New study debunks link between night shifts and breast cancer risk

6 October 2016

A new study has offered evidence disputing a previously assumed link between night shift work and an elevated risk of breast cancer in women.

The Oxford University research built on previous analysis from the World Health Organization indicating that shift work involving a disruption of the circadian rhythm was a probable carcinogen.

For this new study, a total of 800,000 women were followed in three large UK studies, with the relative risks of breast cancer estimated among women who reported night shift work versus those who did not.

No increase in breast cancer risk associated with night shift work, including long-term night shifts, was found in any of these studies. Similar results were seen when factoring in the conclusions of seven prior studies from the US, China, Sweden and the Netherlands, which included 1.4 million women in total.

It was noted that previous research was based on evidence about breast cancer in animal studies, as there was only limited evidence about human breast cancer risk at the time.

Dr Ruth Travis of the Cancer Epidemiology Unit at Oxford University said: "We found that women who had worked night shifts ... were not more likely to develop breast cancer, either in the three new UK studies or when we combined results from all ten studies that had published relevant data."

Posted by Jeanette Royston


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