title: Does night work increase the risk of breast cancer? A systematic review and meta-analysis of epidemiological studies.
abstract: OBJECTIVE
  To conduct a systematic review, with meta-analysis, of studies assessing the association between night work and the risk of breast cancer, using available epidemiological evidence.
  
  
  METHODS
  Relevant studies were identified by searching several databases and the reference lists of retrieved articles. We combined the relative risks (RR) from individual studies using a random-effects model. Subgroup analysis was carried out as the data showed statistically significant heterogeneity.
  
  
  RESULTS
  Thirteen studies consisting of eight case-control studies and five cohort studies were included in the analysis. In the combined analysis of all studies, night work was associated with an increased risk for breast cancer (RR = 1.20, 95%CI = 1.08-1.33). The higher-quality studies showed a similar finding with a pooled RR of 1.40 (95%CI = 1.13-1.73). Both case-control studies (RR = 1.32, 95%CI = 1.17-1.50) and cohort studies (RR=1.08, 95%CI = 0.97-1.21) showed a positive association between night work and the risk of breast cancer. No publication bias was found either from Begg's funnel plot (P = 0.086) or the Egger's test (P = 0.107). Additional well-conducted and large-scale epidemiological studies are needed.
authors: Department of General Surgery, XinHua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200092, China.
authors: Yijun
authors: Y
authors: Jia
authors: Yunshu
authors: Y
authors: Lu
authors: Kejin
authors: K
authors: Wu
authors: Qing
authors: Q
authors: Lin
authors: Wei
authors: W
authors: Shen
authors: Mingjie
authors: M
authors: Zhu
authors: Shuo
authors: S
authors: Huang
authors: Jian
authors: J
authors: Chen
mesh_terms: D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D002940:Circadian Rhythm; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D012307:Risk Factors; D014940:Work Schedule Tolerance