title: Shift work at young age is associated with increased risk for multiple sclerosis.
abstract: OBJECTIVE
  Environmental factors play a prominent role in multiple sclerosis (MS) etiology. The aim of this study was to investigate the potential association between shift work and MS risk, which has previously never been investigated.
  
  
  METHODS
  This report is based on 2 population-based, case-control studies, 1 with incident cases (1,343 cases, 2,900 controls) and 1 with prevalent cases (5,129 cases, 4,509 controls). Using logistic regression, the occurrence of MS among subjects who have been exposed to shift work at various ages was compared with that of those who have never been exposed by calculating the odds ratio (OR) with a 95% confidence interval (CI).
  
  
  RESULTS
  In both studies, there was a significant association between working shift at a young age and occurrence of MS (OR, 1.6; 95% CI, 1.2-2.1 in the incidence study and OR, 1.3; 95% CI, 1.0-1.6 in the prevalence study). In the incident study, the OR of developing MS was 2.0 (95% CI, 1.2-3.6) among those who had worked shifts for 3 years or longer before age 20 years, compared with those who had never worked shifts. The OR for the corresponding comparison in the prevalent study was 2.1 (95% CI, 1.3-3.4).
  
  
  CONCLUSIONS
  The observed association between shift work at a young age and occurrence of MS in 2 independent studies strengthens the notion of a true relationship. Consequences of shift work such as circadian disruption and sleep restriction are associated with disturbed melatonin secretion and enhanced proinflammatory responses and may thus be part of the mechanism behind the association.
authors: Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden. anna.hedstrom@ki.se
authors: Anna Karin
authors: AK
authors: Hedström
authors: Torbjörn
authors: T
authors: Åkerstedt
authors: Jan
authors: J
authors: Hillert
authors: Tomas
authors: T
authors: Olsson
authors: Lars
authors: L
authors: Alfredsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology*; D012307:Risk Factors; D012890:Sleep; D012892:Sleep Deprivation; D011795:Surveys and Questionnaires; D055815:Young Adult