The association between different night shiftwork factors and breast cancer: a case-control study

Br J Cancer. 2013 Oct 29;109(9):2472-80. doi: 10.1038/bjc.2013.544. Epub 2013 Sep 10.

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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Breast Neoplasms / epidemiology*
  • Breast Neoplasms / etiology
  • Case-Control Studies
  • Female
  • Humans
  • Life Style
  • Middle Aged
  • Risk
  • Risk Factors
  • Surveys and Questionnaires
  • Western Australia / epidemiology
  • Work Schedule Tolerance*
  • Young Adult