HSE REPORT REVIEWS RESEARCH ON THE RELATIONSHIP BETWEEN SHIFT WORK AND BREAST CANCER

HSE press release: E132:03 - 15 July 2003

The possibility that shift working can increase the potential for women to contract breast cancer needs further study according to a new research report published today by the Health and Safety Executive (HSE).
The research report, 'Shift work and breast cancer: a critical review of the epidemiological evidence' was prepared by Professor Anthony Swerdlow, a leading epidemiologist at the Institute of Cancer Research.
Professor Swerdlow concluded that: "Overall, the evidence for an association is appreciable, but not definitive" and that "further epidemiological research is needed to clarify the relationship."

HSE commissioned this research following the publication of two articles in the Journal of the National Cancer Institute in the United States, which indicated the possibility of a relationship between shift work and breast cancer. These articles suggested that an effect of altered light exposure at night on levels of melatonin or other hormones may affect cancer risk.

In his work for HSE, Professor Swerdlow considered the results of four published epidemiological studies which addressed the possible relationship between breast cancer risk and shift work, and considered other relevant scientific information.

Sandra Caldwell, Co-Director of Policy in HSE said: "Breast disease is a source of anxiety for many women - each year breast cancer is diagnosed in 40,000 women in Great Britain. Many factors are known to increase the risk of breast cancer and it is important that HSE investigates those which might be specifically associated with work activities. However, the behavioural, environmental and genetic risk factors for breast cancer make it particularly difficult to identify how factors like shift work, particularly extended nightshift work, may be involved."

Mrs Caldwell added: "It is very helpful that this review has been done. The review suggests that so far epidemiological research is inconclusive about the link between breast cancer risk and shift work, if any, and further research will be necessary to clarify the relation. To take this forward, the Medical Research Council will convene a group of national and international scientific and medical experts to advise on how the research agenda should be progressed. Their findings will be widely disseminated.

"Without conclusive research, we cannot develop definitive guidance on the risks from nightshift work. However, we recognise that the possibility of contracting breast cancer is a cause of concern for many women. The Government's advice to all women is to be breast aware. They need to know what is normal for them, and tell their doctor without delay if they become aware of any change from normal in their breasts."

Shiftwork and breast cancer: A critical review of the epidemiological evidence. Research Report 132 is available free of charge on the HSE website at http://www.hse.gov.uk/research/rrhtm/index.htm

Notes to editors

1. This report and the work it describes were funded by the HSE, but its contents, including any opinions, are those of the author alone and do not necessarily reflect HSE policy. Professor Swerdlow is Professor of Epidemiology and Director of the Department of Health Cancer Screening Unit at the Institute. Originally educated in Medicine at the Universities of Cambridge and Oxford, Professor Swerdlow holds doctorates in epidemiology from Glasgow, Oxford and London Universities, is a Fellow of the Faculty of Public Health Medicine of the Royal College of Physicians, and is a Fellow of the Academy of Medical Sciences.

2. The idea that shift work might influence breast cancer risk derives from a hypothesis put forward in 1987 that light exposure at night might affect breast cancer risk by a hormonal mechanism.

3. The findings on the relationship of shiftwork to breast cancer risk need to be interpreted in view of the knowledge of existing and suspected risk factors for breast cancer. A major complication in assessing the shift work literature is the possibility that shift work might be a surrogate for one or more established risk factors for breast cancer, including behavioural, environmental and genetic factors. Established risk factors include having no children, late age at birth of first child, starting periods early, late age at menopause, and (large doses of) ionising radiation exposure.

4. Four published studies were identified that directly investigated whether shift work is associated with risk of breast cancer. Each has different methodological strengths and each found some statistically significant associations.

5 The Institute of Cancer Research is one of the world's leading cancer research organisations and is internationally renowned for the quality of its science. Its mission is the relief of human suffering by pursuing excellence in the fight against cancer. The Institute is a College of The University of London. It works in a unique partnership with The Royal Marsden Hospital and together they form Europe's largest comprehensive cancer centre.

6. The Medical Research Council (MRC) promotes research into all areas of medical and related science with the aims of improving the health and quality of life of the UK public and contributing to the wealth of the nation. The MRC is funded by the UK Government and receives an annual Grant in aid from Parliament via the Office of Science and Technology, now part of the Department of Trade and Industry. Working through its Council, scientific boards, and committees, the MRC is independent in its choice of which research to support. It does however work in close partnership with Health Departments, other Research Councils, industry and others to identify and respond to current and future health needs.

7. The draft Terms of Reference of the Expert Advisory Group to be convened by the Medical Research Council are:

• To consider the evidence relating shift work to breast cancer in women and
• To identify what further research is required and how this might best be taken forward.

In the light of the Group's report, HSE, MRC and other relevant stakeholders will consider how the report's recommendations might be implemented.

8. Estimates from the Spring 2002 wave of the Labour Force survey suggest that an estimated 1.8 million women in Great Britain usually or sometimes do shift work. Of these, an estimated 400,000 are involved in night work (night shift, continental shift and three-shift working).

9 In association with Cancer Research UK, NHS Cancer Screening Programmes produce a leaflet giving advice to women on this issue, entitled Be Breast Aware. The leaflet is available in many languages to ensure as many women as possible have the right information. Copies are widely available in GP practices and clinics.

10. HSE is currently consulting new guidance on shiftwork. Some general advice on shiftwork is currently provided on pages 35-37 in chapter 4 of Reducing error and influencing behaviour (HSG48) ISBN 0 7176 2452 8 price £11.50

Press enquiries

All enquiries from journalists should be directed to the HSE Press Office