Condom promotion to men will have more impact than discouraging `sugar daddies`, Zimbabwe study shows

Without better uptake of condoms among older men, the promotion of later sexual debut and discouragement of cross-generational sexual partnerships may do little to limit the spread of HIV in African countries, according to epidemiological modelling carried out by researchers from Imperial College, London.

Using data from an extensive study in Manicaland, Zimbabwe, Timothy Hallett and colleagues constructed a mathematical model to demonstrate the effect of different behavioural changes on HIV prevalence over time.

The original cross-sectional study interviewed around 10,000 men and women face-to-face in the rural province of Manicaland between 1998 and 2000, with a follow-up survey after three years. In three-quarters of interviews with literate respondents, the answers to sensitive questions about sexual behaviour were recorded using a confidential voting method.

The results were used as the basis for sexual behaviour frequencies in the model (for example, condom use at the last sexual act was reported by 17% of males and 8% of women). For the purposes of the model individuals in a hypothetical population were divided according to lower or higher sexual activity, and according to whether they formed partnerships with people with a similar level of sexual activity or not.

They were also divided according to whether they formed partnerships with people in a similar age group, or with people older or younger than themselves. Cross-generational partnerships were not rigidly defined in terms of age, and the age differences could be manipulated in the model.

Their simulations in the model showed that as the proportion of cross-generational partnerships rose above 10%, adult (15-49) HIV prevalence began to increase sharply, and if 40% of partnerships were cross-generational, HIV prevalence reached 15% and the ratio of female to male infections in the population reached 8:1.

The model also showed that if the proportion of cross-generational partnerships was reduced from 20% to 5% over 20 years, HIV prevalence in males aged 15-24 would fall slightly by year 20 (by 0.5%) but substantially among young women aged 15-24 (from 10% to 7% if replaced by partners of the same age, and from 10% to 5% if not replaced by new partners).

The lifetime risk of HIV infection was reduced by 10% for women and 5% for men if cross-generational partnerships were reduced and replaced by peer partnerships.

If cross-generational partnerships were eliminated and not replaced by peer partners (a partner reduction strategy, but note that cross-generational partnerships only account for a proportion of an individual’s partners), the lifetime risk of HIV infection would be reduced by 25% for women and 22% for men.

In comparison delaying sexual debut by two years had a modest effect, resulting in a reduction in lifetime risk of around 8%.

“Although abstinence undeniably reduces the risk of infection, its impact on the spread of HIV and the average chance of infection over a lifetime is small,” the authors say.

However, the intervention that had the greatest impact was increasing condom use in older men (over 25 years) to the levels reported by 15-24 year old males. This resulted in a 20% reduction in the lifetime risk of infection for both men and women. In comparison, doubling condom use across the whole population would have a lesser impact for women, resulting in a 15% reduction in the lifetime risk of infection.

“The real impact of cross-generational sex on the population-level spread of HIV is the power imbalance in those partnerships and the implications this has for the chance that condoms will be used,” the authors conclude.

In sub-Saharan Africa much concern has been expressed about the epidemiological effect of cross-generational sexual relationships. In particular, women involved in HIV prevention in some countries have argued for a need to target `sugar daddies`: men who are older, have more money and who seek sex with younger women.

At the recent South African AIDS Conference Dr Olive Shisana of the South African Human Sciences Research Council told the conference that the three Cs - cars, cash and cellphones - were the currency traded during cross-generational relationships in South Africa, and other researchers agree that corss-generational sex needs to be seen as an econcomic survival strategy for young women.

But the Imperial College researchers say their results show that specific targeting of cross-generational sex will not produce the desired impact on HIV prevalence.

“Our results show that behaviour change interventions should aim to minimise unprotected sexual contact by young women with anyone and should not target the age difference between sexual partners per se…interventions should not be narrowly targeted at particular at-risk groups but instead should tackle risky behaviour throughout the sexual network.”