Men Are Five Times as Likely as Women to Have This Cancer-Causing STD

Human papillomaviruses (HPVs) are a collection of more than 200 related viruses, many of which are easily spread through sexual contact. HPV infections are the most common sexually transmitted infection in the United States and the Centers for Disease Control and Prevention estimates that more than 90 percent of sexually active men will be infected with at least one type of human papillomavirus (HPV) during their lives.

There are two types of sexually transmitted HPV: low-risk HPVs can cause genital warts, while high-risk HPVs can cause cancer. In fact, they're responsible for virtually all cases of cervical cancer and 95 percent of cases of anal cancer. They also cause about 70 percent of oropharyngeal cancers, which attack the middle part of the throat, including the soft palate, the base of the tongue, and the tonsils. The most common cancer linked to HPV infection is oropharyngeal squamous cell carcinoma (OPSCC), a type of head and neck cancer that's especially prevalent in men.

Now, a new study published in Annals of Internal Medicine finds that about one in nine American men (or 11.5 percent) is infected with oral HPV, nearly four times the rate for women (3.2 percent). That amounts to an estimated 11 million men with HPV nationwide, including both high- and low-risk categories of HPV. The researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES), in which a nationally representative sample of adults got physicals at mobile examination centers between 2011 and 2014. Everyone was tested for oral and genital HPV.

High-risk oral HPV infection was also more prevalent among men than women: 7.3 percent versus 1.4 percent, respectively; a risk of five times greater. One high-risk type, HPV 16, was six times as likely to strike men than women—almost two million men are estimated to be infected.

Besides differences in oral HPV infection rates between sexes, the study also looked out how sexual behavior was linked to infection rates by using questionnaire data from the NHANES study. Men who had same-sex partners had a nearly 13 percent chance of high-risk infection; among women with same-sex partners, the number was 3.6 percent. For men who'd had two or more oral sex partners, that number was 22.2 percent. And men who had a genital HPV infection were four times as likely to also have an oral infection as those who did not.

Ultimately, the study found, the predicted probability of high-risk oral HPV was highest among black participants, anyone who smoked more than 20 cigarettes a day (smoking increases the risk of oral HPV infection), people currently using marijuana (it's possible that chemicals in weed affect the immune system, allowing HPV infections to linger though there are other theories), and people who reported 16 or more vaginal or oral sex partners.

Watch More From Vice News Tonight:

That high-risk population should be the focus of prevention strategies, says Ashish A. Deshmukh, assistant research professor at the University of Florida college of public health and the study's lead author. "The most important takeaway from this study is that we need to have certain prevention measures among these individuals. The most important thing is HPV vaccination," he tells Tonic. At-risk groups should also receive extra attention, including screening.

The CDC recommends vaccinations at age 11 or 12, though kids can get the series of shots starting as early as 9. The idea is for parents to get their kids vaccinated long before they're exposed to HPV through sexual activity. Anyone who hasn't been previously vaccinated can get the shots up to age 21 for men and age 26 for women and gay and bisexual men and immunocompromised people. (You can still get them after that, but insurance won't cover it.) According to the CDC, HPV causes about 31,500 cases of cancer a year, most of which could be prevented by vaccinations.

Deshmukh points out that vaccination rates rates have increased overall, but remain shockingly low among men—a study released last year found that, among adults aged 19 to 26, more than 40 percent of women were vaccinated in 2014, compared to just 8.2 percent of men. Vaccination rates for boys have improved in the last few years, alongside rates overall. But some studies show that parents with no interest in vaccinating their sons were largely unaware of the risks HPV poses to men. "Boys are still not getting HPV vaccinations," he says. "I believe that we need to have educational outreach, especially teaching parents to vaccinate the boys."

As to why men have such high rates of oral HPV infection, Deshmukh says there are a few possible explanations. In most cases, HPV goes away on its own and doesn't lead to any health problems but HPV infections may stay with men longer, leading to higher rates of the STD. Men may also acquire oral HPV more readily via sex than women do and, to add insult to injury, they may produce fewer antibodies after a genital HPV infection than women, which would give men less protection against a future oral HPV infection. This one-two punch would leave women relatively better protected.

That makes vaccinations all the more important for men. Deshmukh noted that those at highest risk for oral HPV are actually among those too old for the vaccine—the recommended cutoff is 26 years old, though older patients can request the shots. Right now, he said, vaccination is the most powerful tool for preventing infection, and it needs to be a higher priority.

Read This Next: A Shot Could Have Prevented the Cancer That's Killing Me