title: Natural light exposure, sleep and depression among day workers and shiftworkers at arctic and equatorial latitudes.
abstract: OBJECTIVE
  This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.
  
  
  METHODS
  This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).
  
  
  RESULTS
  The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.
  
  
  CONCLUSIONS
  Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.
authors: Department of Environmental Health, School of Public Health-University of Sao Paulo, USP, Sao Paulo, Sao Paulo, Brazil; Stress Research Institute, Stockholm University, Stockholm, Sweden; Epidemiology, Public Health Graduate Program-Catholic University of Santos, UNISANTOS, Santos, Sao Paulo, Brazil.
authors: Elaine Cristina
authors: EC
authors: Marqueze
authors: Department of Environmental Health, School of Public Health-University of Sao Paulo, USP, Sao Paulo, Sao Paulo, Brazil; Science's Health Department, Federal University of Acre, UFAC, Rio Branco, Acre, Brasil.
authors: Suleima
authors: S
authors: Vasconcelos
authors: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Johanna
authors: J
authors: Garefelt
authors: Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, United Kingdom.
authors: Debra J
authors: DJ
authors: Skene
authors: Department of Environmental Health, School of Public Health-University of Sao Paulo, USP, Sao Paulo, Sao Paulo, Brazil; Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Claudia Roberta
authors: CR
authors: Moreno
authors: Stress Research Institute, Stockholm University, Stockholm, Sweden.
authors: Arne
authors: A
authors: Lowden
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001110:Arctic Regions; D001938:Brazil; D002940:Circadian Rhythm / Q000502:physiology; D003430:Cross-Sectional Studies; D003863:Depression / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D008027:Light; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012621:Seasons; D012890:Sleep / Q000502:physiology*; D013548:Sweden; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000502:physiology* / Q000523:psychology; D055815:Young Adult