title: Sleep duration, illumination, and activity patterns in a population sample: effects of gender and ethnicity.
abstract: BACKGROUND
  Current knowledge of the population's sleep durations emanates primarily from questionnaires and laboratory studies. Using Actillumes, we investigated whether self-reported sleep durations were indicative of a population decline in sleep duration. We also explored illumination and activity patterns.
  
  
  METHODS
  San Diego adults (n = 273, age range: 40-64) were recruited through random telephone calls and were monitored at home while engaging in usual daily routines.
  
  
  RESULTS
  Volunteers slept an average of 6.22 hours and received an average of 554 lux (environmental illumination). The timing of sleep, illumination, and activity occurred at 2:44, 12:57, and 13:43, respectively. Irrespective of ethnicity, age, and time reference, men received greater illumination than did women, but this gender effect was not independent of work status. Women and men exhibited a similar circadian activity profile; however, women exhibited better sleep-wake patterns. Interactions between gender and ethnicity suggested worse sleep-wake patterns among minority men. An age-related decline in activity was found, but no age trend in sleep duration or illumination patterns was observed.
  
  
  CONCLUSIONS
  This study showed an objective population decline in sleep duration. Sociodemographic effects should be considered in analyses of sleep-wake patterns and illumination exposures.
authors.affiliation: Department of Psychiatry, University of California San Diego, San Diego, California 92093-0667, USA.
authors.forename: G
authors.initials: G
authors.lastname: Jean-Louis
authors.forename: D F
authors.initials: DF
authors.lastname: Kripke
authors.forename: S
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: M R
authors.initials: MR
authors.lastname: Klauber
authors.forename: R S
authors.initials: RS
authors.lastname: Sepulveda
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology; D005006:Ethnicity; D005260:Female; D006802:Human Activities; D006801:Humans; D008027:Light; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology