IIT Madras & US Researchers Study Oral Contraceptives' Effects on Women's Blood Pressure

IIT Madras and University of Minnesota researchers study how oral contraceptives affect blood pressure in women during dynamic exercises. Check details here

IIT Madras & US Researchers Study Oral Contraceptives

Researchers from the Indian Institute of Technology (IIT) Madras and the University of Minnesota, U.S., are studying the effects of oral contraceptives on blood pressure in women engaging in dynamic exercises. The study is led by Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras, alongside Dr. Manda Keller Ross and Miguel Anselmo from the University of Minnesota. Dr. Ninitha is supported by the Science and Engineering Research Board’s ‘Core Research’ Grant, while Prof. Manda Keller Ross receives funding from the National Institutes of Health (NIH), U.S.

Oral Contraceptives' Impacts on Women's Blood Pressure

Some oral contraceptives are known to elevate resting blood pressure, but their impact on blood pressure during dynamic exercises like cycling or running remains unclear. Additionally, the influence of hormonal fluctuations during the menstrual cycle on blood pressure has been inconclusive. The research team found that in young women aged 20-25, neither oral contraceptive use nor natural fluctuations in ovarian hormones, such as estrogen, affected blood pressure during lower-body exercises. They also observed no impact on the activation of skeletal muscle sensory neurons, which are typically associated with heightened blood pressure responses in individuals with cardiovascular conditions.

Exercise temporarily raises blood pressure due to increased sympathetic nerve activity from skeletal muscle sensory neurons, known as the ‘Exercise Pressor Reflex’ (EPR). The EPR enhances blood flow to muscles and is typically stronger in males and individuals with cardiovascular disease compared to premenopausal females. Estrogens, being cardioprotective, lower sympathetic activity and boost muscle blood flow through nitric oxide.

Researchers hypothesized that women would show the lowest EPR during the ovulation phase, when estradiol peaks, compared to the early follicular phase or during oral contraceptive use, both of which result in low estradiol levels. The researchers found that the EPR remained consistent in women, regardless of their menstrual cycle phase or oral contraceptive use. This indicates that oral contraceptives do not amplify the blood pressure response compared to women who do not use them.

The results of this study indicate that neither endogenous nor exogenous (OC) sex hormones modulate BP during lower extremity dynamic exercise or with group III/IV afferent activation in young, healthy females.

Elaborating on this research, Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras, said, “Oral contraceptives or birth control pills are taken by women to prevent pregnancy, reduce acne, menstrual cramps, and risk of ovarian cysts. According to a study by Martin and colleagues, around 70 % of female athletes took oral contraceptives at a point in their career and thus it is important to understand how they affect blood pressure. The findings of this study have wide application and are of importance as it sheds light on the influence of oral contraceptives on blood pressure response to exercise in women.”

Further, Dr. Manda Keller Ross, Assistant Professor at the University of Minnesota, Minneapolis, U.S., added, “We have little information on how the EPR changes in women across the life span. Menopause, the cessation of hormone production in the ovaries, occurs at around 50 years old and cardiovascular risk increases in women throughout and after the menopause transition. The next step of this work is to determine if the EPR is a contributing factor to the cardiovascular risk in menopausal females.”

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