title: Shift work influences multiple sclerosis risk.
abstract: BACKGROUND
  An association between working shift at a young age and subsequent risk for multiple sclerosis (MS) has been observed.
  
  
  OBJECTIVE
  To investigate whether this finding could be replicated, and to further explore the influence of age at first exposure to shift work.
  
  
  METHODS
  Using a Swedish population-based, case-control study (2337 cases and 4904 controls), the incidence of MS among subjects whom had worked shifts was compared with that of those whom had not, by calculating odds ratios (ORs) with 95% confidence intervals (CIs) by means of logistic regression.
  
  
  RESULTS
  The OR of developing MS was 1.5 (95% CI 1.2-1.8) among those whom started working shifts before age 20, whereas a less pronounced association was observed among those whom started working shifts at age 20 or later (OR 1.2; 95% CI 1.1-1.4). The effect of shift work was more pronounced among subjects whom had been exposed at a young age, regardless of the duration between the start of shift work and disease onset.
  
  
  CONCLUSIONS
  Some aspects of adolescence seem to be of great importance, regarding the impact of shift work on MS risk. Circadian disruption and sleep deprivation may contribute towards explaining the association; however, the exact mechanisms behind our observations remain to be elucidated.
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden anna.hedstrom@ki.se.
authors.forename: A K
authors.initials: AK
authors.lastname: Hedström
authors.affiliation: Stress Research, Stockholm University, Sweden/ Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Åkerstedt
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden/Center for Molecular Medicine, Karolinska University Hospital, Karolinska Institutet, Solna, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Olsson
authors.affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Alfredsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology*; D016017:Odds Ratio; D012307:Risk Factors; D014940:Work Schedule Tolerance; D055815:Young Adult
keywords: Adolescence; circadian rhythm; immunology; multiple sclerosis; risk factors; shift work; sleep deprivation; work schedule