New research citing an increased risk of heart disease among women who take -- or who have ever taken -- birth control pills is reigniting debate over the true connection between the birth control drugs and cardiovascular ills.
Researchers from Ghent University in Belgium looked at 1,301 apparently healthy women between the ages of 25 and 55 who had previously used oral contraceptives, half of whom used them for 13 years or more. What they said they found was that women who had used the pills had an unexpected increase in the presence of artery-clogging plaque in key blood vessels supplying the brain and legs.
On average, the researchers said the women had a 20 to 30 percent increase in plaque for every 10 years they had taken oral contraceptives. They presented their findings at the American Heart Association scientific sessions in Orlando, Fla., on Tuesday.
But past research on the possible connection has been far from conclusive.
At least two recent studies have suggested such a link does not exist. One, a Swedish study published in August on the second- and third- generation oral contraceptives currently used by most women, showed that women who were currently on the pills and those who had modern pills did not have a higher risk of heart attack.
And researchers in the WISE study group at the Cedars-Sinai Research Institute in Los Angeles completed a study of 672 postmenopausal women in 2006 that showed that past oral contraceptive use not only didn't increase the chances of coronary artery disease, but actually protected women from such heart ills.
Lead author of the WISE study Dr. Noel Bairey-Merz conceded that her study looked at a different population -- postmenopausal women with an average age of 60.
But she said that current evidence does not suggest that women taking oral contraceptives have an increased risk of heart disease once they pass menopause.
"So that's an example of something you measure when women are 35 years old that doesn't always predict what they're going to be like when they're 65," she said.
Conversely, two earlier metaanalysis studies (those which compile the results of previous studies) suggest that the pill -- or at least the older versions of the pill -- are linked to an 80 percent to 200 percent increased risk of heart attack in women currently using them.
In light of this, some doctors say, the only sure conclusion that can be made is that the exact link between oral contraceptives and heart problems will likely continue to be a controversial one.
"This new Belgium study does not provide a definitive answer to the question of whether or not past oral contraceptive use actually increases the risk of having a heart attack," said ABC News Medical Editor Dr. Tim Johnson. "Other studies addressing this question are contradictory.
"So this is a situation where the old cliché is really true -- we need more study."
New Study, Old Debate
If one thing is for certain, it is that any relationship between oral contraceptives and heart ills would have direct implications for millions of women. According to the Centers for Disease Control and Prevention, oral contraceptives are the most common type of birth control, used by 11.7 million women.
Doctors have already known that oral contraceptives increased blood pressure and the risk of blood clots in women who took them -- a risk that is even higher in women who smoke.
But researchers involved with the new study say the findings concerning the formation of cholesterol plaques within arteries is a new one.
"The implications could be that you have higher stroke or heart attack rate," said lead study investigator Dr. Ernst Rietzschel of Ghent University, who noted that he was "surprised" at the findings.
"What we knew was that there was a risk of forming clots from taking pill, but once you stopped you had no residual risk," he said. "Our data show that if you take the pill for a long time you have accumulation of damage that gives you risk even after stopping."
Some physicians not involved with the research agreed that the results are intriguing.
"I think this is sort of a wake-up call for women and their physicians," said Dr. Jennifer Mieres, associate professor of medicine and director of nuclear cardiology at the New York University School of Medicine.
"It is a staggering statistic that there is a 20 to 30 percent increased risk in plaque formation in women who had used the pill for a decade, which becomes evident at a relatively young age," said Dr. Suzanne Steinbaum, director of Women and Heart Disease at the Lenox Hill Hospital's Heart and Vascular Institute in New York, N.Y.
"Certainly, like hormone replacement therapy recommendations are qualified in certain patients who are at risk for breast cancer, the recommendation for using the pill might need to be changed in those patients who are at risk for heart disease, and perhaps they should use another form of birth control," she said
However, not all heart physicians agreed that the findings broke new ground.
"If the author says it's the first shown cardio risk after discontinuation, I don't think that's true," said Dr. Camelia Davtyan, assistant professor of general internal medicine and health services research at the David Geffen School of Medicine at UCLA. Davtyan also cited the WISE study, which appeared to reach an entirely opposite conclusion.
Some other doctors were also hesitant to accept the findings as legitimate.
"It is new, unique data, and it definitely flies in the face of what we've been telling women based on past data," said Dr. Sharonne Hayes, director of the Women's Heart Clinic at Mayo Clinic in Rochester, Minn.
"It is a bit weak and needs to be replicated prospectively, or at least in other populations, since all -- and I mean decades of observational study -- say there is no increased risk of [heart-related] events with past use of [oral contraceptives]."
"Interpreting cross-sectional studies such as this one can be very complicated," said Dr. David Herrington, professor of medicine and cardiology at the Wake Forest University School of Medicine in Winston-Salem, N.C.
"These data are provocative and need to be confirmed or refuted in other cohorts, prospective data and clinical trials," he continued. "In isolation, these data do not provide enough evidence to make a general statement about the long term vascular effects of [oral contraceptive] use."
Women Should Not Change Regimens -- Yet
Most doctors -- Rietzschel included -- agreed women on the pill should not panic, as more data is needed before doctors can make recommendations based on this new evidence.
"For women taking third-generation pills today, we aren't sure what the implications are," he said.
Davtyan concurred. "Basically I would not tell people to stop using contraceptives right this moment and I think this would really have to be confirmed."
Rather, Rietzschel added, women should become more aware of other lifestyle factors that they can change in order to lower their overall risk of heart disease.
"The implications are that you shouldn't suddenly stop taking [oral contraceptives], no reason to panic, but look at your risk factors," he said. "Is there something you can do to prevent heart disease in the future? Avoid obesity, stop smoking, be physically active, et cetera.
"So don't stop taking the pill, but limit the risk of heart disease through primary preventive measures we all need to take."
Roger Sergel, ABC News' managing editor for medical coverage, and Audrey Grayson contributed to this report.