Sleep quantity and quality have been verified to influence cognitive function in adult and children, while little is known about such relation among young children. This study aims to explore the concurrent association between sleep and neuropsychological development in infants and toddlers. 1102 children aged 2-30 months old from 16 hospitals in 8 provinces of China were involved in the survey. Main caregivers were asked to fill out the Brief Infant Sleep Questionnaire (BISQ) and the Bayley Scales of Infant Development I (BSID-I) was conducted to evaluate children's neuropsychological development. Results showed that in average infants slept 12.40 (12.30-12.51) hours over 24 hours, woke up 1.77 (1.69-1.84) times per night and woke 0.50 (0.45-0.54) hour through the night. Prolonged night waking duration was negatively associated with the Mental Development Index (MDI) only among toddlers aged 1-2.5 years old (β=-0.10, p=0.045). No association between sleep and psychomotor development was found. This study underscores the high prevalent fragmental sleep in Chinese infants and toddlers that indicates for concurrent slow cognitive development.
night
waking;
cognition
The important role of sleep on cognitive function has been
widely acknowledged in elderly population and healthy
adults
Comparing with preschoolers and adults, infants and
toddlers spend much more time on sleep when their brains
develop rapidly during the first few years
In addition, early well-being is critical for later global
health. For instant, a longitudinal study shows that cognitive
abilities such as attention, processing speed and memory
during infancy and toddlerhood, are predictive for children’s
executive functions including working memory, inhibition
and shifting at 11 years old
Despite of the abundant evidences in children, only
sporadic studies have explored the role of sleep in infants’
cognitive development with most of them coming from
laboratory settings with small sample sizes and narrow age
ranges
From October 2012 to March 2013 in collaboration with one downtown hospital and one suburban hospital in each of the eight provinces in mainland China (i.e., Inner Mongolia, Hunan, Hebei, Guangxi, Yunnan, Shandong, Zhejiang and Jiangsu), we recruited children who came in the clinic for regular health examination. Shanghai Children’s Medical Centre Human Ethics Committee granted ethical approval for this study (SCMCIRB-2012047), and written informed consent was obtained from caregiver of each participant.
In all, 1102 children within the age range of 2-30 month-old born over 37 weeks of gestational age were enrolled. Children were excluded if they were twins or triplets, had any congenital diseases or adverse birth outcomes.
Sleep assessment Parents or primary caregivers completed
the Chinese version of Brief Infant Sleep Questionnaire
(BISQ)
Cognition assessment General cognitive functioning was assessed with the Bayley Scales of Infant Development (BSID-I), the standardized diagnostic test of cognitive development delay for children aged 2-30 months in mainland China. Based on the test scoring, Mental Development Index (MDI) and Psychomotor Development Index (PDI) were derived. All assessments were conducted by well-trained pediatricians.
An initial examination of the data was performed to test for normality and outliers. If normality was not fulfilled then the data was transformed accordingly, e.g., night waking duration was analyzed by log10 (raw data +1) transformation.
The MDI and PDI across gender, parental education level and area were compared by ANOVA. The associations between sleep parameters and Bayley scores were tested by partial correlation adjusted for children’s age. Linear regression analysis was applied to test the predictive effect of sleep parameter on Bayley scores. Children’s age, gender, maternal education level and recruited province were entered as control confounders in each model. The statistical significance level was set at 0.05.
The mean age of the 1102 children was 371.95 (375.24386.56) days, 53.8% (593/1102) of the sample were boys. Boys and girls were of similar age (t(1100)=-1.16, p=0.246).
On average, infants slept 12.40 (12.30-12.51) hrs every day. No differences of total sleep were found between girls and boys (t(1089)=0.88, p=0.378).
Figure 1 showed infants’ night waking frequency and duration across age groups. In general, infant woke up 1.77 (1.69-1.84) times per night and woke 0.50 (0.45 - 0.54) hr through the night. Overall, boys woke up more frequently than girls (t(1097)=2.22, p=0.027). No differences of total night waking duration were found between girls and boys (t(1082)=1.56, p=0.145).
Night waking duration
Night waking frequency 3.0 2- 3- 4- 5- 6- 9- 12- 15- 18- 21- 24-30
Age (months)
The mean MDI and PDI score was 103.13 (102.12-104.14) and 101.97 (101.03-102.91). There was no gender difference regarding to MDI and PDI scores (p>0.05). Parental education levels were highly correlated (r=0.73, p<0.001) and both were significantly associated with MDI and PDI (p<0.001).
Partial correlation, controlled for age, showed that infant night waking frequency and total night waking duration were negatively associated with MDI (r=-0.06, p=0.040; r=0.08, p=0.014), but not associated with PDI (r=-0.01, p=0.740; r=-0.04, p=0.229). Infant total sleep duration was correlated with neither the MDI nor the PDI (r=-0.03, p=0.342; r<0.01, p=0.885).
Linear regressions indicated that prolonged night
waking duration had an adverse impact on MDI only among
toddlers aged 1-2.5 years old (β=-0.10, p=0.045). Neither
total sleep duration or night waking frequency predicted for
MDI in the model (Table 1).
This study underscores the high prevalent and long lasting
night waking problem among Chinese infants and toddlers
with equivalent total sleep duration comparing with
previous meta-analysis
The current results showed that night waking duration
negatively predicted for cognitive development only among
toddlers beyond one year old and highlighted the
impairments of sleep fragmentation. Previous study
involving 1385 Chinese Kindergarten children aged 5.7
years old also showed that children with parental reported
difficulties in maintaining sleep scored peculiarly lower in
verbal IQ (tested by Wechsler Preschool and Primary Scale
of Intelligence-Revised)
More and more studies reveal the importance of infant
sleep quality, rather than sleep duration, which associates
with infants’ cognitive functions. On one hand, frequent and
persistent night waking definitely disturbed sleep continuity,
and the consequent increasing of stress level could impair
infants’ mental performance
The positive effect of sleep on motor development in
children was not supported in the current study. A previous
study using procedural tasks (e.g., the serial reaction time
task, the finger sequence tapping task and the mirror tracing
task) confirmed the absence of sleep-dependent gain in
motor skills in children
There are two major limitations of this study. Firstly, this
study was based on parental report. Future studies
evaluating sleep by both objective and subjective methods
may wish to confirm the results. Secondly, the current study
was designed as a cross-sectional survey, so that only
concurrent associations between sleep and cognition were
derived. Nevertheless, under the context of development,
the correlations and predictive directions between sleep and
cognitive function are not always uniform
Parent-reported night waking problem in Chinese infants
and young toddlers was more prevalent than that in other
countries and sustained during the first few years. Our
findings underline the negative prediction of the sustained
long night waking on young children’s cognitive
development. Thus, apart from the increasing awareness
involved in infant sleep duration, pediatricians and other
professionals should pay more attention to the fragmental
sleep. The current study provides both scientific and clinical
values as our results could be referenced for future
parentaleducated sleep intervention programs to effectively improve
sleep in young children
We’d like to acknowledge the children and their families for
their participation. We thanked the 16 hospital in 8
provinces for their corporations. The study was supported
by Chinese National Natural Science Foundation
(81172685); the Ministry of Science and Technology of
China (2010CB535000); Ministry of Health (201002006);
Shanghai Science and Technology Commission
(12411950405，13QH1401800); Shanghai Key Discipline
of Public Health ;Shanghai Municipal Committee of
Education