For the study, the researchers reviewed data from the National Nutrition Examination Survey on 13,089 people aged 20 to 69, and calculated the number of people who had oral HPV infections.
In the latest study, published in the journal Annals of Oncology, experts analysed data from 13,089 people aged 20-69 who had been tested for oral HPV infection and used the numbers of oropharyngeal cancer cases and deaths from USA registries to predict their risk of cancer.
The researchers say one of the purposes of the study was to determine whether it would be worthwhile to screen an entire population of patients for oropharyngeal cancer risk.
Only 0.7 per cent of men will develop oropharyngeal cancer - cancer of the middle part of the throat - during their lifetimes.
Smoking cigarettes, along with having five or more oral sex partners, increases men's risk for the most common type of head and neck cancer. Oral infections with the dozen HPV types known to cause oropharyngeal cancer (especially HPV 16, the type that causes most throat cancers) were present at low prevalence in every defined group in the study, the researchers found. Women ages 20 to 69, for example, had a frequency of infection of just over 1 percent, compared to 6 percent for men ages 20 to 69. According to the National Cancer Institute, 70 percent of oropharyngeal cancers are caused by HPV type 16 infection, a high-risk strain of the virus. Men ages 50 to 59 were most likely to have an infection (8.1 percent) of any age group. Through samples of mouthwash that detected HPV cells, the researchers were able to ascertain the prevalence of oral HPV infections. But it turns out that when a man also smokes the risk is even higher. Prevalence was 14.9% among men who smoked and reported five or more lifetime oral sex partners, compared to less than half that (7.3 percent) for men who reported five or more lifetime oral sexual partners but did not smoke.
Smoking also was associated with higher oral HPV prevalence.
It was found women who had one or no oral sex partners during their lifetimes had the lowest prevalence of oral infection with cancer-causing types of HPV, with 1.8 per cent of smokers infected, and 0.5 per cent of non-smokers.
Infection with any potentially cancer-causing HPV type is not as predictive of cancer risk as it may seem, the researchers note.
Doctors hope that proof of the increased risk caused by the two behaviours helps identify the people who are more at risk of developing head and neck cancer. "It is a rare cancer and for most healthy people the harms of screening for it would outweigh the benefits because of the problem of false positive test results and consequent anxiety", said co-author Carole Fakhry, associate professor at the Johns Hopkins Department of Otolaryngology.
Now there are no tests that can be used for screening people for oropharyngeal cancer.
The new study's findings suggest it is crucial for boys to get the HPV vaccine.