title: Predicting changes in sleep complaints from baseline values and changes in work demands, work control, and work preoccupation--the WOLF-project.
abstract: OBJECTIVE
  Stress as a cause of disturbed sleep is often taken for granted, but the longitudinal evidence is limited. The aim of this study was to evaluate new cases of poor sleep as a function of changes in reported work demands, work control, and work preoccupation.
  
  
  METHODS
  Longitudinal study of change with measures occurring twice within a 5-year interval during a period when the prevalence of impaired sleep was increasing in Sweden. The sample of companies was taken from northern Sweden (Norrland) and included 3637 individuals from the "WOLF Norrland" longitudinal cohort, collected through company health services.
  
  
  RESULTS
  During the measurement period, 16% of those studied developed new cases of impaired sleep. Logistic regressions adjusted for demographics, work environment factors, and disturbed sleep at T1 period one showed a significant increase in new cases for high work demands and high work preoccupation (OR=1.37; Ci=1.09-1.72 and OR=1.80; CI=1.42-2.28, respectively). The analysis of change in the predictors showed effects of a change from low to high work demands (OR=1.39; Ci=1.00-1.95) on new cases of impaired sleep. Consistent high work demands (high at both points) showed a similar increase (OR=1.49; Ci=1.06-2.11) but no effect was seen for reduced demands. Change in work preoccupation yielded stronger effects with OR=2.47 (1.78-2.47) for increased work preoccupation and OR=3.79 (2.70-5.31) for consistent high work preoccupation. Also, a reduction in work preoccupation was associated with a reduction in new cases of disturbed sleep. Control at work was not related to sleep. Stratification with respect to gender mainly led to fewer significant results (particularly for women) due to larger confidence intervals.
  
  
  CONCLUSIONS
  It was concluded that self-reported work preoccupation predicts subsequent impairment of sleep and that increased preoccupation is associated with new cases of impaired sleep. Similar, but weaker, results were obtained for work demands.
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden. torbjorn.akerstedt@stress.su.se
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Åkerstedt
authors.forename: Maria
authors.initials: M
authors.lastname: Nordin
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.forename: Peter
authors.initials: P
authors.lastname: Westerholm
authors.forename: Göran
authors.initials: G
authors.lastname: Kecklund
mesh_terms: D000328:Adult; D004651:Employment / Q000523:psychology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D017533:Marital Status; D008875:Middle Aged; D012890:Sleep; D012893:Sleep Wake Disorders / Q000453:epidemiology / Q000209:etiology*; D012959:Socioeconomic Factors; D013315:Stress, Psychological / Q000150:complications / Q000453:epidemiology; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D016526:Workload / Q000523:psychology* / Q000706:statistics & numerical data