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Cancer incidence and mortality in relation to body mass index in the Million Women Study: cohort study

BMJ 2007; 335 doi: (Published 29 November 2007) Cite this as: BMJ 2007;335:1134
  1. Gillian K Reeves, statistical epidemiologist,
  2. Kirstin Pirie, statistician,
  3. Valerie Beral, director,
  4. Jane Green, clinical research scientist,
  5. Elizabeth Spencer, nutritionist,
  6. Diana Bull, senior statistician
  7. Million Women Study Collaboration
  1. Cancer Epidemiology Unit, University of Oxford, Oxford OX3 7LF
  1. Correspondence to: G Reeves gill.reeves{at}
  • Accepted 5 October 2007


Objective To examine the relation between body mass index (kg/m2) and cancer incidence and mortality.

Design Prospective cohort study.

Participants 1.2 million UK women recruited into the Million Women Study, aged 50-64 during 1996-2001, and followed up, on average, for 5.4 years for cancer incidence and 7.0 years for cancer mortality.

Main outcome measures Relative risks of incidence and mortality for all cancers, and for 17 specific types of cancer, according to body mass index, adjusted for age, geographical region, socioeconomic status, age at first birth, parity, smoking status, alcohol intake, physical activity, years since menopause, and use of hormone replacement therapy.

Results 45 037 incident cancers and 17 203 deaths from cancer occurred over the follow-up period. Increasing body mass index was associated with an increased incidence of endometrial cancer (trend in relative risk per 10 units=2.89, 95% confidence interval 2.62 to 3.18), adenocarcinoma of the oesophagus (2.38, 1.59 to 3.56), kidney cancer (1.53, 1.27 to 1.84), leukaemia (1.50, 1.23 to 1.83), multiple myeloma (1.31, 1.04 to 1.65), pancreatic cancer (1.24, 1.03 to 1.48), non-Hodgkin's lymphoma (1.17, 1.03 to 1.34), ovarian cancer (1.14, 1.03 to 1.27), all cancers combined (1.12, 1.09 to 1.14), breast cancer in postmenopausal women (1.40, 1.31 to 1.49) and colorectal cancer in premenopausal women (1.61, 1.05 to 2.48). In general, the relation between body mass index and mortality was similar to that for incidence. For colorectal cancer, malignant melanoma, breast cancer, and endometrial cancer, the effect of body mass index on risk differed significantly according to menopausal status.

Conclusions Increasing body mass index is associated with a significant increase in the risk of cancer for 10 out of 17 specific types examined. Among postmenopausal women in the UK, 5% of all cancers (about 6000 annually) are attributable to being overweight or obese. For endometrial cancer and adenocarcinoma of the oesophagus, body mass index represents a major modifiable risk factor; about half of all cases in postmenopausal women are attributable to overweight or obesity.


  • We thank the women who participated in the Million Women Study and Adrian Goodill for preparation of the figures.

  • Million Women Study Steering Committee: Joan Austoker, Emily Banks, Valerie Beral, Judith Church, Ruth English, Julietta Patnick, Richard Peto, Gillian Reeves, Martin Vessey, Matthew Wallis.

    Million Women Study Coordinating Centre staff: Simon Abbott, Krys Baker, Angela Balkwill, Sue Bellenger, Valerie Beral, Judith Black, Anna Brown, Diana Bull, Delphine Casabonne, Barbara Crossley, Dave Ewart, Sarah Ewart, Lee Fletcher, Toral Gathani, Laura Gerrard, Adrian Goodill, Jane Green, Winifred Gray, Joy Hooley, Sau Wan Kan, Carol Keene, Nicky Langston, Bette Liu, Sarit Nehushtan, Lynn Pank, Kirstin Pirie, Gillian Reeves, Andrew Roddam, Emma Sherman, Moya Simmonds, Elizabeth Spencer, Richard Stevens, Helena Strange, Sian Sweetland, Aliki Taylor, Alison Timadjer, Sarah Tipper, Joanna Watson, Stephen Williams.

    Collaborating UK NHS breast screening centres: Avon, Aylesbury, Barnsley, Basingstoke, Bedfordshire and Hertfordshire, Cambridge and Huntingdon, Chelmsford and Colchester, Chester, Cornwall, Crewe, Cumbria, Doncaster, Dorset, East Berkshire, East Cheshire, East Devon, East of Scotland, East Suffolk, East Sussex, Gateshead, Gloucestershire, Great Yarmouth, Hereford and Worcester, Kent (Canterbury, Rochester, Maidstone), King's Lynn, Leicestershire, Liverpool, Manchester, Milton Keynes, Newcastle, North Birmingham, North East Scotland, North Lancashire, North Middlesex, North Nottingham, North of Scotland, North Tees, North Yorkshire, Nottingham, Oxford, Portsmouth, Rotherham, Sheffield, Shropshire, Somerset, South Birmingham, South East Scotland, South East Staffordshire, South Derbyshire, South Essex, South Lancashire, South West Scotland, Surrey, Warrington Halton St Helens and Knowsley, Warwickshire Solihull and Coventry, West Berkshire, West Devon, West London, West Suffolk, West Sussex, Wiltshire, Winchester, Wirral, and Wycombe.

  • Contributors: All authors participated in the design and conduct of the study and read and approved the final manuscript. GKR and VB are the guarantors.

  • Funding: The Million Women Study is supported by Cancer Research UK, the UK Medical Research Council, and the UK National Health Service breast screening programme. The funders did not influence the conduct of the study, the preparation of this report, or the decision to publish. The authors had full access to all the data in the study and had final responsibility for the decision to submit for publication.

  • Competing interests: None declared.

  • Ethical approval: Oxford and Anglia Multi-Centre Research and Ethics Committee.

    Provenance and peer review: Not commissioned; externally peer reviewed.

  • Accepted 5 October 2007
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