title: Norms and trends of sleep time among US children and adolescents.
abstract: OBJECTIVE
  To develop national sleep norms conditional on age and to examine stratification by sex, race/ethnicity, and changes over time.
  
  
  METHODS
  Secondary analysis of a panel survey.
  
  
  METHODS
  The 3 waves (1997, 2002, and 2007) of the Child Development Supplement of the Panel Study of Income Dynamics, a nationally representative survey.
  
  
  METHODS
  Children from birth to 18 years with time-diary data were included: 2832 children in 1997, 2520 children in 2002, and 1424 children in 2007.
  
  
  METHODS
  Age.
  
  
  METHODS
  Minutes of sleep for daytime and total sleep.
  
  
  RESULTS
  The 10th, 25th, 50th, 75th, and 90th percentiles of the distribution of children's minutes of sleep conditional on age were estimated using a double-kernel estimator that incorporates sample weights. Total average sleep was estimated at more than 13 hours a day for infants, decreasing steadily throughout childhood and early adolescence, reaching about 9 hours a day for 14- to 18-year-olds. The estimated conditional percentiles were higher on weekends than on weekdays for older children. The conditional percentiles for the weekend sleep minutes were flatter with respect to age than the weekday sleep minutes. The interquartile ranges were greater for children younger than 6 years and for teenagers. The medians stratified by race/ethnicity and sex were similar for most ages. For different survey years, the estimated medians were within a few minutes of each other.
  
  
  CONCLUSIONS
  These estimates are consistent with the amount of sleep recommended for children, and no evidence was found of racial/ethnic differences.
authors: Department of Health Policy and Management, Fielding School of Public Health, UCLA, Los Angeles, CA 90024, USA. jarw@ucla.edu
authors: Jessica A
authors: JA
authors: Williams
authors: Frederick J
authors: FJ
authors: Zimmerman
authors: Janice F
authors: JF
authors: Bell
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D005006:Ethnicity; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D044469:Racial Groups; D012016:Reference Values; D017678:Sex Distribution; D012890:Sleep; D013997:Time Factors; D014481:United States
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