Recruitment and data collection
The study has ethical approval from the East of England-Cambridge South Research Ethics Committee (Ref 97/5/01). Ethics approval for the recruitment into the study was initially obtained region by region, in 1996, and as a multi-centre cohort study in 1997.
Women were sent the initial Million Women Study recruitment questionnaire with their invitation to attend the National Health Service Breast Screening Programme at 66 participating centres across England and Scotland, between 1996 and 2001. A total of 1.3 women were recruited to the study, which equates to about one in four of all women born between 1935 and 1950 in the UK. The study pioneered the use of optical recognition software to easily capture the data contained in such a large number of paper questionnaires.
Approximately three years after completing the first questionnaire, participants were sent a re-survey questionnaire to keep track of their health and to ask new questions about factors such as diet, family history, and early life experiences. Re-survey questionnaires have since been sent to all surviving women in the study at approximately three to five yearly intervals. Some women have also been sent additional postal or online questionnaires.
Some 50,000 women in the cohort have also provided blood or saliva samples through the related Disease Susceptibility in Women Study. A small number of participants have been interviewed about their lifestyles in retirement for a related study called Changes to Lifestyle in Retirement.
Our research would not be possible without having both the information from the questionnaires and the linked follow-up information on health which we receive from NHS health records. This provides us with a virtually complete record of relevant health outcomes for all of the women in the study. We currently have electronic linkage of the entire cohort to NHS databases for deaths, emigrations, cancer registrations and hospital admissions.
For our research on dementia we currently rely on the information provided in the hospital admission records. As not everyone with dementia is admitted to hospital, we would now like to improve the completeness of our diagnostic record and following consultation with our participant panel, we are applying to the NHS data providers to add another routinely-collected NHS dataset to the study: the Mental Health Services Dataset. In England, the Mental Health Services Dataset collects information from outpatient and community clinics, including memory clinics. We might also use the Mental Health Services Dataset to help identify women with other mental health diagnoses, which may not be included in hospital records.