Women infected with cancer-causing strains of the human papillomavirus (HPV) appear also to be at increased for cardiovascular diseases and stroke, even in the absence of other more conventional risk factors, according to new research published in the 1 November issue of the Journal of the American College of Cardiology.
Lead author Dr Ken Fujise, Director, Division of Cardiology at University of Texas Medical Branch (UTMB) at Galveston, told the press that nearly 20% of people who develop cardiovascular disease show none of the traditional risk factors normally associated with it, suggesting there are some “non-traditional” risk factors.
“HPV appears to be one such factor among women,” he suggests.
“This has important clinical implications. First, the HPV vaccine may also help prevent heart disease. Second, physicians should monitor patients with cancer-associated HPV to prevent heart attack and stroke, as well as HPV patients already diagnosed with CVD to avoid future cardiovascular events,” says Fujise.
The study is thought to be the first of its kind to examine the link between cardiovascular disease and HPV, one of the most common sexually transmitted infections in the US.
In their study, Fujise and co-author Hsu-Ko Kuo, an internist at UTMB, looked at records from the 2003-2006 National Health and Nutrition Examination Survey (NHANES). These included a subset of data from nearly 2,500 women aged 20-59 who took their own vaginal swabs that were then later genotyped to see if they contained HPV DNA.
Looking at this data subset, Fujise and Kuo found that 44.6% (1,141 samples) had tested positive for HPV with 23.2% (573) showing they had cancer-causing strains.
Then, by adding data from other female survey participants, they compared results from women with cancer-causing HPV with women with other types of HPV and also women who had not tested positive for HPV at all.
The data included questionnaire responses about cardiovascular disease history, blood pressure and high blood pressure, BMI, blood glucose, blood fats, cholesterol, diabetes and other conditions. They also had available the usual demographic and clinical information such as age, race, smoking status and alcohol intake.
Fujise and Kuo found that cancer-causing HPV types were strongly linked to cardiovascular disease, but they didn’t see a link between HPV and other metabolic risks.
Even after they adjusted for known cardiovascular risks, other medical conditions and sexual behaviors, the link persisted, they say.
Since the study was of a cross-sectional design (comparing different participants at the same point in time), it is not possible to draw conclusions about cause and effect between presence of HPV and cardiovascular disease risk.
But Fujise says:
“While we’re not certain if there is a cause and effect relationship between the two, there is a clear-cut association – with serious public health significance.”
Also, he and Kuo offer a plausible biological explanation for such an effect.
We already know that cancer-causing HPV switches off genes that normall stop tumors from forming: these genes are p53 and retinoblastoma protein (pRb).
But p53 also has another function, it helps control atherosclerosis (the process that leads to blocked arteries).
Fujise says if we can prove HPV activates p53’s other function, then a drug that stops p53 from being switched off could help prevent cardiovascular disease in women who are already infected with HPV.
He and Kuo recommend:
- A re-examination of results from randomized clinical trials of HPV vaccines to look for cardiovascular effects.
- Arranging a clinical trial to see if HPV immunization reduces heart problems in women.
- Finding out more about the biology that links HPV infection with atherosclerosis, with particular emphasis on looking more closely at how HPV interacts with p53 and pRb (there are more than 100 strains of HPV but so far studies have only focused on 2 of them).
- Doing a follow up study looking at cardiovascular outcomes in individuals infected with HPV and those not infected, to see if there is evidence that HPV causes cardiovascular disease.
- And last but not least, looking at the link between HPV and cardiovascular diseases in men.
Fujise says because the data they analyzed came from self-collected swabs, and also self-reported cardiovascular events and illnesses, it may not fully reflect actual prevalence of the condition, suggesting the link between HPV and cardiovascular risk could be even stronger than what they found.
“With more research, improved understanding of HPV as an independent factor in CVD may lead to improved patient outcomes – a crucial advancement because heart disease is the number one killer of women,” says Kuo.
Written by Catharine Paddock PhD