title: Bright-light effects on cognitive performance in elderly persons working simulated night shifts: psychological well-being as a mediator?
abstract: OBJECTIVE
  The present study examined whether the relationship between light exposure and cognitive functioning is mediated by psychological well-being in elderly persons working night shifts. The role of psychological well-being has been neglected so far in the relationship between bright light and cognitive performance. Sleepiness and mood were applied as indicators of psychological well-being. Cognitive functioning was examined in terms of concentration, working memory, and divided attention.
  
  
  METHODS
  A total of thirty-two test persons worked in three consecutive simulated night shifts, 16 under bright light (3,000 lux) and 16 under room light (300 lux). Concentration, working memory, and divided attention were measured by computerised tasks. The hypothesised mediators were recorded by questionnaires.
  
  
  RESULTS
  Mediation analyses were conducted for estimating direct, total, and indirect effects in simple mediation models. Results indicate that sleepiness and mood did not function as mediators in the prediction of concentration, working memory, and/or divided attention by light exposure.
  
  
  CONCLUSIONS
  Sleepiness led to an underestimation of the positive bright-light effect on concentration performance. Mood showed only a random effect due to the positive bright-light effect on working memory. Sleepiness and mood could completely be excluded as mediators in the relationship between light exposure and cognitive functioning. This study underlines that psychological well-being of elderly persons is not a critical component in the treatment of bright light on cognitive performance in the night shift workplace. In summary, it becomes evident that bright light has a strong direct and independent effect on cognitive performance, particularly on working memory and concentration.
authors.affiliation: Leibniz Research Centre for Working Environment and Human Factors at the TU Dortmund, Ardeystr. 67, 44139, Dortmund, Germany, kretschmer@ifado.de.
authors.forename: Veronika
authors.initials: V
authors.lastname: Kretschmer
authors.forename: Klaus-Helmut
authors.initials: KH
authors.lastname: Schmidt
authors.forename: Barbara
authors.initials: B
authors.lastname: Griefahn
mesh_terms: D000339:Affect; D000368:Aged; D001288:Attention; D006970:Disorders of Excessive Somnolence / Q000523:psychology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008568:Memory; D008603:Mental Health; D008875:Middle Aged; D016273:Occupational Exposure; D013647:Task Performance and Analysis; D014940:Work Schedule Tolerance / Q000523:psychology*