Factors affecting mortality in a large cohort study with special reference to oral contraceptive use.
BACKGROUND
This analysis updates mortality in the Oxford-Family Planning Association (Oxford-FPA) contraceptive study, with emphasis on oral contraceptive (OC) use.


METHODS
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.
Vessey
Martin
M
Unit of Health Care Epidemiology, University of Oxford, Oxford, UK. martin.vessey@dphpc.ox.ac.uk
Yeates
David
D
Flynn
Susan
S
D000328:Adult; D015331:Cohort Studies; D003267:Contraception / Q000379:methods*; D003278:Contraceptives, Oral, Hormonal / Q000008:administration & dosage*; D005260:Female; D005833:Genital Neoplasms, Female / Q000401:mortality; D006801:Humans; D009026:Mortality; D011795:Surveys and Questionnaires
D003278:Contraceptives, Oral, Hormonal