Serum Micronutrient Status, Sleep And Neurobehavioral Function In Early Adolescents: A Cohort Study

Adolescence represents a critical period of neurobehavioral development. Prior research has proposed suboptimal micronutrient and sleep status as individual risk factors for neurobehavioral impairment in adolescents. Additionally, there is a small but growing body of literature that has documented an association between micronutrient status and sleep patterns, suggesting a complex relationship among micronutrients, sleep and neurobehavioral function. It was thus the aim of the present study to provide a systematic review on micronutrients and sleep, empirically examine the associations between micronutrient status and sleep with a focus on early adolescents, and to characterize the contribution of sleep to the relationship between micronutrient status and neurobehavioral function. Study One (Chapter 2) systematically reviewed the existing studies (n=26) on the relationship between micronutrients and sleep across populations, thereby providing the background and generating hypotheses for the empirical sub-studies. Data sets from the China Jintan Child Cohort were used to conduct cross-sectional and longitudinal analyses (n=777) of serum zinc/iron concentrations and adolescent sleep assessed by the Pittsburgh Sleep Quality Index (Chapter 3), as well as a mediation analysis (n=226) of sleep quality between serum iron/zinc and neurobehavioral function in early adolescents aged 11-14 years (Chapter 4). Cross-sectional analyses found significant associations of higher serum zinc concentrations with better global sleep quality, as well as decreased odds of insufficient sleep duration and sleep disturbances in early adolescents. Longitudinal analyses reported a trend towards better sleep efficiency at early adolescence with increasing serum zinc concentrations at preschool age. Serum iron concentrations were significantly associated with concurrent sleep latency but not global sleep quality and other sleep domains in early adolescents. Similarly, the interaction effects between serum iron and zinc on sleep quality did not reach statistical significance. Results of the mediation analyses indicate that early adolescents with low levels of serum iron and zinc were significantly associated with fast but error-prone performance on nonverbal reasoning task. Sleep quality partially mediated the relationship between low serum zinc and non-verbal reasoning but not low iron. Findings from this dissertation study provide preliminary evidence for understanding the multifaceted and interrelated role of micronutrient status, sleep, and neurobehavioral function during early adolescence, which may be useful for developing interventions to optimize sleep-related health in adolescents. Future research is needed to validate and examine the clinical relevance of these findings.