Background:
More than one-third of women in the US have engaged in heterosexual anal intercourse (HAI). The risk of acquiring HIV per sexual act is estimated to be 18 times higher for receptive anal intercourse than receptive vaginal intercourse; HAI is also associated with lower rates of condom use. Little is known regarding HAI frequency, condom use, motivations for HAI, including as a method of contraception, and perceptions of HIV risk.
Objectives
This multi-phase study was designed to achieve several goals. The first goal was to determine the prevalence and frequency of HAI and condom use with HAI among US women and men. The second goal was to describe the relative frequency of motivations for HAI, and to correlate condom use with motivations for HAI and knowledge of HIV/STI risks among US women and men. The third goal was to explore perspectives and motivations related to HAI in a subsequent qualitative study among Seattle women who engage in HAI.
Methods
We first conducted a national representative sexual behavior survey of over five thousand women and men ages 15 to 19 years old. The sample size needed was based on a primary outcome of condom use with HAI and a primary predictor of motivation for HAI. The survey was fielded by GfK KnowledgePanel, which provided nationally representative sampling through a panel recruited by address-based sampling.
We conducted a subsequent qualitative study through in-depth interviews using a semi-structured interview guide. The interview guide was developed utilizing a conceptual framework based on the Theory of Planned Behavior. All interviews were conducted in-person with one of two female researchers. Participants included twenty women ages 18 to 50 years old who had engaged in HAI within the past three months. Both the quantitative and qualitative study components were approved by the University of Washington Institutional Review Board (IRB).
Results
Thirty-seven percent of women in the US have engaged in HAI at least once. In the past three months, twelve percent have engaged in HAI, compared to eighty-three percent reporting vaginal intercourse in the same time period. The most common motivations for HAI were self and partner pleasure and curiosity. Twice as many men as women reported ever using HAI as a method of contraception (13.5% versus 6.6%). Condom use was lower for anal versus vaginal intercourse (9% versus 16%). More than 70% of adults erroneously believe that HIV risk is greater for vaginal intercourse than anal intercourse.
The qualitative study revealed that women’s intent to engage in HAI is influenced by their attitudes towards HAI and level of control and trust with their partners.  Primary motivators are partner and personal pleasure and sexual curiosity and experimentation.  Most women perceive of negative societal norms towards HAI. While this does not appear to affect intention to engage in HAI, it does affect disclosure of this sexual activity with friends and healthcare providers.
Conclusions
HAI is common in the US. Both women and men report a wide range of motivations for both HAI and condom use with HAI. Among adults who engage in HAI, 10% have used this as a method to prevent pregnancy at least once. Significant knowledge gaps still exist regarding HAI and HIV transmission. Many women do not feel comfortable disclosing this sexual behavior to others, including healthcare providers, due to perceived negative societal normative beliefs regarding HAI.