Birth Control – Clarifying the (Small) Heart Attack & Stroke Risks

In a detailed analysis of a large national health database including over a million women ages 15-49, Danish researchers have clarified how various hormonal contraceptives might affect the risk for heart attack and stroke.

While these events are exceedingly rare in the young population of women using pills, the age at which women use hormonal contraception has crept up. Some women are using pills well into their 40’s and even up till menopause.  So it’s appropriate to take a gander at these vascular risks a bit more closely to ask just how much risk women are taking by using hormonal contraception.

And the answer is – not very much.

Let’s see if I can break it down for you –

The risk of heart attack and stroke is largely age-related, whether you take hormonal contraception or not. Women in their late 40’s having a risk of 6 per 10,000 compared with less than 1 per 10,000  for women under age 25.

Having diabetes, hypertension, hyperlipidemia, arrhythmias and being a smoker elevate the risk of heart attack and stroke. By about a factor of two in women up to age 49. Remember though, that the risks related to these factors will increase with age, so don’t let this low number make you too comfortable.

Taking estrogen containing birth control increases the risks of heart attack and stroke, but those risks are very, very small. Just how small?  If you are age 20 years old and are on the pill with no additional risk factors, your overall risk of a heart attack or stroke is about 100 times less than 1%.  If you are 45 and on the pill, your risk is increased from about 6 per 10,000 to 12 per 10,000, a risk that is about 10 times less than 1%.

The risk of stroke and heart attack from estrogen-containing hormonal birth control goes away when you stop taking it. That’s good, since the age at which women stop needing birth control is around the time heart disease risks start to rise.

The risks for heart attack and stroke are estrogen-dose related. This means that the higher the estrogen exposure, the higher the risks.

Here is a very simplistic rendering of how the vascular risks compared between methods. This rendering may not be entirely correct statistically, but I have to place the data into clinical context, and this works for me –

Vascular risks of Hormonal Contraception

Patch, Ring & 50 ug pills > 30 ug pills ≥ 20 ug pills > POPs > Mirena & Implanon

(POPs = progestin-only pills. ug = amount of ethinyl estradiol)

Overall, the difference in risk between the highest and lowest risk hormonal methods is still quite small. Within a given estrogen dose class, the differences between brands of pills is negligible. In some cases, the risk of a 30 ug pill may be the same or lower than some 20 ug pills.

Noticeably absent from the analysis were the 20 ug norethindrone and levonogestrel pills, my personal go to pills for new pill starts these days.

There is also a new pill being marketed that contains just 10 ug of estrogen. If you’re willing to put up with a bit of breakthrough bleeding and want what this study suggests will be a lower risk of vascular side effects, that pill is sure to be a good choice for you.  I personally like it in the over 40 crowd.

Finally, it’s worth noting how good Yaz looks in this study – it’s a 20 ug pill, and no heart attacks were noted among Yaz users in this study. Their numbers were small relative to other pills, however, and the researchers caution that differences between different formulations of pills of the same estrogen dose were not statistically significant.

Bottom Line

Nothing in life is risk free, and that includes birth control. The good news is that the risks are low, and we now have data that women and their doctors can use in deciding between methods based on vascular risks. Or, as Diana Pettiti, MD, MPH states in her excellent editorial accompanying the article

Women, their physicians, and the public should be reassured not only by the Danish study but by the vast body of evidence from epidemiologic studies of hormonal contraception that have been done over the past five decades. This body of research documents the small magnitude of the problem of arterial thrombotic events in women using combined estrogen–progestin hormonal contraceptives. The research shows that the small risk could be minimized and perhaps eliminated by abstinence from smoking and by checking blood pressure, with avoidance of hormonal contraceptive use if blood pressure is raised.12 With the addition of the Danish data, evidence is now even stronger that progestin-only formulations of hormonal contraception have vascular risks that are undetectable with modern epidemiologic methods. Although hormonal contraception is not risk-free, the evidence is convincing that the low and very low doses of ethinyl estradiol (<50 μg) in the combined estrogen–progestin contraceptives studied by Lidegaard and colleagues — whatever the progestin and whether delivered orally or by means of the patch or the ring — are safe enough.

How you can use this data in making contraceptive choices

If you don’t want vascular risks, however small, stick with a progestin only method. The price you’ll pay is some degree of menstrual irregularity, whether its unpredictable bleeding (Impanon), breakthrough bleeding (POP’s, Mirena, Depo- Provera) or over time, no periods at all (Mirena, Depo-Provera).  Progestin only methods also may not benefit skin the way estrogen-containing methods do, and some (like Depo-Provera) can lead to weight gain.   POP’s have slightly less efficacy that estrogen-containing methods and the other progestin-only methods.

If you’re willing to accept the small but real vascular risks of estrogen containing contraceptives, you can potentially minimize that risk by starting with a 10ug or 20 ug pill. These pills do have higher rates of breakthrough bleeding than the 30 ug and higher methods.  Some studies have suggested that in obese women, more perfect compliance is needed to maintain efficacy with these pills meaning you have less leeway to miss a pill occasionally than a thinner woman. Other studies have suggested that these ultra low dose pills may not be as good for bone protection in teens, who are building bone they will need for their adult lives.

If remembering to take a pill is your issue, and you’re not willing to accept the menstrual cycles changes associated with the long acting progestin only methods, consider the ring or patch.  You’ll be accepting a slightly higher risk of vascular side effects, but if you’re under age 40, those risks are exceedingly low.

If you are over age 40,  progestin-only  methods and the lower dose estrogen-containing methods are good first line choices. Women without risks for heart disease remain good candidates for estrogen-containing hormonal contraception, and the pill in particular can ease the perimenopausal transition.

The above is just a rough outline of one approach to take. There are as many options and choices to make as there are individual woman. Other considerations, such as cost, availability, previous experience with a given method, other medical and gynecologic conditions,  other side effects and personal preference need to be taken into account in making contraceptive choices.

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Good reporting on this story

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