The association between heterosexual anal intercourse and HIV infection is not well studied, despite the understanding that anal intercourse is a high-risk behavior [1–3]. No study has assessed the prevalence of heterosexual anal intercourse and its association with HIV infection in a sub-Saharan African population, largely as a result of the belief that anal sex is not widely practised in this region . In a high-prevalence epidemic in which heterosexual intercourse is presumed to be the primary route of HIV infection, such as exists in sub-Saharan Africa, it is possible that epidemiological studies and HIV prevention programmes are overlooking a potentially significant pathway of HIV transmission. Studies of heterosexual anal sex in other populations have determined that heterosexual individuals are less likely to use condoms for anal sex than for vaginal sex, and are less likely than men who have sex with men to use condoms for anal sex . In the absence of any specific evidence, it seems reasonable to assume that Africans who engage in heterosexual anal intercourse would be similarly disinclined to use condoms.
The South African National Youth Survey (NYS), conducted by the Reproductive Health and HIV Research Unit at the University of the Witwatersrand, Johannesburg, provided an opportunity to estimate the prevalence of anal intercourse among South African youth and explore its association with HIV infection in this population. The NYS was a nationally representative household survey of 11 904 South Africans aged 15–24 years, conducted between March and August 2003. Participants answered survey questions about sexual risk behaviors, attitudes and norms around HIV/AIDS, and the awareness of and exposure to loveLife, a national youth HIV prevention campaign. Survey participants provided an oral fluid sample for HIV testing. All results were adjusted for the survey sampling design. HIV prevalence in this age group was 10.2% (5.2% for men, 15.5% for women). Prevalence among 15–19 year olds (2.5% for men, 7.3% for women) was lower than among 20–24 year olds (7.6% for men, 24.5% for women). Full results of the NYS have been reported elsewhere .
The prevalence of anal intercourse in this sample was 3.6% among both men and women. Sexually experienced youth accounted for 67% of the entire sample. Among sexually experienced youth, 5.5% of men and 5.3% of women reported ever engaging in anal intercourse. Only 0.06% of men reported other men as sexual partners; we therefore presume that we are describing heterosexual anal intercourse with men as insertive partners and women as receptive partners.
Participants were asked separate questions about their experience of vaginal and anal intercourse. Survey questions regarding the frequency of condom use did not treat these as separate categories; participants were reminded only that ‘sex is defined as vaginal or anal intercourse’. Therefore, there was no way to determine the frequency of condom use specifically for anal intercourse.
In unadjusted analyses, women reporting anal intercourse were not significantly more likely to be HIV infected than those reporting only vaginal intercourse [odds ratio (OR) 1.2, 95% confidence interval (CI) 0.7–2.0]. However, young men reporting anal intercourse were two times more likely to be HIV infected than those reporting only vaginal intercourse (OR 2.0, 95% CI 1.1–3.6). We explored the potentially confounding effects of age and other sexual risk behavior variables on anal intercourse. Among all sexually experienced young men, those who reported anal sex were significantly more likely to be older than 20 years of age, to have had more than four lifetime sexual partners, and to have engaged in sexual intercourse while under the influence of alcohol or other drugs (Table 1). Variables with associations of P > 0.15 were included with anal intercourse as independent variables in a multivariate model with HIV infection as the outcome, and multiple logistic regression was performed using Stata 7.0 (Stata Corporation, College Station, Texas, USA). The adjusted risk of HIV infection from anal intercourse was of borderline significance (OR 1.7, 95% CI 1.0–3.0).
The increased risk of HIV infection among young men reporting anal intercourse was more pronounced among sexually experienced men aged 15–19 years. In this group, reporting anal intercourse was associated with more than four lifetime sexual partners, sexual intercourse under the influence of alcohol or drugs, and transactional sex. After controlling for associated risk behaviors, men in this age group reporting anal sex were more than four times more likely to be HIV infected than those reporting only vaginal sex (OR 4.3, 95% CI 1.5–12.1). Because anal intercourse is likely to be an underreported activity, the real risk may in fact be higher than these data indicate.
These findings have important implications for current HIV prevention programmes and for future research. Programmes that promote behavior change among youth through abstinence, partner reduction, and condom use do not specifically address the HIV risk associated with anal intercourse. It is possible that in the absence of specific information, youth may erroneously view anal intercourse as less risky than vaginal intercourse, and therefore may not be inclined to use condoms. The youngest and most sexually active youth appear to be most vulnerable. Anal intercourse may also provide an alternative sexual outlet for youth who choose abstinence from vaginal sex as a contraceptive or HIV risk reduction strategy, and these youth may be similarly disinclined to use condoms.
We recommend that current interventions to reduce HIV risk among youth should directly address the HIV risk associated with anal intercourse, and encourage condom use and condom-safe lubrication for this sexual activity. Research should be initiated in South Africa to explore current perceptions of the safety of anal intercourse among youth populations. Future behavioral and epidemiological research throughout sub-Saharan Africa should begin to assess separately the frequency of vaginal and anal intercourse, and the frequency of condom use for each sexual behavior.
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