The Million Women Study

This is a Longitudinal Population Studies application for core infrastructure support for the Million Women Study (MWS). The study started in 1996 and includes 1.3 million UK women born between 1935 and 1950. It is the largest study of women’s health in the world. Its primary aim was to assess whether the risk of breast cancer is affected by menopausal hormone therapy use, but it was also designed to answer a much wider range of research questions about women’s health as they age. Since recruitment, cohort participants have been re-surveyed at regular intervals and followed for health outcomes through NHS databases. The MWS has already helped clarify the role of important modifiable risk factors for many diseases and these findings have informed clinical practice and public health guidance, particularly around use of menopausal hormone therapy. With continued support for cohort maintenance and enhancement, and improved data access, the study will be well placed to provide reliable information on many other outstanding questions including those relating to the aetiology of cardiovascular disease in women, determinants of healthy ageing, and the role of environmental pollution in disease incidence. The MWS has collected a wealth of longitudinal data on participants including information on socio-demographic, lifestyle and health factors, as well as biomarker and genetic data. It has also been linked to a wide range of NHS databases for ascertainment of disease outcomes. The development of robust processes for maintaining the existing database and incorporation of increasingly complex data from additional sources, including disease biomarkers and clinical data, is essential to ensure high-quality research. This requires a team of specialists and researchers with relevant experience in the management of large population-based studies and use of electronic healthcare data. Since 2019, the study’s new chief investigator has been actively seeking to widen access to the study’s rich database and in July 2024, successfully secured an international sublicence for onward sharing of linked MWS and NHS health outcome data. This will transform the way study data is shared with other researchers. We will implement a framework for data access, which will involve onboarding the MWS to the national Trusted Research Environment for longitudinal research, the UK Longitudinal Linkage Collaboration (LLC), which is hosted on the Secure eResearch Platform (SeRP) provided by Swansea University. LLC provides strong confidentiality safeguards, efficient NHS database follow-up, and opportunities for joint analysis with other studies. In partnership with LLC, we will also link the entire cohort to national environmental data and to the Medicines Dispensed in Primary Care dataset, opening the study to researchers in environmental and pharmacological epidemiology. Since LLC can only currently share data with UK researchers, the proposed framework includes provision of a minimal remote access platform on SeRP where we can deposit bespoke linked datasets to facilitate secure data access to researchers outside the UK. Given that 40% of recent applications have been from researchers outside the UK, this platform will address a clear scientific need. A further key aspect of the planned work is the development of a long-term plan for active engagement with participants including expansion of the participant panel membership. We will also raise the profile of the study and improve the discoverability and impact of the resource through targeted communications with researchers and other stakeholders.