Discussion: Are There Cardiovascular Benefits to the Use of Estrogen-free Oral Contraceptives in Women?

In this video, Michael J. Bloch, MD, discusses any cardiovascular benefits to the use of estrogen-free oral contraceptives in women, including a recently published study on the association of menstrual cycle regularity and length with cardiovascular diseases. This is part 3 of a 3-part discussion series on oral contraceptives in women and cardiovascular disease.

Additional Resource:

• Huang C, Lin B, Yuan Y, et al. Associations of menstrual cycle regularity and length with cardiovascular diseases: a prospective study from UK Biobank. J Am Heart Assoc. 2023;12(11):e029020. doi:10.1161/JAHA.122.029020

For part 1 of this 3-part series, visit here.

For part 2 of this 3-part series, visit here.

Michael J. Bloch, MD, is an associate professor at the University of Nevada School of Medicine, the medical director of vascular care at the Renown Institute for Heart and Vascular Health, and the President of Blue Spruce Medical Consultants, PLLC (Reno, NV).

TRANSCRIPTION:

Dr Michael J Bloch: Hello. My name's Dr  Michael Bloch. I'm a vascular medicine provider from Reno, Nevada. In a previous posting, I talked in some detail about the methodology and results of a recent study that was published in the Journal of the American Heart Association, which came out of the UK Biobank and demonstrated that women who had a history of irregular menstrual cycles had a modestly increased risk of subsequent cardiovascular events than women who had normal menstrual cycles. The effect, though, I think was relatively modest, but it does have some implications for clinical practice. I think one of the first things to really keep in mind with looking at data like this is that although the UK Biobank is a great repository of clinical information, it is an observational study. So although there is some proof of an association, that certainly does not in any way prove causation. Women who had irregular menstrual cycles did seem to have a higher baseline prevalence of other cardiovascular risk factors like smoking and dyslipidemia and hypertension.

However, in multivariate analysis, even when those things were corrected for, the association still mostly held. I think it's also important to recognize that the association was strongest for atrial fibrillation, much stronger for atrial fibrillation than it was for other, what we would call, harder cardiovascular events like coronary artery disease, myocardial infarction, stroke, or heart failure. The other, I think, important caveat when looking at this study is that the absolute number of events was low. So the incidents of a subsequent cardiovascular event over 12 years of follow-up in the women who had a history of irregular menstrual cycles was about 3.5% as compared to about 2.5% in patients who had more regular menstrual cycles. So certainly was a statistically significant 20% approximately increase in cardiovascular events, but when you look at the number needed to harm because of those low event rates, the number needed to harm was 100.

So if provider A has 100 women who have essentially regular menstrual cycles, provider B has 100 women who have irregular menstrual cycles, and they both follow those women for 12 years, provider B will have one more cardiovascular event than provider A, so a modest difference in events. That being said, I still think that it is important to recognize and talk about a history of irregular menstrual cycles as a potential cardiovascular risk factor. And if we do identify that history, we should be getting that history. And if we identify that history, perhaps we should be treating other cardiovascular risk factors like hypertension and diabetes and smoking and dyslipidemia more aggressively in women who have a history of irregular menstrual cycles. I think one of the other intriguing things about this study is what it means about the association between estrogen exposure and the risk of cardiovascular events, particularly the risk of atrial fibrillation.

It has been assumed that women who have more regular menstrual cycles may have higher estrogen levels, and if that's in fact the case, that may have been the cause for the reduced cardiovascular events in this population. And that link between estrogen exposure and atrial fibrillation really hasn't been explored very much before and is probably something that we should think about for future clinical trials. Whether or not this really means anything for women who have a history of oral contraceptive exposure or how we should be changing perhaps exposure of women to estrogen-containing oral contraceptives, I think is really unknown, OCP use was relatively low, at least at baseline, in this patient population and really wasn't looked at very carefully in this study. So in summary, I think this is very interesting data that does show that women with a history of irregular menstrual cycles do have a modestly increased risk of cardiovascular events as compared to those who had normal menstrual cycles, but the absolute difference is relatively low.

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