We already know HPV, or human papillomavirus, can cause cervical cancer. It's also known to cause some kinds of oral cancer.
But could HPV also cause heart disease? An intriguing new study is drawing a link.
The study found that women who are known to be infected with cancer-causing strains of the virus may be at increased risk for cardiovascular disease and stroke -- even when they have none of the usual heart disease risk factors.
The study authors say their research is one of the first to investigate a potential link between heart disease and HPV, which is one of the most common sexually transmitted infections.
The Public Health Agency of Canada estimates that more than 70 per cent of sexually-active Canadian men and women will have a sexually transmitted HPV infection at some point in their lives.
They say they began the study because they wanted to know why some people have heart attacks even though they have none of the usual risk factors, like high cholesterol or high blood pressure.
About 20 per cent of patients with heart disease lack risk factors, which has left open the possibility that underlying "nontraditional" causes might be involved in the disease.
If there is indeed a link between the virus and heart disease, it could have a number of implications. It would mean that doctors would have to monitor patients with HPV to help prevent heart attack and stroke.
As well, there is the possibility that the HPV vaccine might also help prevent heart disease.
The study looked at nearly 2,500 women between the ages of 20 and 59 using data from the 2003-2006 National Health and Nutrition Examination Survey (NHANES).
Among the study volunteers, 44.6 per cent were positive for the genetic material of HPV DNA, including 23.2 per cent who had known cancer-causing strains of the virus.
The researchers broke the women into groups: those with cancer-causing HPV strains; those with other HPV types; and those who were not infected.
They then looked at their history of heart disease, their heart disease risk factors, and their age, race, and lifestyle habits.
They found that cancer-causing strains of HPV were "strongly associated" with heart disease, but didn't link HPV and other metabolic risks.
"Further, the link persevered after adjusting for cardiovascular risk burden and management, other medical conditions and health and sexual behaviors," said Dr. Hsu-Ko Kuo, co-author of the study, which appears in the Journal of the American College of Cardiology.
If HPV does play a role in heart disease, the authors say it might be due to HPV's role in inactivating two tumour suppressor genes, called p53 and retinoblastoma protein (pRb). The inactivation of those two genes is the same way that HPV is thought to cause cancer.
As well, p53 has been shown to be essential in regulating the process of atherosclerosis; the gene affecting retinoblastoma protein plays a pivotal role in regulating cell proliferation.
Dr. Eduardo Franco, director of the Division of Cancer Epidemiology at McGill's Faculty of Medicine reviewed the study and says he finds the suggestions that HPV and heart disease could be linked "is not plausible" given what is known about the way different strains of HPV interact with their target cells.
He also found the high rate of HPV infection in the women "suspicious" because, given the ages of the women, the rates should have been much lower.
"Overall, this suggests errors, possibly due to contamination of specimens either during collection or pre/post-processing," he said in comments to CTV News.
He suggested the researchers did not properly consider the marital status of the women, which might have accounted for the link they found between HPV and heart disease.
"Women (and men) without stable marital relations (and thus prone to stress that comes from the lack of a family support unit) are at greater risk of (heart disease). They are also the ones most likely to acquire HPV infection from multiple sexual encounters," he said.
