title: The association between different night shiftwork factors and breast cancer: a case-control study.
abstract: BACKGROUND
  Research on the possible association between shiftwork and breast cancer is complicated because there are many different shiftwork factors, which might be involved including: light at night, phase shift, sleep disruption and changes in lifestyle factors while on shiftwork (diet, physical activity, alcohol intake and low sun exposure).
  
  
  METHODS
  We conducted a population-based case-control study in Western Australia from 2009 to 2011 with 1205 incident breast cancer cases and 1789 frequency age-matched controls. A self-administered questionnaire was used to collect demographic, reproductive, and lifestyle factors and lifetime occupational history and a telephone interview was used to obtain further details about the shiftwork factors listed above.
  
  
  RESULTS
  A small increase in risk was suggested for those ever doing the graveyard shift (work between midnight and 0500 hours) and breast cancer (odds ratio (OR)=1.16, 95% confidence interval (CI)=0.97-1.39). For phase shift, we found a 22% increase in breast cancer risk (OR=1.22, 95% CI=1.01-1.47) with a statistically significant dose-response relationship (P=0.04). For the other shiftwork factors, risks were marginally elevated and not statistically significant.
  
  
  CONCLUSIONS
  We found some evidence that some of the factors involved in shiftwork may be associated with breast cancer but the ORs were low and there were inconsistencies in duration and dose-response relationships.
authors.affiliation: Western Australian Institute for Medical Research, The University of Western Australia, Nedlands, Western Australia, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Fritschi
authors.forename: T C
authors.initials: TC
authors.lastname: Erren
authors.forename: D C
authors.initials: DC
authors.lastname: Glass
authors.forename: J
authors.initials: J
authors.lastname: Girschik
authors.forename: A K
authors.initials: AK
authors.lastname: Thomson
authors.forename: C
authors.initials: C
authors.lastname: Saunders
authors.forename: T
authors.initials: T
authors.lastname: Boyle
authors.forename: S
authors.initials: S
authors.lastname: El-Zaemey
authors.forename: P
authors.initials: P
authors.lastname: Rogers
authors.forename: S
authors.initials: S
authors.lastname: Peters
authors.forename: T
authors.initials: T
authors.lastname: Slevin
authors.forename: A
authors.initials: A
authors.lastname: D'Orsogna
authors.forename: F
authors.initials: F
authors.lastname: de Vocht
authors.forename: R
authors.initials: R
authors.lastname: Vermeulen
authors.forename: J S
authors.initials: JS
authors.lastname: Heyworth
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D012306:Risk; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014904:Western Australia / Q000453:epidemiology; D014940:Work Schedule Tolerance; D055815:Young Adult
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