Journal scan

No link between breast cancer and working night shifts, researchers say

Working night shifts has little or no effect on a woman’s risk of developing breast cancer, say UK researchers
no connection

Working night shifts has little or no effect on a womans risk of developing breast cancer, say UK researchers.

A 2007 review by the International Agency for Research on Cancer classified shift work as a probable cause of cancer, because it disrupts the body clock.

But new research followed 1.4 million women across 10 studies, including a combination of new results and older data from the United States, China, Sweden and the Netherlands.

Funded by the UK Health and Safety Executive, Cancer Research UK and the UK Medical Research Council, the study represents the largest of its kind.

Researchers found the incidence of breast cancer was essentially the same whether someone did no night shift work at all or worked night shifts for several decades.

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Working night shifts has little or no effect on a woman’s risk of developing breast cancer, say UK researchers.

A 2007 review by the International Agency for Research on Cancer classified shift work as a probable cause of cancer, because it disrupts the body clock. 


New research has shown there is no link between breast cancer
and working night shifts. Picture: Alamy

But new research followed 1.4 million women across 10 studies, including a combination of new results and older data from the United States, China, Sweden and the Netherlands. 

Funded by the UK Health and Safety Executive, Cancer Research UK and the UK Medical Research Council, the study represents the largest of its kind.

Researchers found the incidence of breast cancer was essentially the same whether someone did no night shift work at all or worked night shifts for several decades.

The combined relative risks were 0.99 for any night shift work, 1.01 for 20 or more years of night shift work, and 1.00 for 30 or more years of working nights. 

Cancer Research UK health information manager Sarah Williams said the study ‘found no link between breast cancer and working night shifts'. 

She adds: ‘Research over the past years suggesting there was a link has made big headlines. We hope that today’s news reassures women who work night shifts.’


Travis et al (2016). Night shift work and breast cancer incidence: three prospective studies and meta-analysis of published studies. Journal of the National Cancer Institute. doi: 10.1093/jnci/djw169

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