Communicating risk is one of the biggest challenges health professionals (and health journalists) face.
Take the news that 23 women died while taking the popular birth control pills Yaz and Yasmin. It is certainly disturbing. Still, it is important to ask questions to understand that number better: 23 out of how many? Over what time period? Yes, these women were taking birth control pills when they died, but did they have other risk factors?
In other words, context is all-important.
We should never forget that all drugs have side effects. If they do not, they probably have no benefit either.
You have to balance risk and benefit.
So, let's look at oral contraceptives – birth control pills. They have a clear benefit: preventing pregnancy. You cannot overstate this: The Pill was one of the great medical and social advances of the 20th century because it gave women reproductive choice.
That choice, that control, is paramount to this day. That is why more than 40 per cent of Canadian women of reproductive age use oral contraceptives.
Birth control pills have secondary benefits too, such a regulating menstrual periods, reducing acne and even preventing some forms of cancer (notably ovarian).
The flip side is side effects. The principal one is venous thromboembolism, blood clots that usually form in the legs and can travel to the lungs and cause death. The evidence is inconclusive in the debate about whether The Pill increases the risk of breast cancer.
So let's focus on blood clots. Five to 10 of every 10,000 women will suffer a blood clot in any given year if they are not taking birth control. Taking The Pill increases that risk three to six times, depending on the formulation. But the risk is still low, 20 to 60 per 10,000. The risk of developing a blood clot while pregnant is about 60 per 10,000, generally higher than from using oral contraceptives. (Of course, pregnancy has benefits too.)
The risk of blood clots increases across the board for women who smoke, are overweight and are inactive. It also increases with age, which is why The Pill is not recommended for women who smoke and are over 35.
We can quibble about the precise numbers ad infinitum – and scientists do – but these are estimates based on the medical literature.
To put the numbers in more concrete terms, there are roughly 10 deaths and 1,200 non-fatal blood clots in women who take oral contraceptives each year. (This is based on an analysis from France where, like Canada, use of The Pill is common.)
But here is more important context: About 4,000 Canadians a year die from misuse of painkillers (including ordinary drugs like Aspirin). About 40 a year die from Tylenol – four times as many deaths as oral contraceptives.
Most birth control pills contain a combination of synthetic estrogen (estradiol) and progestogen (progestin). That has not changed since they came to market in the late 1950s. Neither have the risks: The first case of a blood clot was reported in a medical journal in 1961. What has changed is the dosage and the type of progestin used.
Yaz and Yasmin contain drospirenone, a form of progestin that seems to pose a greater risk of blood clots. But, again, you have to be careful. Yaz and Yasmin are popular with teens, first-time users of hormonal birth control. The risk of all drugs is always highest the first time they are taken, the so-called new user effect.
Why don't doctors just prescribe the more tried-and-true second-generation pills?
All birth control pills have essentially the same effectiveness for preventing pregnancy. Drug companies fiddle with the progestin seeking better secondary benefits and more market share.
Young women like Yaz and Yasmin because of its anti-androgen properties: the perception that it prevents acne and growth of facial hair. This is made clear – none too subtly – in ads.
Biologically, these oral contraceptives are similar to Diane-35, an acne medication commonly prescribed off-label as birth control. (There have been 11 deaths linked to Diane-35, something that has not been mentioned in the recent coverage of Yaz and Yasmin.)
France has banned Yaz, Yasmin and Diane-35 because health authorities there have deemed the risks outweigh the benefits. Removing the products from the market does not deprive women of access to oral contraceptives because there are many other brands with better safety profiles.
Health Canada takes a more hands-off approach. It argues that the risk of blood clots (and other side effects) with oral contraceptives are low and well-known.
But that's the real question: Are women adequately informed of the benefits and risks – and specifically of the relative risks of various brands – by product inserts and health professionals?
Or should they depend on the news media to alert and inform them?
Editor's Note: An earlier version of this story incorrectly said oral contraceptives are not recommended for women over 35. In fact, the pill is not recommended for women over 35 who smoke, but they are considered safe for other women that age.