The long-running saga of health claims about the pill.

Health and medicine explained.
Jan. 29 2008 4:59 PM

The Pill, a Rock Opera

Its long-running health saga.

Birth control pills
The pill

Last week, British researchers published decisively good news about birth control pills: They lower the risk of ovarian cancer—substantially. The longer women take the pill, the lower their odds of getting this kind of cancer. And some of the benefits seem to persist, even decades after women go off the contraception. The new analysis pooled large amounts of data. It was elegantly done. And it's worth celebrating, partly because health claims about the pill are often much harder to parse.

Consider the mental tightrope we've been asked to walk when it comes to the effect of oral contraception on sex drive, cardiovascular disease, and breast cancer: The pill may sap our libidos (say Scottish doctors)—but it may also be linked to more frequent orgasms (say Italian ones). It increases the risk of blood clots, and may slightly increase the risk of strokes (which remains very small). But it doesn't seem to up the odds of a heart attack, at least for nonsmokers, and might even offer some cardio protection. At the same time, in contrast to the new findings that it protects against ovarian cancer, the pill may slightly increase the risk of breast cancer. And, then again, it may not, especially when newer formulations with lower doses of estrogen are considered. In other words, oral contraception is a moving target for medical research, and its health history would make for a first-rate feminist rock opera. The grand finale? The pill gets better with age.

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When Margaret Sanger first dreamed of a "magic pill" to prevent unwanted pregnancy, and then its actual appearance came to symbolize sexual and personal freedom for women, few wanted to dwell on tough questions about potential health hazards. But in 1969, journalist Barbara Seaman forced the issue with her book The Doctor's Case Against the Pill. Congressional hearings followed, helping to galvanize a feminist backlash against the pill, and against doctors and medical paternalism in general (see: the 1970s). Today, though more than 100 million women around the world use oral contraception, suspicion lingers about possible risks like cancer and strokes. And pro-lifers gleefully fan the flames, claiming against all reason and medical evidence that the pill causes early abortions. All of which is to say that whether new findings about the pill weigh in for health benefits or for risks, they are always freighted.

Take one evergreen headline: "Does the Pill Make Women Frigid?" In 1995, Scottish researchers found that women taking pills with estrogen and progestin in them reported decreased interest in sex (though women taking progestin-only pills did not). More recently, the idea that women's sex drive is linked to testosterone levels has gained ground. (That's the theory behind the testosterone skin patch, one candidate for Lady Viagra.) Some forms of the pill seem to indirectly reduce women's blood levels of testosterone—and that decline may persist even after they stop taking the pill, one study suggests.

But the testosterone story has caveats. Women's sex drive clearly depends on a host of factors, many of them psychological. Surely, the freedom of sex without fear of pregnancy can be a turn-on. And recently, Italian researchers found that women who took birth control pills containing 30 micrograms of estrogen and 3 milligrams of a progestin called drospirenone reported greater sexual enjoyment and greater frequency of orgasm than they did before. Sounds almost like Lady Viagra.

Claims about the pill and cardiovascular disease also go both ways. In 1961, the Lancet reported that a nurse using oral contraception had suffered a pulmonary embolism—the first such report to appear in the literature, according to this 2005 review. In the years that followed, several epidemiological studies found that the pill upped the odds of blood clots, pulmonary embolisms, strokes, and heart attacks (although the risks of these problems remained small). In 1988, for instance, data from the large and prospective Nurses Health Study showed that women taking oral contraception were two and a half times as likely to have heart attacks as women who were not.

More recently, however, research has tried to tease out the impact of the pill on women who smoke, or have diabetes or hypertension, from its effect on women who don't. The Nurses Health Study concluded that for nonsmokers, the pill does not increase the risk of heart disease. Other studies back this up, as well. And in 2006, researchers at Cedars-Sinai Research Institute in Los Angeles found that past use of oral contraception may actually lower women's risk of heart problems. (Still, wild cards like this unpublished study, which turned up higher rates of atherosclerosis in women taking the pill for extended periods of time, keep everyone on edge.)

And then there is breast cancer. In the mid-1990s, a large meta-analysis linked birth control pills to a small increase in women's odds of getting breast cancer. The increased risk began to decrease again when they stopped taking the pill, but took 10 years to disappear entirely. By contrast, in 2002, another major study published in the New England Journal of Medicine found that use of the pill was not associated with breast cancer risk, even for women who took it for longer periods of time or used formulations with higher doses of estrogen. Since then, more dueling findings have appeared. In the end, the bottom line tends toward reassurance. Recent evidence suggests that newer pills pose less of a risk than older ones. And a helpful summary published this month argues that when all is said and done, today's birth control pills "do not play a clinically important role in the risk of breast cancer." (See here for a rundown of other health claims about the pill, good and bad.)

Meanwhile, the news on ovarian cancer has long been consistently good. Friday's findings, published in the Lancet, seal the deal. Researchers pooled data from 45 epidemiological studies, including more than 23,000 women with ovarian cancer and more than 87,000 controls. They found that for every five years on the pill, women's relative risk of ovarian cancer was reduced by 20 percent. After 15 years on the pill, the risk was cut in half. The pill probably protects against this kind of cancer because it suppresses ovulation, in which the ovary releases an egg. The group estimates that 200,000 cases of ovarian cancer and 100,000 deaths from the disease have been prevented to date by oral contraception.

Whatever else we don't know about the magic pill, here's to that.

Amanda Schaffer is a science and medical columnist for Slate.

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