Elsevier

Sleep Medicine

Volume 30, February 2017, Pages 240-244
Sleep Medicine

Brief Communication
The association between chronotype and sleep problems in preschool children

https://doi.org/10.1016/j.sleep.2016.11.015Get rights and content

Highlights

  • Chronotype is linked with reported sleep problems among preschoolers.

  • Preschoolers with evening chronotype exhibit greater reported sleep problems.

  • Actigraphy associated chronotype with reported sleep problems on weekdays.

  • Cultural-related lifestyle and parental practices may contribute to sleep problems.

Abstract

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.

Introduction

Sleep problems that start in early childhood often persist across development [1], [2], [3], and have been associated with negative behavioral, cognitive, and emotional health consequences [2], [4]. It is known that sleep problems are often caused by irregular sleep habits [5], [6], [7] and poorly enforced bedtime routines [5], [6] such as irregular sleep–wake schedules. In adolescents and adults, chronotype is thought to be a stable trait that contributes to individual differences in sleep–wake timing [8], [9]. A person's chronotype reflects his or her preferred timing of sleep and waking activities [7], which is linked to psychosocial behavior and specific properties of the circadian clock [8], [9], [10].

In children, chronotype is often divided into three different categories: “morning,” “intermediate,” and “evening” chronotypes. Evening-types exhibit later habitual bedtimes and sleep onset times independent of environmental factors (such as parenting), in comparison to morning-types, as evidenced by actigraphy [7], [11]. However, little is known about whether individual differences in chronotype contribute to sleep problems in preschool children who have yet to be exposed to the formal education system and fixed school start times. In the present study, we therefore aimed to assess whether typically developing Singaporean preschoolers who are evening-types exhibit greater sleep problems than those who are morning- or intermediate-types.

Section snippets

Study design and sample

The present study was carried out as part of the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort study, which recruited 1247 pregnant women aged ≥18 years during the first trimester of pregnancy. Socio-demographic information was collected upon enrollment. Women were recruited from two major public hospitals in Singapore: KK Women's and Children's Hospital, and the National University Hospital. All births occurred between 30 November 2009 and 1 May 2011. Further details

Sleep–wake timing

The actigraphy-estimated average (standard deviation [SD] in hours) bedtime and get-up time based on mother-reported child sleep diaries were respectively 23:01 (0:59) and 08:02 (01:00). Average bedtimes for morning-, intermediate-, and evening-types during weekdays were respectively 21:55 (01:00), 22:44 (0:48), 23:02 (0:58), and during weekends were respectively 22:21 (01:23), 23:12 (01:03), and 23:34 (01:15). Average wake for morning-, intermediate-, and evening-types during weekdays were

Discussion

We found that Singaporean preschoolers who were evening-types had greater parent-reported sleep problems in comparison to morning- and intermediate-types. Additionally, in a subsample, sleep diaries and actigraphy were used to confirm that children who were categorized as evening chronotypes on the CCTQ indeed had later bedtimes and get-up times during weekdays and weekends, and shorter nocturnal sleep time during weekdays compared to morning- and intermediate-types. Our results are consistent

Acknowledgments

We thank the GUSTO study group and all of the participants in this study. We also thank Mr. Desmond Neo for his assistance in coding of the actigraphy data and questionnaires. This research was supported by the Singapore National Research Foundation (NMRC/TCR/004-NUS/ 2008; NMRC/TCR/012-NUHS/2014) under its Translational and Clinical Research (TCR) Flagship Programme and administered by the Singapore Ministry of Health's National Medical Research Council (NMRC), Singapore-NMRC/TCR/004-NUS/2008;

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