| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Special Articles |
Cancer and Public Health Department of Epidemiology and Population Health London School of Hygiene and Tropical Medicine London WC1E 7HT, United Kingdom
 |
Introduction |
|---|
 Top Introduction References |
|---|
What has happened since that time has served to consolidate that general picture. First, basic laboratory science has confirmed a plausible mechanism and the size of the estimated effect (1). Third-generation pills may exert an extra thrombogenic effect by inducing a resistance to activated protein C in the blood. In epidemiology it is quite rare to have several studies all pointing in the same direction; and then, for a plausible mechanism for such findings to be confirmed in the laboratory is especially unusual. For all this to happen so quickly is rarer still.
Second, attempts to invoke selection or prescribing bias for the results of the various studies have, in my view, failed (2)—in spite of intensive effort among those with fiscal interests in sales and others. However, it is not clear that this is widely believed, for it is nonetheless easy to instill doubt successfully, even without strong evidence. In this case evidence for bias, by its very nature, will rarely be strong, unless one particularly wants to believe it. Most modern observational epidemiology tries hard to avoid obvious bias, simply because it will always be open to criticism from skeptics. However the identification of residual bias in all these studies, which comes close to explaining the results, will never be conclusive.
But we live in a world where risk is assessed, and the evidence sought and promulgated (3), in an essentially irrational manner. This extra risk for VTE’s, for which the baseline risk is low, has been the subject of rather more heat than light—certainly in the United Kingdom. A recent editorial in the BMJ (4) infers that we have a special problem with "pill scares," and that may be right. I happen to think that we all have a long way to go before the notion of risk can be put in any kind of real perspective, because strong vested interests exist and because people live in varying circumstances where real opportunities for choice are effectively constrained in very different ways. These matters are complicated, and glib assessments will never be enough. What is clear is that the baseline risk of VTE is low but the particular increase attributable to third-generation OC’s is real.
The essential issues surrounding this question in practice are concerned with four dominant areas for individual women. These are: reliable and acceptable contraception, venous thromboembolism risk, myocardial infarction (MI) risk, and important interactions with other important aspects of life. Different OC’s feel different to different women, and that is important while reliable and acceptable contraception is important to them. Breast tenderness is tedious, as are varying degrees of libido loss. Some of this may be supplier-induced, but most might be real; either way they are important. Thus if second-generation pills give rise to unwanted side effects that are attenuated, for some women, by the new progestins then, for such women, that is important. But it is no good saying that the increased risk of VTE does not matter at all. It is bound to matter a little to some, and possibly a lot to others. We all take risks, and we all have to learn how to put them into a sensible perspective (5).
VTE’s are clearly worth avoiding but are rare for most women, as are MI’s, which are not so rare. Women who smoke seriously increase their risk of MI (6) on both new and old type OC’s. This is quite a serious risk, and young women seem to smoke increasingly commonly. Probably third-generation OC’s will bestow a lower overall MI risk profile, but that has to be weighed against the higher VTE risk, which is as good as certain. This putative beneficial effect on MI of third-generation OC’s unfortunately is not (7). Compared with the (possibly synergistic) effect of increasing MI risk in other ways (like smoking, little exercise, and diet), these decisions for women are marginal and over-emphasised. However marginal, women do need to know of their existence.
The irrational part of all this is that tobacco companies continue to market, advertise, and sell their lethal product in every corner shop in the world. Every restriction simply moves the effort to places where rational resistance is more difficult, for various reasons. Cigarettes double the risk of premature death for those who consume them as indicated. They multiply the risk of immediate MI among pill users by around ten (8). Cigarettes are addictive to young girls, as they are to everyone, and millions of us make money from the easy profits accumulated from selling such things to young (and consequently to older) people. To even mention an increased risk of VTE’s for a product that has so much going for it otherwise is nearly irrelevant in that context. Young women won’t die for using the wrong kind of contraceptive on the whole, nor will they die from smoking, but they may die from the addictive consequences if they smoke after age 35 (9).
Smoking and using OC’s is definitely a bad idea, because the effect is synergistic. Smoking may be a necessary part of growing up for many girls, and for many girls having safe sex is what growing up is largely about, but by the time safe sex is important, many are already hooked on tobacco. To tell these women, and often terrify them, about venous thromboembolism seems just crazy, in the context. Tell them about myocardial infarction whose risk is greatly multiplied due to smoking. In the United Kingdom, the Committee on the Safety of Medicines told women in 1995 about VTE’s and third-generation OC’s, and apparently 30,000 unwanted pregnancies resulted (10).
It would be much better to think of some way of disabling the tobacco giants from continuing to corrupt rational discussion of risk by resisting any attempt to curb their evil profiteering and ritually sowing confusion on personal choice and addictive behaviour. Pill companies have to demonstrate safety for a product with manifest and dramatic advantages. Quitting the pill for a short while, to avoid real or perceived risk, has very different consequences from quitting tobacco for a short while. But better to get on with life while avoiding the serious immediate risks, like HIV and DVT, and the long-term ones like MI and lung cancer. In the end, as far as we now know, OC’s of any kind do not importantly affect a woman’s long-term chance of serious illness overall, and that is very important news. Not so for cigarettes, which prevent neither unwanted pregnancies nor HIV.
|
References |
|---|
|
TopIntroductionReferences |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
