Background: The majority of anal cancer is associated with human papillomavirus (HPV) infection, yet little is known about women's risk of acquisition of anal HPV infection.
Methods: Risk factors for the acquisition of anal HPV infection were examined in a longitudinal cohort study of 431 women, via repeated measurement of HPV DNA.
Results: Seventy percent of women were positive for anal HPV infection at one or more clinic visits from baseline through a follow-up period that averaged 1.3 years. The incidence of a high-risk (HR) infection was 19.5 (95% confidence interval [CI], 16.0-23.6) per 1000 woman-months. The most common incident HR HPV types were HPV-53, -52 and -16. The presence of an HR anal HPV infection at baseline increased the risk of an incident anal infection by 65%. Baseline HR cervical HPV infection also predicted the acquisition of an HR anal HPV infection (odds ratio, 1.81 [95% CI, 1.09-3.02]). Nonviral risk factors for acquisition of HR HPV infection included younger age, lower socioeconomic status, greater lifetime number of sexual partners, past use of hormones, and condom use.
Conclusions: The results of this study suggest that women's risk of anal HPV infection is as common as their risk of cervical HPV infection.