April 11, 2003 -- Birth control pills appear to be associated with increased levels of a protein linked to heart disease. In a newly reported study, young women who took birth control pills had twice as much C-reactive protein in their blood as a similar group of women who did not use birth control pills.
The findings, while preliminary, could help explain a reported increase in heart disease among birth control pill users. C-reactive protein (CRP) is produced in the liver in response to inflammation. Chronically high CRP has been linked to heart disease, and inflammation is believed to play a key role in narrowing and hardening of the arteries.
"It is possible that oral contraceptive use promotes inflammation," researcher Darlene M. Dreon, DrPH, of Galileo Pharmaceuticals tells WebMD. "Hormone replacement therapy has also been linked to higher CRP levels in postmenopausal women." All of this suggests that estrogen hormones may increase inflammation, she adds.
Dreon and colleagues measured CRP levels in blood samples from 30 premenopausal women. Eighteen of the women were taking birth control pills and 12 were not. All of the women were healthy non-smokers who were not obese. Those on birth control pills took low-dose progestin preparations similar to those most often prescribed today. The findings were reported in San Diego this week at the annual meeting of the American Physiological Society.
Plasma CRP levels were twice as high among the birth control pill users, even though other risk factors for heart disease were similar to those seen in the women not on birth control pills. But CRP levels in both groups were considered in the normal range, leading the researchers to conclude that more research is needed to determine the clinical significance of the findings.
"We know nothing about what CRP levels mean in younger populations that aren't at risk for coronary artery disease," Dreon says. "This was a small study, and it certainly doesn't prove cause and effect."
Gynecologist and contraceptive specialist Trent MacKay, MD, agrees. He says the fact that both groups had normal CRP levels suggests that, for younger women at least, birth control pill use is of little clinical significance in terms of heart disease risk. MacKay is special assistant for obstetrics and gynecology in the Contraception and Reproductive Health Branch of the National Institutes of Health.
The only women who clearly need to worry about birth control pill use and heart disease risk, he says, are those who are over the age of 35 and are also heavy smokers.
"For everyone else, the association between oral contraceptive use and heart disease is weak, at best," he tells WebMD. "Women under the age of 35 are not at particularly increased risk, even if they smoke. The fact is, cardiovascular disease is a disease of aging, and aging women do not use oral contraceptives."