About one in nine American men is infected with the oral form of human papillomavirus (HPV), according to a new study published in the journal Annals of Internal Medicine. Nationwide, rates for oral HPV infections are 11.5% of men and 3.2% of women: 11 million men, compared with 3.2 million women, the researchers estimated.
An infection with this common virus, which is transmitted through intimate skin-to-skin contact, can cause cancer in several areas of the body, including the throat, anus, penis and vagina. Nearly all men and women will become infected with at least one type of HPV, a group of 150 related viruses, at some point in their lives, according to the US Centers for Disease Control and Prevention.
Previous studies have shown that men have higher rates of overall HPV infections than women. The research published Monday reveals the higher rates of oral HPV infections occurring among men, said Ashish A. Deshmukh, senior author of the study and an assistant professor at the University of Florida's College of Public Health and Health Professions.
"One suspects that the HPV persists longer (means doesn't clear easily) among men and that might be causing increased prevalence," Deshmukh noted in an email.
"It is also possible that men acquire oral HPV more readily than women," he said. Yet another possibility could be that, after a first infection, women develop greater resistance to subsequent infections. "Further research is needed to understand the reason behind this," Deshmukh added.
A warning to men
Annually, an average of 38,793 cases of HPV-related cancer -- 59% of them in women and 41% in men -- were diagnosed in the United States between 2008 and 2012.
Yet, in each year within that time span, a type of head and neck cancer called oropharyngeal squamous cell carcinoma was far more likely to strike men: 12,638 cases diagnosed in men each year, compared with just 3,100 cases in women.
It is the most common of all the HPV-related cancers, and its incidence among men (7.8 per 100,000) now surpasses incidence rates of cervical cancer among women (7.4 per 100,000). Cervical cancer is known to be caused by HPV.
An HPV vaccine is available for both men and women and can protect against infection, yet many men are over the eligibility age of 26, and younger men have low vaccination rates. The CDC recommends the vaccination for adolescents.
Deshmukh and a team of researchers used data from the National Health and Nutrition Examination Survey to look at oral HPV infection rates in addition to how many men and women have both oral and genital HPV.
This CDC survey monitors the health and nutritional status of the nation's population. Participants between the ages of 18 and 69 were given a physical examination, which included laboratory tests for 37 HPV types, followed by an interview.
All told, about 11.5% of study participants had an oral HPV infection.
Overall, the prevalence of all high-risk and low-risk HPV types was consistently higher in men. High-risk HPV infections affected 7.3% of men overall and 1.4% of women overall, while the highest number of high-risk cases were found in the 50- to 54-year-old group for both men and women, the researchers found.
HPV 16, the most common type of high-risk HPV and known to contribute to head and neck cancers, was six times higher among men (1.8%) than women (0.3%). It was most prevalent in men 50 to 69 years old, the team said.
"The rates of oropharyngeal cancer among men have risen more than 300 percent in the past 40 years making oropharyngeal cancer most common HPV-related cancer in the United States," Deshmukh wrote in an email.
"In contrast, the rates of oropharyngeal cancer among women have declined."
Men who have had multiple sex partners, men who reported having sex with men, and men with genital HPV infections were found to have the highest rates of oral HPV, the study indicated.
HPV infections overall and high-risk HPV oral infections in particular were "significantly associated" with cigarette and marijuana use, the researchers found.
"Our study is also first to show that oral HPV infection prevalence was higher among Black men compared to White men (3% greater risk), those men who smoked more than 20 cigarettes daily compared to never smokers (10% greater risk), current marijuana users (6% greater risk), and men who have had more than 16 lifetime sexual partners (almost 20% greater risk)," Deshmukh wrote.
Eva McGhee, an assistant professor at the Charles R. Drew University of Medicine and Science, said the work of Deshmukh and his co-authors may raise awareness of the dangers of HPV.
McGhee, who was not involved in the new study, also published recent research on increasing HPV vaccination rates in an effort to eliminate the virus.
"A lot of people are not really familiar with how devastating oral cancer is in general," she said, and most are "not knowledgeable about how HPV infection can actually cause these awful cancers."
Meanwhile, she noted that "85% of the population will encounter" human papillomavirus in their lifetime. "Most people can clear the virus," she said, but those with compromised immune systems may find it difficult to naturally rid the virus from their bodies and therefore may develop a cancer associated with HPV.
"For cervical cancer, it takes at least 10 to 20 years for a cervical cancer to develop once infected" with HPV, McGhee said, noting that cancer develops slowly. Based on what she's been reading, "I'm actually thinking it's the same duration for oral cancer as well."
The authors "made it very clear that oral cancer is more prevalent among men," McGhee said.
"We cannot take this HPV infection lightly, because it does not discriminate. You can develop all of these types of cancers that's associated with HPV," McGhee said. "What's important is, we need to look at other types of preventative strategies or treatments for the older people."
Deshmukh also said better methods of screening are needed to prevent cancer among men who already have HPV or who are too old for the vaccine.
Even if all those eligible to receive the vaccine got it in the next year or so, "it will need at least 20-30 years to reverse the rising rates of oropharyngeal cancer among US men because majority of men at risk for this cancer are already older than vaccine eligibility age."
"We have methods to screen for cervical cancer; however, we still don't have ways to detect oropharyngeal precancer," Deshmukh said.