Mortality among contraceptive pill users: cohort evidence from Royal College of General Practitioners’ Oral Contraception Study
BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c927 (Published 12 March 2010) Cite this as: BMJ 2010;340:c927
- Philip C Hannaford, Grampian Health Board chair of primary care1,
- Lisa Iversen, research fellow1,
- Tatiana V Macfarlane, senior research fellow2,
- Alison M Elliott, senior research fellow1,
- Valerie Angus, data manager3,
- Amanda J Lee, professor of medical statistics4
- 1Centre of Academic Primary Care, University of Aberdeen, Foresterhill Health Centre, Aberdeen AB25 2AY
- 2Division of Applied Medicine, University of Aberdeen, School of Medicine and Dentistry, Foresterhill, Aberdeen AB25 2ZD
- 3College of Life Sciences and Medicine, Foresterhill, Aberdeen AB25 2ZD
- 4Medical Statistics Team, Section of Population Health, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD
- Correspondence to: P Hannaford p.hannaford{at}abdn.ac.uk
- Accepted 5 January 2010
Abstract
Objective To see if the mortality risk among women who have used oral contraceptives differs from that of never users.
Design Prospective cohort study started in 1968 with mortality data supplied by participating general practitioners, National Health Service central registries, or both.
Setting 1400 general practices throughout the United Kingdom.
Participants 46 112 women observed for up to 39 years, resulting in 378 006 woman years of observation among never users of oral contraception and 819 175 among ever users.
Main outcome measures Directly standardised adjusted relative risks between never and ever users for all cause and cause specific mortality.
Results 1747 deaths occurred in never users of oral contraception and 2864 in ever users. Compared with never users, ever users of oral contraception had a significantly lower rate of death from any cause (adjusted relative risk 0.88, 95% confidence interval 0.82 to 0.93). They also had significantly lower rates of death from all cancers; large bowel/rectum, uterine body, and ovarian cancer; main gynaecological cancers combined; all circulatory disease; ischaemic heart disease; and all other diseases. They had higher rates of violent deaths. No association between overall mortality and duration of oral contraceptive use was observed, although some disease specific relations were apparent. An increased relative risk of death from any cause between ever users and never users was observed in women aged under 45 years who had stopped using oral contraceptives 5-9 years previously but not in those with more distant use. The estimated absolute reduction in all cause mortality among ever users of oral contraception was 52 per 100 000 woman years.
Conclusion Oral contraception was not associated with an increased long term risk of death in this large UK cohort; indeed, a net benefit was apparent. The balance of risks and benefits, however, may vary globally, depending on patterns of oral contraception usage and background risk of disease.
Footnotes
This paper would not have been possible without the leadership of Clifford Kay, who established and ran the study for its first 26 years, or the many general practitioners who contributed data. We also thank Aileen Murphy for database administration support and Sivasubramaniam Selvaraj who wrote most of the programming in Stata.
Contributors: PCH had the original idea, advised on and checked the analyses, and wrote the first and subsequent drafts of the paper. LI and AME had responsibility for updating the database with information on deaths. LI and VA checked the data extractions and analyses. TM was responsible for data analysis. AJL, with AME, checked the validity of the program used to analyse the data. VA maintained the study database and extracted data for analysis. All authors contributed to the scientific development of the paper, commented on successive drafts, and agreed to the final manuscript. PCH is the guarantor.
Funding: The study received funding from the Royal College of General Practitioners, Medical Research Council, Imperial Cancer Research Fund, British Heart Foundation, Cruden Foundation, Schering AG, Schering Health Care, Wyeth Ayerst International, Ortho Cilag, and Searle. None of the funders had a role in the data collection, analysis, or interpretation or in the writing of this paper.
Competing interests: The Centre of Academic Primary Care has received payments from Schering Plough and Wyeth Pharmaceutical for lectures and advisory board work provided by PCH.
Ethical approval: The study was established before the introduction of research ethics committees in the UK. Even so, procedures were used to maintain the confidentiality of women. Correspondence between participating doctors and the study, and between the NHS central registries and the study, used a unique study number, the key to which only the general practitioners knew.
Data sharing: No additional data available.
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