Objective There has been considerable interest in the impact of reproductive factors on health but there are little data on how these have varied over time. We explore trends in reproductive/lifestyle factors of postmenopausal British women by analysing self-reported data from participants of the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS).
Design Prospective birth cohort analysis.
Setting Population cohort invited between 2001 and 2005 from age-sex registers of 27 Primary Care Trusts in England, Wales and Northern Ireland and recruited through 13 National Health Service Trusts.
Participants 202 638 postmenopausal women aged 50–74 years at randomisation to UKCTOCS between April 2001 and October 2005.
Interventions Women were stratified into the following six birth cohorts (1925–1929, 1930–1934, 1935–1939, 1940–1944, 1945–1949, 1950–1955) based on year of birth. Self-reported data on reproductive factors provided at recruitment were explored using tabular and graphical summaries to examine for differences between the birth cohorts.
Outcome measures Trends in mean age at menarche and menopause, use of oral contraceptives, change in family size, infertility treatments, tubal ligation and hysterectomy rates.
Results Women born between 1935 and 1955 made up 86% of the cohort. Median age at menarche decreased from 13.4 for women born between 1925 and 1929 to 12.8 for women born between 1950 and 1955. Increased use of the oral contraceptives, infertility treatments and smaller family size was observed in the younger birth cohorts. Tubal ligation rates increased for those born between 1925 and 1945, but this increase did not persist in subsequent cohorts. Hysterectomy rates (17–20%) did not change over time.
Conclusions The trends seen in this large cohort are likely to reflect the reproductive history of the UK female postmenopausal population of similar age. Since these are risk factors for hormone-related cancers, these trends are important in understanding the changing incidence of these cancers.
Trial registration number International Standard Randomised Controlled Trial Number: 22488978.
- birth cohort
- postmenopausal women
- reproductive factors
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Contributors UM and AG-M were involved in the study design and drafted the manuscript. AG-M and CG did the literature search for this manuscript and prepared the tables. AG-M, CG and MB did the statistical analysis. AG-M, CG, MB and UM were involved in the interpretation of the data. UM, AG-M, CG, MB, AR, HB, JK, RW, SS, SC, MP and IJ critically revised the manuscript and approved the final version. UM is the guarantor.
Funding UKCTOCS was core funded by the Medical Research Council, Cancer Research UK, and the Department of Health with additional support from the Eve Appeal, Special Trustees of Bart's and the London, and Special Trustees of UCLH and supported by researchers at the National Institute for Health Research University College London Hospitals Biomedical Research Centre. The funding source or the sponsor had no role in the data collection, data analysis, data interpretation or writing of the report. The researchers are independent from the funders.
Competing interests UM and IJ have a financial interest through Abcodia in the third party exploitation of the trial biobank. IJ and SJS are Co-inventors of the ‘Risk of Ovarian Cancer Algorithm’, which has been licensed to Abcodia. The remaining authors declare no conflict of interest.
Patient consent Not obtained.
Ethics approval The study was approved by the UK North West Multicentre Research Ethics Committees (North West MREC 00/8/34) on 21 June 2000 with site-specific approval from the local regional ethics committees and the Caldicott guardians (data controllers) of the primary care trusts.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement No additional data are available.
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