Methods

Participants

Participants were recruited from urban townships (N  =  3051, 69%) and an urban STI clinic (N  =  1360, 31%) in Cape Town. Cape Town is a racially diverse city of 3.2 million people; 31% black/African, 48% coloured (mixed race), 19% white and 2% Indian/Asian. The township communities that participated are located within 20 km of Cape Town’s central business district. One township is nearly exclusively populated by bBlack South Africans of Xhosa cultural heritage and the other was historically populated by coloured individuals during the apartheid era and is among the first townships to integrate racially in Cape Town, with large numbers of indigenous Africans moving into the township. We also collected data from an STI clinic located in Cape Town that treats over 1800 patients each month. Approximately half of all patients seen at the clinic have previously received STI diagnostic and treatment services.

Measures

Surveys were administered in English, Xhosa (an indigenous African language) and Afrikaans (a former South African national languages rooted in Dutch). All measures were translated using back translation procedures. The survey included demographic and HIV risk history characteristics, substance use and sexual behaviours.

Demographic and HIV risk history characteristics

Participants reported their age, race, years of formal education, whether they were employed and their marital status. To assess HIV risk history, participants were asked if they had ever used condoms in their lifetime, whether they had ever exchanged sex for money, a place to stay, or material goods and their lifetime history of STI diagnoses. Participants also reported whether they had ever been tested for HIV and if they had been tested, they were asked their most recent HIV test result. Participants indicated whether they had used alcohol, cannabis (dagga) and other drugs in the previous 3 months.

Sexual behaviours

Participants reported their number of male and female sex partners and frequency of sexual acts, including vaginal and anal intercourse with and without condoms in the previous 3 months. Participants were instructed to think back over the past 90 days (3 months) and estimate the number of male and female sex partners they had had and the number of occasions in which they practised vaginal and anal sexual behaviours with and without condoms. These measures are similar to others that have been found reliable and valid in previous research.12 We calculated the proportion of intercourse occasions protected by condoms separately for vaginal and anal intercourse (protected acts/total acts). We also computed the proportion of all sexual intercourse occasions accounted for by anal intercourse (anal intercourse/total intercourse).

Sampling procedure

Data were collected using time and place sampling procedures in two townships and a major STI clinic in Cape Town. The township samples were obtained through venue-based survey procedures. In each township men and women aged 18 years and older were approached while in public places and asked to complete a brief anonymous survey. Field workers were instructed to approach the next person they saw as their participants completed surveys. The 37 venues sampled across the two townships included day hospitals (12% of community surveys), shopping areas (21%), community centres (25%), taxi waiting areas (18%) and street junctions that included bus stops, waiting areas and street vendors (24%). These venues were purposely selected because they represent public access sites throughout the townships and their surrounding areas. Questionnaires were administered by teams of field workers recruited from the townships and trained in survey collection, the study protocol and research ethics, particularly focusing on confidentiality. Sampling occurred throughout hours of the day and days of the week. Participants were approached by a field worker and asked whether they would answer an anonymous questionnaire. More than 90% of persons approached agreed to complete surveys.

Participants in the STI clinic sample were recruited to complete anonymous surveys of sexual behaviour and health at a Cape Town public health clinic. Potential participants were referred to the study recruiter by their doctor or nurse following their STI diagnostic and treatment services; 91% of patients referred to the study agreed to complete surveys. All STI patients were referred to the study. Sampling occurred during all hours of clinic operation. The community and clinic anonymous surveys were collected between 2003 and 2006. Ninety-five per cent of persons who agreed to complete the survey self-administered the measures with minimal assistance and 5% required that the survey be read to them. When assisting participants, field workers read the survey items to participants who completed their own responses on their survey. All participants received 15 South African Rand (US$3) to compensate for their time. All of the study procedures were approved by the University of Connecticut and Human Sciences Research Council institutional review boards.

Data analyses

We conducted analyses on three partitions of the data to examine rates of sexual behaviour and related factors. First, we compared the township and clinic patient samples on sexual partners, sexual behaviours and condom use. Second, we tested for differences between participants who engaged in heterosexual anal intercourse in the previous 3 months with those who did not report heterosexual anal sex on all demographic, HIV risk history, substance use and sexual behaviours. Finally, we examined sexual partners and sexual behaviours of men and women who had engaged in heterosexual anal sex in the previous 3 months. All comparisons were conducted using logistic regressions. We report odds ratios, significance values and 95% CI. Because of the large sample size and exploratory nature of this study, statistical significance was defined at the conservative level of p<0.01.

Results

Among the 2769 men surveyed, 176 (6%) reported same-sex partners in the previous 3 months, of which 51% had engaged in anal intercourse. To avoid confounding heterosexual anal intercourse with same-sex anal intercourse we omitted the 176 men who had had sex with men from further analyses. The final sample consisted of 2593 men and 1818 women who reported a total of 3859 and 2655 opposite sex partners in the past 3 months, respectively. The median age of participants was 30 years; 64% of participants were black/African and 32% self-identified as coloured or mixed race; 43% were currently working and 32% were married or living with a sex partner. A total of 360 (14%) men and 172 (10%) women reported anal intercourse in the previous 3 months; 44% of participants who engaged in anal sex did so for less than half of all intercourse occasions, 28% engaged in anal intercourse half the time and the remaining 28% engaged in anal intercourse more than half of the time, with 9% (N  =  45) reporting exclusively engaging in anal intercourse.

Table 1 shows the demographic, substance use and sexual behaviours of participants sampled in the township communities and the STI clinic. Categorical variables are shown in the upper panel and continuous variables are shown in the lower panel of the table. The two samples differed along several demographic and risk history characteristics. As expected, STI clinic patients reported significantly more sex partners and frequencies of sexual behaviours in the previous 3 months compared with community members, with the only exception being the proportion of anal intercourse occasions protected by condoms—for which groups did not differ.

Factors associated with engaging in heterosexual anal sex

Table 2 presents the characteristics and behaviours of the sample partitioned by whether participants had engaged in anal intercourse in the past 3 months. Controlling for sampling venues, results showed that individuals who practised heterosexual anal sex were significantly younger, less likely to be married or living with a sex partner and more likely to have had a lifetime history of condom use compared with those who did not engage in anal sex. In addition, individuals who practised anal intercourse were significantly more likely to report a history of all HIV risk factors, including a history of STI and a history of sexual exchange, and were more likely to report alcohol and other substance use in the previous 3 months. Participants who practised anal sex were also more likely to have been tested for HIV and were more likely to have tested HIV positive (see table 2). In terms of other sexual behaviours, individuals who engaged in anal intercourse reported more sex partners than persons who did not engage in this behaviour. Practising anal sex was significantly associated with engaging in less unprotected vaginal intercourse and greater vaginal intercourse protected by condoms.

Gender differences among persons who practised anal intercourse

Sexual behaviour differences reported by men and women who engaged in anal sex are shown in table 3. Men who engaged in anal intercourse reported more sex partners than women and men also reported greater condom use during vaginal and anal intercourse. Finally, men engaged in proportionally more anal sex relative to vaginal sex than did women.

Discussion

The current study is among the first to examine heterosexual anal intercourse practices in South Africa. The results are consistent with previous research, showing that anal intercourse is practised at relatively low rates among heterosexual men and women.10 Less than 15% of men and women practise anal sex and even among those who do engage in anal intercourse, most do so at significantly lower rates than vaginal intercourse. Condom use during anal intercourse mirrored the rates of condom use for vaginal intercourse, and we observed only small differences between community and STI clinic samples in their anal intercourse practices. Engaging in anal intercourse was associated with several common factors for sexual transmission risks of HIV in general, including sexual exchange and substance use. In addition, we found that people who practised anal sex were more likely to have had an STI diagnosis, were more likely to have been tested for HIV and were more likely to have tested HIV positive. Participants who engaged in anal sex were also more likely to have used condoms in their lifetime and were using condoms at a similar rate for anal and vaginal intercourse at the time of the study. Given these and other findings,10 11 the HIV epidemic in South Africa cannot be attributed to anal intercourse as some commentators have suggested.13 Of course, the precise role anal intercourse has played in the history of South Africa’s HIV epidemic is unknown. Nevertheless, our data parallel other research showing that anal intercourse should neither be the focus of nor be ignored by HIV prevention interventions in South Africa.

The current findings should be interpreted in light of the study methodological limitations. Our study concentrated on self-reports of sexual practices and substance use as well as HIV risk history factors. These behaviours are private and several are socially stigmatised and therefore subject to underreporting. We cannot rule out the possibility that some men did not report same-sex relationships and were included in the sample. It is also possible that participants confused the meaning of vaginal and anal sex, mistakenly reporting or not reporting the occurrence of anal sex. For example, it is possible that some participants mistakenly reported rear-entry vaginal intercourse as anal intercourse and vice versa. We also relied on a retrospective recall period of 3 months which can result in inaccurate estimates of higher frequency behaviours.12 The current study measures did not ask about motivations for practising anal intercourse, such as to maintain vaginal virginity or to avoid pregnancy. Our samples were also drawn by convenience and cannot be considered representative of Cape Town communities. Finally, our study requires replication and confirmation before drawing firm conclusions. Despite these limitations, we believe that our findings have important implications for HIV prevention in South Africa.

Behavioural interventions aimed towards heterosexual populations in South Africa should include anal intercourse among their target behaviours for HIV transmission risk reduction. Relative to vaginal intercourse, anal intercourse probably accounts for a small number of Africa’s HIV infections. However, ignoring even low rates of this highly efficient means of HIV transmission in a generalised HIV epidemic would be remiss. Including anal intercourse as a target behaviour for interventions should not, however, detract from the importance of reducing risks from vaginal intercourse. Recognising anal intercourse practices in HIV prevention also calls attention to examining the potential efficacy of anal/rectal microbicides.14 Risk-reduction counsellors and health educators may require sensitivity training to increase their openness to discussing anal sex with their clients. In addition, interventions that emphasise skills training, such as condom use skills and sexual communications skills, should include both anal and vaginal intercourse risk reduction. Comprehensive HIV risk-reduction strategies that include reducing HIV transmission risks incurred during anal intercourse are urgently needed in South Africa.