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Establishing a Competing Risk Regression Nomogram Model for Survival Data
Published on: October 23, 2020
Factors affecting mortality in a large cohort study with special reference to oral contraceptive use
Martin Vessey1, David Yeates, Susan Flynn
1Unit of Health Care Epidemiology, University of Oxford, Oxford, UK. martin.vessey@dphpc.ox.ac.uk
Background:
This analysis updates mortality in the Oxford-Family Planning Association (Oxford-FPA) contraceptive study, with emphasis on oral contraceptive (OC) use.
Study Design:
The Oxford-FPA study includes 17,032 women recruited from 1968-1974 at contraceptive clinics, aged 25-39 years, using OCs a diaphragm or an intrauterine device. Follow-up has been to March 2009; by then, 1715 women had died.
Results:
The rate ratio (RR) for overall mortality was 0.87 (CI 0.79-0.96), comparing ever-users of OCs with never-users. The RR for fatal cervical cancer was increased (7.3), but the CIs were very wide (1.2-305). There was no association between ever-use of OCs and mortality from breast cancer (RR 1.0, CI 0.8-1.2), nor was fatal breast cancer related to duration of OC use. OC use strongly protected against death from other uterine cancer and ovarian cancer; RRs for ever-use of OCs were 0.3 (CI 0.1-0.8) and 0.4 (CI 0.3-0.6), respectively. Protection increased with duration of OC use and persisted more than 20 years after cessation. Circulatory disease mortality was not increased, the RR for ever-use of OCs being 0.9 (CI 0.7-1.1). The overall mortality RR for all women smoking 15+ cigarettes daily was 2.25 (CI 1.99-2.53) and, for all women with a body mass index of 28+ kg/m(2), was 1.33 (CI 1.07-1.64).
Conclusions:
Long-term follow-up strongly suggests that OC use slightly reduces all cause mortality.
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