Among the victims of the HIV epidemic, women have historically been neglected. Even with widespread recognition of this problem, risk behaviors among women are still poorly understood -- and that's especially true when it comes to anal sex.
At the recent HIV Research for Prevention conference in Chicago, Illinois, Jocelyn Elmes, Ph.D., from Imperial College London presented results of her research on low-income women across 20 U.S. cities. She found that a staggering 38 percent of HIV infections among these women may be due to anal intercourse and noted that risk factors among women merit further study.
The risk of HIV transmission from anal sex among men who have sex with men is well established, and recognition of the risk factors has allowed doctors and public health workers to reach out to the community with preventative messaging around condoms and pre-exposure prophylaxis, or PrEP, Elmes said during the presentation.
Yet, for women, who can contract HIV through vaginal or anal intercourse, the relative risk factors are not well known, which may lead to a disconnect in prevention efforts. During her presentation, Elmes said that her research demonstrated the need for improved messaging about condom use during vaginal and anal sex among the low-income cohort she studied. Elmes also suggested that this group might benefit from PrEP moving forward.
This research underscores the importance of engaging women in open conversations about their sexual practices, including anal sex, to ensure they can meet their prevention needs, said Jessica Terlikowski, director of prevention technology education at AIDS Foundation of Chicago.
"I think we are just beginning to put together a picture of anal sex behavior at the epidemiological level in women, but very little of specific behaviors and biology of rectal transmission," said Craig W. Hendrix, M.D., director, Division of Clinical Pharmacology at Johns Hopkins University.
To better understand anal sex practices among heterosexual women, Elmes and her colleagues reviewed survey data from two data sets from the Centers for Disease Control and Prevention (CDC)'s National HIV Behavioral Surveillance (NHBS) from 2010 and 2013.
The data included survey responses from more than 9,000 low-income women living in 20 cities in the United States. The respondents were mostly black, and their average age was 37. Elmes excluded injection drug users from her analysis.
The first step in the research was to get a better sense of women's sex practices. Overall, the survey data revealed that one in three women reported anal intercourse in the past year, and that figure was higher among women who said they had exchanged sex for money. The women who practiced anal intercourse also had other high-risk behaviors, Elmes said. They reported three times as many annual partners and were more likely to say that their last sexual encounter was with a casual partner. Worryingly, women were 60% less likely to report using condoms the last time they had anal sex rather than vaginal sex.
Second, Elmes' analytical methods sought to understand the relative contribution of anal intercourse to HIV infections, taking into account factors such as regional HIV prevalence and whether women were on treatment.
Using these parameters, she and her colleagues calculated the increased likelihood of HIV infection due to anal intercourse and found that 38 percent of HIV infections may have been due to anal intercourse. That estimate was fairly consistent across races and age groups, but women who reported exchanging money for sex had a higher percent of HIV infection possibly caused by anal intercourse.
In addition, estimates varied from city to city. Denver had the lowest rate, at 20 percent of estimated HIV infections due to anal intercourse, and San Juan had the highest rate at 44 percent.
Elmes noted that one of the bigger limitations on her meta-analysis was that the relative risk of anal to vaginal intercourse is uncertain. This is because the literature is split on this issue, with different studies coming to widely different conclusions. For example, a 2010 study found that the risk of contracting HIV during anal intercourse might be around 18 times greater than during vaginal intercourse. Yet other estimates are far lower, and the CDC estimates the risk to be about 12 percent greater.
"Anal intercourse practice among low-income women is common, and condom use is low," Elmes said during the presentation. Therefore, low-income women would benefit from additional efforts to encourage condom use as a method of prevention, with a specific focus on condom use for anal sex, she said. Importantly, Elmes raised the possibility that low-income women are an overlooked population who might benefit from PrEP.
"It seems reasonable to assume that whatever works for anal sex prevention in men who have sex with men will work as well in women," Hendrix said, noting that any intervention to protect from anal HIV transmission needs to be developed and confirmed in both men and women.
Terlikowski went further, saying that this research should demonstrate an urgent need to advocate for PrEP use among women.
"Women who are engaging in condomless anal sex are strong candidates for PrEP and must be told about it so they can take control of their health and reduce their risk of acquiring HIV," she said.