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Breast cancer and shift work

by Henry Scowcroft | Analysis

16 March 2009

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London at night.

This article is more than 3 years old. For a more recent picture, read our latest article on night shifts and breast cancer

Yesterday the Danish government announced that it would compensate women who had spent long periods working nights, and who went on to develop breast cancer.

The ruling comes a year after the the International Association for Research on Cancer weighed the evidence around shift-work and, somewhat surprisingly, concluded that there was ‘probably’ a link to breast cancer.

Ed posted a while ago about the strength of this evidence and, to summarise, there does appear to be a statistical link.

But, in our opinion, the studies to date are unclear as to whether shift work actually causes breast cancer, in and of itself, or whether shift workers are more likely do other things that increase their risk, like being inactive or overweight.

One cause or many?

It’s natural, when faced with a diagnosis of cancer, to want be able to point the finger at a single factor in our past as the ’cause’ of the disease. But cancer is complicated. Rather than a single cause, it’s best thought of as being the result of many factors, all of which make a small but significant contribution.

For breast cancer, these factors include a woman’s genes, her age, her weight, her race, how much she drinks, when she started (and stopped) her periods, how many children she had, whether (and for how long) she took the Pill or HRT, and how long she breast-fed.

The big question is – how do all these factors affect each other? It’s a picture that, here at Cancer Research UK and around the world, scientists are striving hard to clarify.

Ongoing research

Back to the question of shift work. In any situation where a person’s job is proven to significantly affect their risk of disease, they should be entitled to help and support in the event that they develop that disease.

The UK’s Health and Safety Executive, in a 2003 report, stated:

The complex mixture of causes, the close relations of several of them with general lifestyle, and the wide range of ages at which they act, make it particularly difficult to deal with confounding when examining relations to new postulated causal factors such as shift work.

They’ve commissioned addition research to answer some of these questions, which is due to publish in 2011.

This research should help the UK government determine whether compensation is necessary in the case of shift work and cancer.

In the mean time, it’s important to be breast aware, to see your GP straight away if you notice anything unusual, and always take up invitations to go for breast screening.

And remember that keeping a healthy weight after the menopause, cutting down on alcohol and being active can all help reduce your risk of breast cancer, as well as other diseases.