IIT Madras Study: Oral Contraceptives Don't Raise BP During Intense Workouts

Chennai: Oral contraceptives do not increase the blood pressure response in women during large muscle exercises like cycling or running, according to a recent study led by researchers at the Indian Institute of Technology (IIT) Madras.

Birth control pills, commonly used by women to prevent pregnancy, manage acne, relieve menstrual cramps, and reduce the risk of ovarian cysts, are known to raise resting blood pressure in some cases. However, how these contraceptives influence blood pressure during intense physical activities has remained unclear.

The study, conducted in collaboration with the University of Minnesota, examined the effects of oral contraceptive use and natural hormonal fluctuations on blood pressure during exercise in young women aged 20-25. The findings revealed that neither oral contraceptives nor changes in ovarian hormone levels, such as estrogens, significantly influenced the blood pressure response during exercise.

Furthermore, the study observed similar results during lower-body workouts and exercises that activate skeletal muscle sensory neurons. These neurons, known to regulate blood pressure during physical exertion, often exhibit exaggerated responses in individuals with cardiovascular diseases.

Exercise naturally raises blood pressure due to increased sympathetic nerve activity, a response driven by the "Exercise Pressor Reflex" (EPR). This reflex ensures adequate blood flow from the heart to the working skeletal muscles. The EPR is generally more pronounced in men than in premenopausal women and is often heightened in individuals with cardiovascular issues.

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.”

Estrogen, a cardioprotective hormone, is known to mitigate sympathetic activity and enhance blood flow to muscles through nitric oxide bioavailability. Researchers hypothesized that during the ovulation phase, when estrogen peaks, women would exhibit the lowest EPR. This response was expected to differ from women in the early follicular phase when estrogen is at its lowest, and from those using oral contraceptives, which lower serum estrogen levels.

However, the study found that regardless of the menstrual cycle phase or oral contraceptive use, the EPR remained consistent across all participants. This suggests that oral contraceptives do not heighten blood pressure responses during exercise compared to women who do not use contraceptives.