Sleep duration trajectories and cognition in early childhood: A systematic review.

Sleep is dynamic in childhood and studies have shown the relationship between sleep and cognition in children. As the human brain is the most plastic during childhood, the study of longitudinal sleep patterns and neurocognition is an important research area. We aimed to systematically review studies that investigated sleep duration trajectories and cognition in typically-developing children. We searched four databases for articles published between 2003 to October 2023. We included observation studies of children with sleep duration trajectories as a predictor and outcomes related to cognition, memory, language, developmental milestones, intelligence or executive function. We excluded studies where children had atypical development or completed the sleep and neurocognitive assessments after six and 12 years of age respectively. Out of 752 articles identified, 511 were screened and 23 full texts were assessed. The selected studies included three single trajectory and four multiple group trajectories studies. We found associations between both types of trajectories and cognitive development. Overall, children with longer sleep trajectories or more mature sleep pattern with rapid decrease in sleep duration, had better performance scores in developmental assessment tools, and intelligence tests. Findings for language and executive functioning were mixed, whereby some studies found associations and others did not.

Beyond Counting Sheep: Exploring the Link between Polycystic Ovary Syndrome and Sleep Health.

Polycystic ovary syndrome (PCOS) is a common hormonal condition with reproductive, metabolic, and psychological sequelae that affects 8 to 13% of reproductive-aged women and 3 to 11% of adolescent girls. Sleep is often compromised in women with PCOS due to increased rates of sleep problems, with the most established problem being obstructive sleep apnea (OSA). OSA is highly prevalent in reproductive-aged adult women with PCOS, but not so in adolescence. The international evidence-based PCOS guideline to improve health outcomes in women with PCOS indicated routine screening to identify and alleviate symptoms of OSA. The guidelines, however, did not weigh other multidimensional constructs of sleep health such as sleep disturbances (e.g., sleep quality and quantity), beyond OSA. This is perhaps due to the lack of research and existing mixed findings in the area of PCOS and sleep health. This narrative review summarizes the current knowledge about OSA and expands further to include the limited knowledge about other sleep problems in PCOS among reproductive-aged women and adolescent girls. We broadly cover the prevalence, risk factors, and mechanisms of sleep problems in PCOS and their relationship with cardiometabolic and psychological health. A brief summary on treatment and intervention strategies for sleep problems in PCOS and future recommendations will be deliberated.

Chronotype and time-of-day effects on spatial working memory in preschool children.

STUDY OBJECTIVES: Spatial working memory (SWM) capacity subserves complex cognitive functions, yet it is unclear whether individual diurnal preferences and time-of-day influence SWM in preschool children. The main and interaction effects of chronotype and time-of-day on SWM and SWM differences in preschoolers with different chronotypes within each time-of-day group will be examined. METHODS: We studied a subset of typically developing 4.5-year-olds taking part in a birth cohort study (n = 359). The Children's Chronotype Questionnaire categorized children into morning-, intermediate-, and evening-types. Using a computerized neuropsychological test (Cambridge Neuropsychological Test Automated Battery), SWM was determined from the total number of between-search errors (ie, between search-total errors) and Strategy scores. Higher between search-total errors or lower Strategy scores indicated worse SWM. Time-of-day was categorized into late morning (10:00 am to 11:59 am), afternoon (12:00 pm to 3:59 pm), and late afternoon (4:00 pm to 6:30 pm). In a subsample (n = 199), caregiver-reported chronotype was validated using actigraphy-measured sleep midpoint. RESULTS: After controlling for ethnicity, no significant main and interaction effects of chronotype and time-of-day on between search-total errors and Strategy scores were seen (all P > .05). However, evening-types outperformed morning-types (ie, lower mean between search-total errors) in the late afternoon (P = .013) but not in the late morning and afternoon (all P > .05). Actigraphy data in the subsample confirmed that evening-types had later sleep midpoints during weekdays and weekends (P < .001). CONCLUSIONS: Since evening-type preschoolers had better SWM in the late afternoon compared to morning-type preschoolers, this gives insights into optimal learning opportunities in early childhood education. CITATION: Abdul Jafar NK, Tham EKH, Eng DZH, et al. Chronotype and time-of-day effects on spatial working memory in preschool children. J Clin Sleep Med. 2023;19(10):1717-1726.

Preconception sleep quality moderates the association between preconception hair cortisol levels and mental health in pregnant women.

BACKGROUND: Poor sleep quality may elevate cortisol levels and affect prenatal mental health through altered HPA axis functioning. This study aims to examine whether subjective sleep quality during preconception moderates the association between preconception hair cortisol levels and mental health from preconception to pregnancy trimesters. METHODS: Women from a prospective cohort study completed the Pittsburgh Sleep Quality Index (PSQI), the Edinburgh Postnatal Depression Scale (EPDS), and the State-Trait Anxiety Inventory (STAI) questionnaires during preconception (T0) and at each pregnancy trimesters (T1, T2, and T3). We analyzed 266 of these women who conceived and had fully completed measures at preconception for hair cortisol, sleep quality and either EPDS or STAI-state. Changes in EPDS and STAI-state scores were derived (i.e., T1-T0, T2-T0, T3-T0). Johnson-Neyman technique identified PSQI scores with significant moderation of cortisol on mental health. RESULTS: After adjusting for potential covariates, there was a significant positive correlation between preconception hair cortisol levels and depressive symptom at the second trimester (rs (144) = 0.22, p = 0.008), but not the first and third trimesters (all ps > 0.05). The positive association between preconception hair cortisol and change in depressive symptoms between third trimester and preconception was significant only among women with poor preconception sleep quality (PSQI ≥ 7). LIMITATIONS: Sleep quality and prenatal mood were derived from self-reported questionnaires, which may be more susceptible to bias. CONCLUSIONS: The positive association between preconception hair cortisol and change in prenatal depressive symptoms is significant among women who reported poor sleep quality during preconception. Improving preconception sleep quality can potentially mitigate the association between preconception hair cortisol and depressive symptoms during pregnancy.

Association between breastfeeding and sleep patterns in infants and preschool children.

BACKGROUND: Although most studies have reported unfavorable short-term effects of breastfeeding on early-childhood sleep-wake behaviors that potentially attenuate over time, findings have remained inconsistent. OBJECTIVES: We assessed associations of breastfeeding with longitudinal day-, night-, and total-sleep trajectories and with sleep-wake behaviors in healthy infants and preschoolers. METHODS: Caregivers of naturally conceived, term, singleton infants (n = 654) completed the Brief Infant Sleep Questionnaire (3, 6, 9, 12, 18, and 24 mo) and/or Children's Sleep Habits Questionnaire (54 mo), and provided information on their infants' breastfeeding status at 3 mo. Trajectory analyses derived 4 day- (n = 243), 3 night- (n = 248), and/or 4 total- (n = 241) sleep trajectories, each differing in length of sleep duration (short/moderate/long) and variability (variable/consistent). Sleep-wake behaviors from 3 to 24 mo (day/night/total-sleep durations and duration/number of night awakenings) were also assessed for associations with breastfeeding. RESULTS: After adjusting for potential covariates, formula-fed infants, relative to fully breastfed (predominant or exclusive) infants, were significantly less likely to exhibit moderate (OR: 0.28; 95% CI: 0.11, 0.70) and long consistent (OR: 0.18; 95% CI: 0.07, 0.50) night-sleep trajectories and less likely to exhibit moderate (OR: 0.21; 95% CI: 0.07, 0.61) and long consistent (OR: 0.12; 95% CI: 0.04, 0.38) and long variable (OR: 0.16; 95% CI: 0.05, 0.56) total-sleep trajectories, instead of short variable night- and total-sleep trajectories. Partially breastfed infants did not differ from fully breastfed infants for both night- and total-sleep trajectories. No significant differences were found between all groups for day-sleep trajectories. Fully breastfed infants had longer night- (6, 9, 12, and 24 mo) and total- (3 and 12 mo) sleep durations than formula-fed infants, albeit a greater number of night awakenings (from 6 to 12 mo). CONCLUSIONS: Despite more night awakenings, fully breastfed infants have overall longer night- and total-sleep durations (sleep trajectories) than formula-fed infants.

Variations in habitual sleep and relational memory in 6-month-olds.

OBJECTIVES: Adequate sleep duration and good sleep quality are considered essential for development, especially during periods of major neurodevelopmental change. Still, relations between parent-reported habitual sleep and emerging cognitive abilities within the first year of life are not well studied. Here, we examined relations between habitual sleep measures and an aspect of cognitive functioning, relational memory, which emerges as early as 6 months of age, as compared to other abilities (ie, recognition memory and attentional orienting), both of which are considered to emerge earlier in development. PARTICIPANTS: Participants were a subset of 267 healthy typically developing 6-month-olds taking part in the Growing Up in Singapore towards Healthy Outcomes cohort study. MEASUREMENTS: Sleep duration, sleep latency, and number and duration of night awakenings were derived from the Brief Infant Sleep Questionnaire (BISQ). Short sleep was defined as <10 hours per day, categorized as "not recommended" based on the National Sleep Foundation recommendations. Associations between sleep variables and infants' performance on 2 relational memory tests (deferred imitation and relational binding) were examined independently using hierarchical (blockwise entry) linear regression. Associations between sleep and recognition memory and attentional orienting were also explored. RESULTS: Habitual short sleepers had poorer relational memory recall in the deferred imitation task compared with 'typical' sleepers (10-18 hours per day). Shorter sleep latency was related to a greater proportion of correct responses for certain aspects of relational binding. There were no associations between sleep and recognition memory or attention. CONCLUSIONS: Our findings suggest that habitual sleep duration and short sleep latency associate with 6-month-olds' relational memory, suggesting a preferential association with memory tasks that are sensitive to development during the second half of the first year.

The association between chronotype and sleep problems in preschool children.

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.