The results of a study published last week in the journal of Occupational & Environmental Medicine has added to the growing body of evidence that night shift work is associated with breast cancer.

The authors, from the Institute of Cancer Epidemiology of the Danish Cancer Society, conducted a nationwide case-control study of almost 19,000 female military employees born over the period 1929 to 1968. They investigated the risk for breast cancer for night shift workers along with other risk factors.

Not surprisingly, perhaps, they found that the risk tended to increase the longer the women did night shift work and with the number of shifts they did, although it found a neutral risk for women working fewer than three night shifts per week.

These results build on work carried out by Imperial College London on behalf of the Health and Safety Executive (HSE). It reported in 2010 that an estimated 2000 breast cancer cases and around 550 breast cancer deaths a year could be attributable to shift work.

The HSE has commissioned the University of Oxford to undertake an extensive study on the relationship between shift work and chronic disease, with a focus on shift working patterns in relation to cancer and other chronic conditions in men and women. The study will be completed by December 2015.

The International Agency for Research on Cancer reported as long ago as 2007 that it had found a higher risk of breast cancer among long-term nightworkers compared to women who did not work at night.

TUC General Secretary Brendan Barber commented that:

'This study confirms previous research which has shown that shift work is now the second biggest cause of work-related cancer deaths after asbestos.

'We need urgent advice from the HSE and government so that employers can reduce the risk of female workers developing breast cancer, for example by indentifying safer shift patterns.'

Click the link to access the study (pdf 104KB)