CHAPEL HILL - Oral contraceptives are known to increase the risk of heart problems for smokers, and new research at the University of North Carolina at Chapel Hill suggests that might be due in part to the specific type of hormones contained in "the pill."
Older "second-generation" oral contraceptives have a higher androgenic content because of the type of progesterone hormone used when compared to newer "third-generation" formulations.
For all women, older oral contraceptives produced higher blood pressures and more resistance to blood flow inside blood vessels during stressful situations, the UNC-CH School of Medicine study shows.
A report on the findings appears in the January issue of Obstetrics and Gynecology, a medical journal. Authors include psychology graduate student Patricia Straneva and Dr. Susan Girdler, assistant professor of psychiatry.
The UNC-CH study involved extensive testing of physiologic reactions of healthy women taking two different types of oral contraceptives, including 23 smokers and 23 nonsmokers, at rest and during mental and physical stress. Researchers induced stress by having volunteers perform rapid calculations, prepare and present short speeches and sit with a plastic bag of ice held to their foreheads for two minutes.
"Among smokers we found lower cardiac output, meaning that their hearts were pumping less blood, and greater vascular resistance, meaning that there was more tension in the blood vessels resisting blood flow," Straneva said. "This was not surprising considering the harmful effects of smoking on the heart."
Subjects who smoked and took older, more androgenic oral contraceptives showed the highest blood pressures and vascular resistance during stress, she said. All of the women, who were in their mid-20s, were healthy and had normal blood pressures when not under stress.
"Based on our findings, the type of progesterone should be an important consideration when determining which oral co
Contact: David Williamson
University of North Carolina at Chapel Hill