The Million Women Study is a prospective cohort study of 1.3 million women in the UK, established in 1996.

The Million Women Study is one of the largest studies of women’s health in the world, funded mainly by Cancer Research UK and the Medical Research Council. Over 1.3 million women in the UK were recruited between 1996 and 2001, in collaboration with the UK National Health Service (NHS) Breast Screening Programme, and their health is being followed through linkage to NHS medical records and through follow-up questionnaires.  The study’s main original aim was to investigate the effect of hormone replacement therapy (HRT) on risk of breast and other cancers;  but the large size of the study means that a very broad range of health issues can be addressed, and as well as cancer, we are now investigating heart disease, stroke, blood clots, osteoporosis and fractures, and neurodegenerative disease, including dementia. The focus remains on providing reliable evidence on potentially modifiable risk factors for serious and common diseases in women, as a contribution to public health.

Major publications include the first paper on breast cancer and HRT in the Million Women Study, published in August 2003 (Million Women Study Collaborators, 2003), and subsequent reports on fractures (2003 onwards ), breast screening (2004), endometrial cancer (2005), ovarian cancer (2007), on cancer risk associated with obesity (2007) moderate alcohol intake (2009), height (2011) and birth weight (2014); and recent papers on the long-term effects of smoking in women (2013) and on hospital admissions related to overweight and obesity (2014)

Full details of the Million Women Study, including links to these and other publications, are available on the website

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