Further insight gained on impact of OC use
April 1, 1999
Further insight gained on impact of OC use
A cohort study of 46,000 British women, half of whom were using oral contraceptives (OCs), gives family planners further insight into the long-term effects of pill use.1 The study shows that OCs seem to have their main effect on mortality while they are being used and in the 10 years after stopping use.
Ten or more years after stopping use, mortality rates were similar in past users and never-users. There is little evidence to suggest any persistent adverse effect 10 or more years after women stop OC use, researchers conclude.
Robert Hatcher, MD, MPH, professor of OB/GYN at Emory University in Atlanta and lead author of Contraceptive Technology, terms the findings "good news."
"The study showed that there were no causes of death that were increased in women who quit pills more than 10 years ago, which is great," he notes.
Implications of the study
Although this study provides confidence that long-term OC use does not increase mortality, further investigation is needed in regard to pill use and cause-specific mortality, notes Andrew Kaunitz, MD, professor and assistant chair of the department of obstetrics and gynecology at the University of Florida Health Sciences Center in Jacksonville.
The study is a 25-year follow up of women enrolled in the Manchester, England-based Royal College of General Practitioners’ OC study. Set up in 1968 to monitor the health of OC users, the study recruited 23,000 women who were using the Pill and a similar number of never-users. General practitioners were asked to provide information on the type of OC prescribed, pregnancies, new illness, or death for each woman every six months. Most of the women who used the Pill used combined OCs with 50 mcg estrogen.
By December 1993, the cohort had been followed for 25 years, and the median age of the women was 49. During that period, 1,599 deaths were reported, with 945 deaths occurring in those women who had ever used OCs and 654 in never-users. Over the entire period, the risk of death from all causes was similar in women who had used the Pill and those who never had, and the risk of death for most specific causes did not differ significantly between the two groups.
Looking at risks
Among current users and recent users (those who had used within 10 years), the relative risk of death from ovarian cancer was 0.2; from cervical cancer, 2.5; and from cerebrovascular disease, 1.9. For women who had stopped using the Pill 10 or more years previously, there were no significant excesses or deficits either overall or for any specific cause of death, the researchers report.
"My concern with this study it does not have the statistical power to analyze cause-specific mortality," notes Kaunitz. "For instance, there were not enough cases of fatal ovarian or cervical cancer to draw meaningful inferences [regarding] the impact of OC use on fatalities from these two malignancies."
When family planners look to determine the impact of OCs on certain conditions such as malignancies, epidemiologic case-control studies that include large numbers of incident cases of a given malignancy offer a better understanding, Kaunitz suggests.
Hatcher points to a comprehensive review and re-analysis of 54 studies that represent 90% of the world’s data on the subject. The re-analysis showed current OC users at a 24% increased risk for having breast cancer diagnosed. One to four years after discontinuing pills, the risk falls to 16%, and after five to nine years, the risk drops to 7%. More than 10 years out from stopping pill use, women are at no significantly increased risk. (For further information on the study, see Contraceptive Technology Update, December 1996, p. 147.)
Use this analogy developed by British family planner John Guillebaud, MA, FRCSE, FRCOG, MFFP, director of the Margaret Pyke Family Planning Centre in London, to explain risks to women, Hatcher suggests:
Imagine two halls, each holding 1,000 women who are age 45. In one hall, none of the women has ever used the Pill. In the other hall, all the women used the pill until age 35, 10 years ago. What would be the risks for breast cancer among the women in the two halls?
In the hall with never-users of OCs, 10 women would be diagnosed with breast cancer. In the other hall, 11 women — just one more — would be diagnosed with the disease. Moreover, the remaining 989 past pill-using women have the same risk for the disease from now on as those who never used the Pill.
"This is reassuring to millions of women who took the pill in the past," write Hatcher and Guillebaud in Contraceptive Technology.3 "In addition, the cancers diagnosed in women who use or who have ever used OCs are less advanced than those who have never used the pill and are less likely to have spread beyond the breast."
References
1. Beral V, Hermon C, Kay C, et al. 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.
2. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: Collab orative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996; 347:1713-1727.
3. Hatcher RA, Trussell J, Stewart F, et al. Contraceptive Technology. 17th ed. New York, NY: Ardent Media; 1998.
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