OBJECTIVE: Adolescents and adults who are evening-types exhibit shorter sleep duration and more sleep problems than individuals with an earlier chronotype. We hypothesized that already at a preschool age, evening-types would exhibit more sleep problems relative to children who are morning or intermediate chronotypes. The aim of this study was to examine the association between chronotype and sleep problems among preschool children.
METHODS: We studied a subset of typically-developing 4.5-year-olds taking part in the Growing Up in Singapore Towards healthy Outcomes birth cohort study (n = 244). The Children's Chronotype Questionnaire (CCTQ) was used to categorize children into morning-, intermediate-, and evening-types. Sleep problems were measured using the Children's Sleep Habits Questionnaire (CSHQ), with higher scores corresponding to greater sleep problems. The relation between chronotype, sleep-wake timing, and nocturnal sleep time was also evaluated in a subsample of 117 children using actigraphy recordings with parent-reported sleep diaries.
RESULTS: After controlling for potential confounders (maternal education, child's sex, birth order, and ethnicity), a significant main effect of chronotype on sleep problems was observed, in which evening-types exhibited greater CSHQ scores compared to morning- and intermediate-types (all p < 0.001). Actigraphy data in the subsample confirmed that evening-types had later bedtimes (p < 0.001) and get-up times (p = 0.02) during weekdays and weekends, but shorter nocturnal sleep time (p = 0.034) only during weekdays, compared to children who had earlier chronotypes.
CONCLUSIONS: In preschool children, sleep problems were greater in evening-types compared to morning- and intermediate-types, suggesting that chronotype could be a contributing factor to sleep disturbances in early childhood.
