An intriguing new study finds a link between human papillomavirus, or HPV, the common sexually transmitted infection that is the cause of most cervical cancer, and an increased risk of heart attack and stroke in women.
Led by Dr. Kenichi Fujise of the University of Texas Medical Branch in Galveston, Texas, the study found that women who tested positive for any strain of HPV were 2.3 times more likely to have had a heart attack or stroke than women who tested negative. Women who tested positive for high-risk strains of HPV, those known to cause cancer, had an even higher risk of heart attack or stroke, 2.86 times higher than uninfected women.
The study included 2,450 women, aged 20 to 59, who had participated in the Center for Disease Control and Prevention’s (CDC) National Health and Nutrition Examination Survey between 2003 and 2006. The participants were tested for HPV — 44.6% tested positive for any strain of HPV, and 23.2% tested positive for a high-risk strain — and reported their heart-disease status. In total, 1,141 women had HPV. Sixty said they’d had a heart attack or stroke, and 39 of these women had HPV.
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The researchers focused on HPV in hopes of finding a clue to why some people develop heart disease, even though they don’t have traditional cardiovascular risk factors like high blood pressure, obesity or a history of smoking — about 20% of heart disease patients. HPV seemed like a plausible candidate since the virus interferes with the function of a gene called p53. Inactivation of the tumor-suppressing gene contributes to various cancers, but previous research has shown that p53 also regulates atherosclerosis, or hardening of the arteries; disabling it could also lead to inflammation and worsen artery health.
HPV inactivates another tumor-suppressing gene called retinoblastoma protein, which regulates the growth of smooth muscle cells that line blood vessels, so interfering with its function could also affect blood flow and therefore heart attack risk.
While the new study’s findings are interesting, they show only an association. They don’t prove that HPV causes heart disease. It’s possible, for example, that women with heart disease are predisposed to HPV infection, rather than vice versa, or that some other underlying factor makes women vulnerable to both.
A great deal more study is necessary before a link between HPV and cardiovascular risk can be definitively established. As the New York Times reported:
“We need to proceed with caution,” Dr. [Lori] Mosca, [director of preventive cardiology at NewYork-Presbyterian Hospital/Columbia University Medical Center, who was not involved with the study,] said. “We need to go on and do more rigorous kinds of research that would answer the question more definitively.”
She said that many researchers were studying possible links among cancer, infections and heart disease, but that so far no infection had been proved to cause artery disease.
Dr. Fujise’s work, she said, “has the potential, if it does pan out, to further inform the public about the potential benefits of vaccination for HPV.” But she added that the findings were too preliminary to be used as evidence in favor of vaccination.
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HPV is the most common sexually transmitted infection in the U.S., affecting at least half of all sexually active men and women at some point. By age 50, 80% of sexually active women have had HPV. Most people clear the infections on their own, but in a small minority of cases, infections may persist and lead to cancer. The HPV vaccine, which protects against genital warts and cancers of the cervix, vulva, vagina, penis, anus and throat, is recommended for both boys and girls aged 11 and 12.
If further study confirms the association between HPV and heart disease, it could help shed valuable light on why people without the usual heart risk factors have heart attacks anyway. Each year, 510,000 women have heart attacks in the U.S., according to the American Heart Association. If HPV is confirmed to play a role in heart risk, MSNBC reported, Fujise calculates that 4,321 of women could be having heart attacks each year due to HPV rather than other risk factors, and that 1,618 women are dying every year from HPV-related heart attacks.
The study was published in the Journal of the American College of Cardiology.
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Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.