Issue 3 / 30 January 2012

ORAL human papillomavirus (HPV) infection is significantly more common in men than women and increases with sexual experience, according to one of the first population-based studies of the oral infection.

The study, published in JAMA, involved 5579 people aged 14 to 69 years who provided a 30-second oral rinse for detection of HPV DNA as well as information about their sexual history and substance use. (1)

The overall prevalence of oral HPV infection, which is associated with oropharyngeal squamous cell carcinomas, was 6.9%. Men had a significantly higher prevalence of infection of 10.1% compared to only 3.6% for women.

The overall prevalence of HPV type 16, associated with at least 90% of HPV-positive oropharyngeal squamous cell carcinomas, was 1%.

The researchers said only about 16% of the gender difference could be explained by sexual behaviour, even though men had a higher number of sexual partners than women on average.

Infection increased with the number of sexual partners. Among people who had more than 20 lifetime sexual partners, the oral HPV infection rate was 20.5%.

“Our data provide evidence that oral HPV infection is predominantly sexually transmitted”, the researchers wrote.

Oral sex was not singled out as a particular risk factor in this study.

“[T]he colinearity of sexual behaviors precluded associating infection with any particular behaviors”, the researchers wrote.

Current smoking and intensity of smoking were independently associated with oral HPV infection, particularly among women.

The peak ages for oral HPV infection were 30–34 years and 60–64 years. This bimodal age pattern was particularly striking among men, but again researchers could not pinpoint the precise reason for this.

The researchers said efficacy of HPV vaccination against oral infection was unknown, but called for more research in this area.

“Given an analysis of US cancer registry data recently projected that the number of HPV-positive oropharyngeal cancers diagnosed each year will surpass that of invasive cervical cancers by the year 2020, perhaps such vaccine trials are warranted”, they wrote.

In Australia, HPV vaccination is government funded for girls in the first year of secondary school, and the Pharmaceutical Benefits Advisory Committee recently recommended extending the program to boys aged 12–13 years.

A related editorial in JAMA said that HPV-positive oropharyngeal tumours were increasing in incidence, now exceeding the number of these tumours caused by tobacco and alcohol abuse. (2)

However, the editorial said the pathogenesis of oropharyngeal cancer was unclear.

“Future research will need to identify the natural history of HPV-related oropharyngeal dysplastic lesions and evaluate potential screening methods to detect oropharyngeal dysplasia prior to invasion.”

The editorial also noted that the rate of HPV infection of the mouth was much lower than at other sites. For instance, the prevalence of cervicovaginal HPV was 42% in women aged 14–59 years in one study, and anal HPV prevalence ranged from 42% to 57% among homosexual men.

This prompted questions of whether the oral cavity was relatively resistant to infection, or was better able to clear infection, the editorial said.

– Sophie McNamara

1. JAMA 2012; 26 January (online)
2. JAMA 2012; 26 January (online)

Posted 30 January 2012

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