IIT Madras study finds oral contraceptives do not raise BP in women during intense workout

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Oral contraceptives do not increase the blood pressure response in women during large muscle exercise (like cycling or running), according to a study on Monday led by researchers from the Indian Institute of Technology (IIT) Madras.

Oral contraceptives or birth control pills are taken by women to prevent pregnancy and reduce acne, menstrual cramps, and the risk of ovarian cysts.

Although certain oral contraceptives are known to raise resting blood pressure, the exercise blood pressure response during intense exercises is not currently well understood.

In addition, research has been ambiguous on whether hormonal fluctuations during the menstrual cycle influence blood pressure.

The researchers, including from the University of Minnesota, US, found that both oral contraceptive use and general fluctuations in endogenous ovarian hormone (like estrogens) in young women (20-25 years of age), did not influence blood pressure.

The results were similar with lower body exercise and activation of skeletal muscle sensory neurons -- known to contribute to exaggerated blood pressure responses in people with cardiovascular diseases.

"The findings of this study have wide application and are important as it sheds light on the influence of oral contraceptives on blood pressure response to exercise in women," said Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras.

Exercise can acutely increase blood pressure due to increased sympathetic nerve activity (fight or flight) from skeletal muscle sensory neurons known as ‘Exercise Pressor Reflex' (EPR).

The EPR results in an increase in blood flow from the heart to the skeletal muscle to meet the needs of the muscle. The EPR is known to be greater in males compared with premenopausal females and is also known to be exaggerated in people with cardiovascular disease.

Estrogens are cardioprotective, they reduce sympathetic activity and increase blood flow to the skeletal muscle via nitric oxide bioavailability.

Thus, the researchers expected that during the ovulation phase of their menstrual cycle, when oestradiol peaks, women would have the lowest EPR compared with females during the early follicular phase (where oestradiol is the lowest) and with oral contraceptive use, which also results in low serum oestradiol levels.

However, the researchers demonstrated that regardless of the phase of the menstrual cycle or oral contraceptive use, the EPR was similar in the women.

This suggests that oral contraceptives do not increase the blood pressure response in women more so than in those who do not use oral contraceptives, revealed the findings, published in the reputed peer-reviewed journal American Journal of Physiology-Regulatory, Integrative and Comparative Physiology.

"The next step of this work is to determine if the EPR is a contributing factor to the cardiovascular risk in menopausal females," said Dr. Manda Keller Ross, Assistant Professor at the University of Minnesota.

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