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Centre for Evidence-
Based Medicine

Oral contraceptive pills has no lasting effect on mortality

Purchasing Bottom Line

The oral contraceptive pill does not seem to have lasting effects on mortality, particularly after 10 years' cessation.

Citation

Beral V, Hermon C, Kay C, Hannaford P, Darby S, Reeves G. Mortality associated with oral contraceptive use: 25 year follow up of cohort of 46,000 women from Royal College of General Practitioners' oral contraception study. BMJ 1999;318:96-100

Purchasing Question

What is the risk of death in women who are taking oral contraceptives?

Search Terms

MEDLINE search using mortality, oral contraception, exp cohort studies

The Study

25 year prospective cohort study, starting May 1968, of 46,000 women from 1400 General Practices throughout Britain (75% follow up due to GPs dropping out before routine flagging occurred, not due to systematic differences in women leaving the study). GPs provided routine information about prescribing oral contraceptives, pregnancies, new illness and deaths. Deaths were also recorded from the English and Scottish central registers and coded according to ICD-8, up to 31/12/93. Exposure was measured in person-years, and years from cessation were noted. The analysis controlled for social class, age, parity and smoking.

The Evidence

Adverse Outcome
(death from all causes*)
Totals
Present (case) Absent (case)
Exposed to the Treatment Yes (Cohort)

0.0018

a

0.9982

b

a + b

No (Cohort)

0.0019

c

0.9981

d

c + d

Totals

a + c

b + d

a + b + c + d

* note that you could use this table to analyse risks of death from specific causes using the data in Tables 4 & 5. These figures are taken from the "ever vs. never" used columns in table 1, with the person-year denominators (517,519 vs 335,998) in the ever vs never groups on page 97.
** note that the death rates uses person-years as the denominator, rather than people. That is, if you take the pill for one year, you can expect a death rate from all causes of 0.18% = 945 deaths/517,519 person years [page 97]
*** In this study, relative risk = RR = 0.0018/0.0019 = 0.95, and when adjusted for several baseline differences, RR to 1.1 (95% CI 0.9-1.1, p value of 0.7) i.e. there is no significant difference in death between the two groups.

Comments

In this study, relative risk = RR = 0.0018/0.0019 = 0.95, and when adjusted for several baseline differences, RR to 1.1 (95% CI 0.9-1.1, p value of 0.7) i.e. there is no significant difference in death between the two groups.

Appraised By

Anna Donald and Sam Vincent March 1999.

Expiry Date

March 2001