Author Contributions: Dr Reeves had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Reeves, Green, Beral, Bell, Lathrop, Peto.
Acquisition of data: Green, Tipper, Baker, Beral, Zelenika, Lathrop.
Analysis and interpretation of data: Reeves, Travis, Bull, Beral, Peto.
Drafting of the manuscript: Reeves, Travis, Bull, Tipper, Beral, Peto.
Critical revision of the manuscript for important intellectual content: Reeves, Travis, Green, Baker, Beral, Peto, Bell, Zelenika, Lathrop.
Statistical analysis: Reeves, Travis, Bull, Peto.
Obtained funding: Reeves, Green, Beral, Bell, Lathrop.
Administrative, technical, or material support: Tipper, Baker, Zelenika, Lathrop.
Study supervision: Beral.
Financial Disclosures: None reported.
Funding/Support: The Million Women Study is supported by the UK Medical Research Council and Cancer Research UK. Genotyping of blood samples was supported by the Institut National du Cancer, France.
Role of the Sponsors: The sponsors did not have any input into the study design or conduct; data collection, management, analysis, or interpretation; nor did they influence the preparation, review, or approval of the manuscript.
Million Women Study Steering Committee: Emily Banks, Valerie Beral, Ruth English, Jane Green, Julietta Patnick, Richard Peto, Gillian Reeves, Martin Vessey, Matthew Wallis.
NHS Breast Screening Centres collaborating in the Million Women Study (in alphabetical order): Avon, Aylesbury, Barnsley, Basingstoke, Bedfordshire & Hertfordshire, Cambridge & Huntingdon, Chelmsford & 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 & Worcester, Kent (Canterbury, Rochester, Maidstone), Kings 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 & Knowsley, Warwickshire Solihull & Coventry, West Berkshire, West Devon, West London, West Suffolk, West Sussex, Wiltshire, Winchester, Wirral, and Wycombe.
Million Women Study coordinating center staff: Simon Abbott, Naomi Allen, Miranda Armstrong, Krys Baker, Angela Balkwill, Vicky Benson, Valerie Beral, Judith Black, Anna Brown, Diana Bull, Benjamin Cairns, Andrew Chadwick, James Chivenga, Barbara Crossley, Francesca Crowe, Gabriela Czanner, Dave Ewart, Sarah Ewart, Lee Fletcher, Toral Gathani, Laura Gerrard, Adrian Goodill, Winifred Gray, Jane Green, Joy Hooley, Bryony Horner, Sau Wan Kan, Carol Keene, Nicky Langston, Isobel Lingard, Maria Jose Luque, Kath Moser, Lynn Pank, Kirstin Pirie, Gillian Reeves, Emma Sherman, Evie Shrerry-Starmer, Moya Simmonds, Helena Strange, Sian Sweetland, Owen Tang, Alison Timadjer, Sarah Tipper, Ruth Travis, Lyndsey Trickett, Joanna Watson, Steve Williams, Lucy Wright.
Additional Contributions: We thank the women who participated in the study, general practitioners who took blood samples, and staff from the NHS Breast Screening Centres. We also thank Adrian Goodill (Cancer Epidemiology Unit, Oxford University) for preparation of the figures. No compensation was received.