Your age could affect your ability to fight off this nasty virus.

Sexually transmitted diseases are often thought of as a young person’s problem—15- to-24-year-olds do make up half of all new cases—but some may be more dangerous the greyer you get.Older men who catch a certain type of human papillomavirus (HPV) may be less able to clear it from their bodies, researchers from the Moffitt Cancer Center found.According to the study, men 45 and older were significantly more likely to have infection of oral HPV16—the type that often shows no symptoms and has been implicated as a cause of head and neck cancers—persist for longer than a year in their mouths than men in younger age groups were.And that’s important, because HPV viruses that stick around in the body are more likely to drive the development of some cancers, says study author Christine Pierce Campbell. The researchers aren’t exactly sure how long oral HPV16 needs to circulate in the mouth to raise the risk of men’s head and neck cancers, but they believe it’s similar to the 2-year figure that spikes women’s risk of HPV-caused cervical cancer.

So why might older guys be at a greater danger? It may be due to the natural declines in immune function as we age that leave us unable to successfully clear the virus from our bodies.

“You aren’t able to fight off infection as well as when you were younger,” says Pierce Campbell. “And we know that HPV infection really flourishes in an environment where there is little immune response.”

Oral HPV infection is rare, so the researchers aren’t certain how it spreads. But experts believe it may be from performing oral sex on partners who have the infection in their genitals. Or guys may be able to pick it up as a genital infection and then transfer it to their oral cavities through hand-to-mouth contact.

More research is needed to confirm the link—and to study how likely transmission is to occur sexually. In the meantime, the best way to avoid picking up the virus is getting the HPV vaccine.

Researchers from NYU Langone Medical Center found that more than two-thirds of adults have been infected with at least one kind of HPV. But the vaccine, a series of three injections, protects you from four strains of HPV that cause genital warts and cancer of the anus, mouth/throat, and penis. In fact, the treatment could cut your risk of genital warts by up to 90 percent, says a study inNew England Journal of Medicine.

Even though research isn’t clear on sexual transmission for oral HPV, you should always make sure to practice safe sex—that means condoms for intercourse and oral sex—if you’re worried about picking up any kind of STD.

Words by Christa Sgobba and Ali Eaves. Image from Thinkstock.