title: [Night work, shift work: Breast cancer risk factor?].
abstract: OBJECTIVE
  The aim of this review was to determine the link between night/shift work and breast cancer.
  
  
  METHODS
  The analysed articles were taken from the PUBMED database between 1996 and 2015. The keywords used were "breast cancer risk", "night work" and "shift work". In total, 25 articles were selected.
  
  
  RESULTS
  Night/shift workers are more at risk to develop a breast cancer (relative risk (RR) between 1.09; 95% CI: 1.02-1.20 and 1.48; 95% CI: 1.36-1.61 in the meta-analyses). However, this risk is not found by some cohort and case-control studies. The circadian rhythm disruption, responsible of disorderliness of melatonin secretion, could be one of the mechanisms involved in the increase of that risk. Hormonal status of night/shift workers, their geographic origin, their lifestyle and their vitamin D deficiency appear as other mechanisms potentially responsible for increased risk of cancer in this professional population. Moreover, a dose-effect connection may exist, with an increase of the risk with the number of years of night/shift work.
  
  
  CONCLUSIONS
  Night/shift work is associated with a moderate increased risk of breast cancer, especially among women who worked over 20 years. Recommendations concerning the breast monitoring in this population could be diffused. The benefit of melatonin supplementation remains to be assessed.
authors.affiliation: Pôle de gynécologie-obstétrique, CHRU de Strasbourg, avenue Molière, 67200 Strasbourg cedex, France. Electronic address: juliecharlotte.benabu@chru-strasbourg.fr.
authors.forename: J-C
authors.initials: JC
authors.lastname: Benabu
authors.affiliation: Pôle de gynécologie-obstétrique, CHRU de Strasbourg, avenue Molière, 67200 Strasbourg cedex, France.
authors.forename: F
authors.initials: F
authors.lastname: Stoll
authors.affiliation: Service de pathologie professionnelle et médecine du travail, CHRU de Strasbourg, 67092 Strasbourg cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Gonzalez
authors.affiliation: Unité de sénologie, CHRU de Strasbourg, avenue Molière, 67200 Strasbourg cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Mathelin
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008550:Melatonin / Q000378:metabolism; D015201:Meta-Analysis as Topic; D012307:Risk Factors; D014940:Work Schedule Tolerance
chemical_list: D008550:Melatonin
keywords: Breast cancer risk; Melatonin; Mélatonine; Night work; Risque de cancer du sein; Shift work; Travail de nuit; Travail posté