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

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

L Fritschi  1 , T C Erren, D C Glass, J Girschik, A K Thomson, C Saunders, T Boyle, S El-Zaemey, P Rogers, S Peters, T Slevin, A D'Orsogna, F de Vocht, R Vermeulen, J S Heyworth
Affiliations

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

L Fritschi et al. Br J Cancer. .

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.

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