The Joint Association Of Sleep And Physical Activity On Cognitive Abilities In Preschool Children

Accumulating evidence indicates that adequate sleep and appropriate physical activity(PA)is a necessary condition during the growth for children and adolescents,which has beneficial effects on body growth,immunity functioning,and emotional and cognitive functioning.As the current substantial pressure on children,parents,and schools to maximize academic performance and with the popularization and application of electronics,sleep problems and lack of physical activity frequently occur in childhood,and are considered as global public health issues.Preschool age is the key period of rapid physical and psychological development.However relative to the mounting observational and experimental studies in young and elderly adults showing the independent and combination effect of PA and sleep on cognition,only little information regarding association between sleep and PA,and independent and joint associations of sleep and PA on cognition in preschool children.This study mainly includes three parts.Study one,we randomly collected our participants from seven kindergartens located in Yangpu and Baoshan District in Shanghai,China.The study samples consisted of 306 participants.There were 176(57.5%)boys and 130(42.5%)girls.Sleep were assessed by Chinese versions of the Child Behavior Checklist(CBCL),completed by the child’s parent.The questionnaire contains 6 sleep items.Parents answered questions about their child’s experiences within the past 6 months with the following: Doesn’t want to sleep alone(DWSA);Talks or cries out in sleep(ST/C);Nightmares;has trouble getting to sleep(TGS),Wakes up often at night(WUO);Sleeps less than most kids(Sleep less).The cognitive performance was assessed by the simplified version and norms of China-Wechsler Younger Children Scale of Intelligence(C-WYCSI).We selected 2 verbal(information and vocabulary)and 2 performance(block design and picture completion)subtests to comprise the verbal intelligence(VIQ)and performance intelligence(PIQ).Finally,we used these two scores and the simplified version and norms of C-WYCSI to find a composite score that represents a child’s general intellectual ability,the full scale intelligence(FIQ).In order to examine the independent associations between sleep items and IQ scores,we used a series of analysis of covariance(ANCOVA)with each sleep item as a between-subjects factor and gender,age,mother’s education and father’s income as covariates.Study two,physical activity was measured over 7 consecutive days with a triaxial ActiGraph accelerometer model GT3X+ worn on the midaxilla line at the level of iliac crest on an elastic,nylon belt.Data were collected with 1-second epoch,and processed with ActiLife.Participants were ask to ware the accelerometer during the waking hours except for shower,swimming and sleeping.In order to quantify LPA,MPA and VPA from accelerometry output we applied the cut-point described by Pate.In order to examine the independent associations between sleep items and physical activity,we used a series of analysis of covariance(ANCOVA)with each sleep item as a between-subjects factor and age,mother’s education and father’s income as covariates.Study three,MVPA was analyzed as a binary variable separated by the sex-specific median.In order to examine the joint association of sleep items and daily physical activity on cognitive abilities in children,we used a series of multivariate analysis of covariance(MANCOVA)with each sleep item and MVPA as betweensubjects factors and age,mother’s education and father’s income as covariates.The study one demonstrated:There was a total of 282 participants responded at least one question((boys,164;58.2%).The prevalence of sleep problems occurring sometimes/often was 82.1% for DWSA,50.4% for ST/W,45.1% for Nightmares,47.8% for TGS,39.0% for WUO,and 35.2% for Sleep less.For most sleep problems,the prevalence was similar between boys and girls for same problem.However,boys were more likely to have DWSA(86.3% in boys and 76.2% in girls;P = 0.04).The ANCOVA showed that there were significant differences in mean VIQ,PIQ and FIQ scores between preschoolers with and without DWSA.Mean VIQ and FIQ score in children who have DWSA was higher than that of children who did not have the sleep problem,about 2 and 6 points,respectively.These differences were highly significant(F=6.495,P=0.011;F=7.478,P=0.007).Subsequent subgroup analysis with regard to gender showed that boys with DWSA achieved marginally higher mean VIQ,and significant higher mean PIQ(F=5.948,P=0.016)and FIQ(F=5.773,P=0.018)than did the boys without DWSA.Additionally,mean VIQ was significantly higher among girls with DWSA than in the girls without this problem.The study two demonstrated:According to the inclusion criterion,there were a total of 271 participants have the complete data of level of physical activity,which accounted 88.6 percentage of total sample size.There was a total of 256 participants responded at least one question,and have the complete data of basic information(boys,175;57.5%).The ANCOVA showed that,in girls,there was significant difference in mean MPA and MVPA with and without Sleep less.Mean MPA and MVPA time in children who have Sleep less was lower than that of children who did not have the sleep problem,about 3.3min/day and 6.5min/day,respectively(F=6.026,P=0.016;F=5.336,P=0.023).The relation between sleep problems and physical activity was not found in boys.The study three demonstrated:There was a total of 252 participants responded at least one question,and have the complete data of level of PA,cognitive ability tests and basic information(boys,141;56.0%).The results of MANCOVA showed that,in boys,the MVPA was significant correlated with VIQ and FIQ(P<0.05).Mean VIQ and FIQ score in high MVPA group was higher than low MVPA group about 2 to 4 points and 2 to 11 points,respectively.Neither sleep problems nor MVPA was significantly correlated with IQ scores in girls.There was no significant joint associations of sleep problems and moderate-to-vigorous physical activity on IQ scores.The main conclusions of this study include:The preschool children with DWSA was associated with higher cognitive performance.Our findings suggest that co-sleep can benefit the promotion of cognitive development and functioning in preschoolers.In addition,some gender differences were identified in the association between sleep deficits and PA.Girls in the high MVPA group,however,had significantly better cognitive abilities.Finally,the results from our study did not find the joint effect of sleep and PA on cognitive abilities in preschoolers.More powerful study design needed to identify the interaction between sleep and PA for children in the future.