Study Confirms Oral Contraceptive Use is Not Harmful, But Smoking Is

About the Study

The researchers recruited 17,032 women from 17 family planning clinics in England and Scotland between January 1, 1968 and December 31, 1974. To be eligible, women had to be aged 25-39 years, married, white, British, and have been a user of either the contraceptive pill (which, for two-thirds of the women, contained 50 micrograms (µg) of estrogen) for at least five months, or a diaphragm or intrauterine device for at least five months without previous pill use.

Participants were asked about their child-bearing history, smoking habits, and medical history at recruitment. During yearly follow-up clinic visits until they were 45 years of age, participants were asked about pregnancies, changes in contraceptive practices, hospital visits, menopause status, and hormone replacement therapy (HRT) use.

At age 45, the participants were assigned to one of three groups on the basis of OC use: never used, used for eight years or more, or used for less than eight years. The researchers continued to annually follow-up with women in the first two groups, until mid-1994. After that point, they assessed mortality only (through December 31, 2000).

The Findings

The researchers analyzed the 889 deaths that occurred in the study group. They found no evidence of a harmful effect of OC use on mortality from breast, lung, colorectal, lymphatic, or skin cancer. Risk of death from cervical cancer was slightly increased—but not significantly—in OC users. Mortality from ovarian cancer was significantly reduced in women who had used OCs for more than four years.

In a separate analysis, lung (but no other) cancer was significantly associated with heavy smoking (defined as 15 or more cigarettes per day).

Heavy smoking, but not OC use, significantly increased risk of mortality from ischemic heart disease and hemorrhagic stroke. For women who used OCs and smoked heavily, the risk of death from ischemic heart disease was about two times that of non-smoking OC users (the association was significant only for those women who used OCs for 49-96 months).

Finally, the researchers looked at mortality rates from all causes and found there was no significant difference between the risk of death among ever-users of OC compared to never-users. In contrast, compared to non-smokers, risk of mortality from all causes was increased by 24% for light smokers (who smoked fewer than 15 cigarettes per day) and by more than 100% among heavy smokers.

The mortality rates, however, may be misleading since the study did not take into account the medical care received by subjects with serious illnesses (such as ischemic heart disease). In addition, since the analysis only considered how much the women smoked at the onset of the study, the results may under or overestimate the effect of smoking.

How Does This Affect You?

This study adds strength to the view that oral contraceptives used in the 1970s and ‘80s have no adverse effect on overall mortality. Although the results do not necessarily apply to the pills used today, it is reasonable to assume that contemporary OCs, with their extremely low-dose of hormones, are even safer. And, while there is some suggestion that long-term use of OCs may slightly increase the risk of cervical cancer, changes in the cervix can readily be detected with regular Pap smear screening well before they cause harm.

On the other hand, women who smoke—particularly those who smoke heavily—have a choice to make: cigarettes or oral contraceptives. If they are unprepared to ]]>quit smoking]]> , it is probably best to avoid OCs. Not only is their risk of dying from any cause much higher than for nonsmokers, using OCs adds an additional risk of early death from cardiovascular disease.

The bottom line: If you are looking for a safe and effective form of birth control, OCs appear to be a great option. If you smoke and cannot quit, choose a different method, especially if you’re over 35.