title: Trends in short and long sleep in Denmark from 1964 to 2009, and the associations with employment, SES (socioeconomic status) and BMI.
abstract: OBJECTIVE
  The aim of the present study was to investigate changes in the prevalence of short and long sleepers in Denmark, and to explore the associations between socioeconomic status, body mass index and sleep duration.
  
  
  BACKGROUND
  Sleeping behavior is considered to be a risk factor for morbidity and mortality, but there is little information on population sleep in Denmark; however, it is suspected that sleep durations have declined over time.
  
  
  METHODS
  Data were used from five Danish population-representative time-use studies spanning 1964-2008/09.
  
  
  RESULTS
  The proportion of short sleepers increased significantly until the end of the 1980s, whereafter it decreased significantly. The proportion of long sleepers reached a maximum in 1975. It was also found that the increase in women's employment rates was associated with half the decrease in their sleep duration over the last 45 years. In accordance with previous literature, it can be shown that both short and long sleep are associated with being overweight/obesity.
  
  
  CONCLUSIONS
  In Denmark, the same number of hours is slept today as in the mid-1960s, with nearly the same prevalence of short and long sleepers.
authors: Rockwool Foundation Research Unit, Copenhagen, Denmark. Electronic address: jb@rff.dk.
authors: Jens
authors: J
authors: Bonke
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003718:Denmark / Q000453:epidemiology; D004651:Employment / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012621:Seasons; D012737:Sex Factors; D012893:Sleep Wake Disorders / Q000453:epidemiology*; D012923:Social Class; D012959:Socioeconomic Factors; D013997:Time Factors; D055815:Young Adult
keywords: Denmark; Public health; Sleep duration; Time-use studies; Trends