Prevalence of Human Papillomavirus Infection Differs for Men and Women

The age-specific prevalence of sexually transmitted human papillomavirus infection in women differs substantially from that in men who have sex with men, according to a new study published in the December 15 issue of The Journal of Infectious Diseases, now available online. The study, led by Peter V. Chin-Hong of the University of California, San Francisco, indicates a high prevalence of anal human papillomavirus (HPV) infection in all age groups of men who have sex with men. This finding contrasts with the age-related prevalence of cervical HPV infection.

Numerous studies have previously documented a causal link between HPV infection and anal and cervical cancers. Many studies have also shown that cervical HPV infection is strongly related to age, peaking early and falling after age 30. Little, however, is known about the age-specific prevalence of anal HPV infection in men who have sex with men. Most research on the subject has involved men in a narrow age range who were HIV-infected. The investigators described their study as the first to document anal HPV infection in a HIV-seronegative population of men who have sex with men who were diverse in terms of age and geography.

The study was conducted between January 2001 and October 2002 and involved 1,218 men who have sex with men living in Boston, Denver, New York, and San Francisco. The men were aged 18 to 89 years and 78% were white, 14% were Latino, 6% were African American, and 3% were Asian. The researchers found the prevalence rate of anal HPV infection to be 57%, and this rate did not change with age or from city to city. Factors associated with infection were receptive anal sex and having more than five sex partners in the previous six months.

Study results also described the nature of anal HPV infection in this group. Forty-five percent of those infected had more than one type of HPV. The prevalence of infection with “high-risk” HPV types associated with invasive anal cancer was 26%, suggesting that a high proportion of men who have sex with men may be at risk for anal cancer.

Chin-Hong and colleagues hypothesized that the sex-based difference in HPV epidemiology may reflect a difference between these populations in the number of new sex partners after age 30. They also suggest that there may be organ-specific and hormonal differences that contribute to the epidemiological differences. The investigators noted that one of the strengths of their study was its size and that it is the first multi-city study of anal HPV infection. A potential limitation, they explained, is that they do not know if their results can be generalized to certain subgroups of men who have sex with men, such as those living in rural areas.

“Based on the results of this study, previous assumptions about extrapolating data from cervical disease in women to anal HPV infection in men who have sex with men must be questioned,” Dr. Chin-Hong said. “The unique epidemiology of anal HPV infection should be further explored for its implications for HPV vaccine development and for understanding the risk factors of anal cancer.”