title: Individual and gender differences matter in preterm infant state development.
abstract: OBJECTIVE
  To further understand state development of preterm infants throughout hospitalization and the effects of selected infant characteristics on state development.
  
  
  METHODS
  Secondary data analysis of a 2-group, experimental design study.
  
  
  METHODS
  Two nurseries in a Northwest medical center.
  
  
  METHODS
  Ninety-seven hospitalized, medically stable, preterm infants. Fifty-one subjects were females.
  
  
  METHODS
  Two hundred and eighty-five real-time video recordings of infants performed during 4 hour interfeeding intervals. Sleep-wake states were coded at 15 second intervals.
  
  
  RESULTS
  Active sleep was the dominant state across postmenstrual ages. Although not statistically significant, preterm infants showed developmental changes in state organization with increased quiet sleep, drowsy, and awake, decreased active sleep, and more defined and less diffuse states over age. A significant gender effect was found, with males having less active sleep (p=.012), more drowsy (p=.03), more awake (p=.043), less defined (p=.002), and more diffuse (p=.001) states compared with females.
  
  
  CONCLUSIONS
  The predominance of active sleep during the preterm period reflects level of brain maturation. The results emphasize individual variations in state organization influenced by endogenous and environmental factors. Gender differences are potential sources of individual variation.
authors.affiliation: Department of Family and Child Nursing and Biobehavioral Nursing and Health Systems, University of Washington, Seattle, WA 98195-7266, USA. yuann@u.washington.edu
authors.forename: Shuyuann Wang
authors.initials: SW
authors.lastname: Foreman
authors.forename: Karen A
authors.initials: KA
authors.lastname: Thomas
authors.forename: Susan T
authors.initials: ST
authors.lastname: Blackburn
mesh_terms: D000704:Analysis of Variance; D001724:Birth Weight; D016009:Chi-Square Distribution; D015400:Clinical Nursing Research; D005247:Feeding Behavior / Q000502:physiology / Q000523:psychology; D005260:Female; D005865:Gestational Age; D006801:Humans; D007206:Individuality; D018730:Infant Behavior / Q000502:physiology / Q000523:psychology; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology / Q000523:psychology; D015931:Intensive Care, Neonatal; D016014:Linear Models; D008297:Male; D015205:Northwestern United States; D012727:Sex Characteristics; D012890:Sleep / Q000502:physiology; D013997:Time Factors; D014743:Videotape Recording; D014851:Wakefulness / Q000502:physiology