. Originality/value This cohort study is one of few to explore the longitudinal associations between the development of the circadian rhythm at 3–12 months of age and language skills at 12–24 months of age, when infants begin to rapidly learn their native language. We discovered that the development of the circadian rhythm before 1 year of age was associated with language development at 2 years of age. The findings indicate a cross-domain developmental cascade between sleep and language during the first 2 years of life. Suggestions/implications The circadian rhythm is stable before infants’ first birthdays, and individual variation in circadian rhythm development occurs during the first year. The development of the circadian rhythm could be considered a risk factor in assessments of early language development.