title: Temporal associations between daytime physical activity and sleep in children.
abstract: OBJECTIVE
  We examined temporal associations between objectively-measured physical activity (PA) during the day and in the evening, and sleep quantity and quality.
  
  
  METHODS
  PA and sleep were measured by actigraphs for an average of one week in an epidemiological cohort study of 275 eight-year-old children.
  
  
  RESULTS
  For each one standard deviation (SD) unit of increased PA during the day, sleep duration was decreased by 0.30, sleep efficiency by 0.16, and sleep fragmentation increased by 0.08 SD units that night. For each one SD unit increase in sleep duration and efficiency the preceding night, PA the following day decreased by 0.09 and 0.16 SD units, respectively. When we contrasted days with a high amount of moderate to vigorous activity during the day or in the evening to days with a more sedentary profile, the results were essentially similar. However, moderate to vigorous PA in the evening shortened sleep latency.
  
  
  CONCLUSIONS
  The relationship between a higher level of PA and poorer sleep is bidirectional. These within-person findings challenge epidemiological findings showing that more active people report better sleep. Since only a few studies using objective measurements of both PA and sleep have been conducted in children, further studies are needed to confirm/refute these results.
authors: Faculty of Behavioral Sciences, Institute of Behavioral Sciences, University of Helsinki, Helsinki, Finland. Anukatriina.pesonen@helsinki.fi
authors: Anu-Katriina
authors: AK
authors: Pesonen
authors: Noora M
authors: NM
authors: Sjöstén
authors: Karen A
authors: KA
authors: Matthews
authors: Kati
authors: K
authors: Heinonen
authors: Silja
authors: S
authors: Martikainen
authors: Eero
authors: E
authors: Kajantie
authors: Tuija
authors: T
authors: Tammelin
authors: Johan G
authors: JG
authors: Eriksson
authors: Timo
authors: T
authors: Strandberg
authors: Katri
authors: K
authors: Räikkönen
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology*; D012890:Sleep / Q000502:physiology*; D013997:Time Factors