Age-disparate sexual partnerships - it’s more complicated than sugar daddies and blessers

Sugar daddies and blessers are men who provide gifts, money or other benefits to much younger women in exchange for sex.  These relationships are inevitably complex and are often seen as an important mode of transmission for HIV, particularly in Southern and East Africa.  Health education campaigns have raised the issue and aimed to discourage young women from having sex with older men.  However, the research on age-disparate relationships has been harder to interpret. Some studies show that having older partners is not necessarily an independent risk factor for HIV acquisition and others demonstrate a clear age difference in some couples where phylogenetics makes transmission seem very likely.  Nor do all age-disparate relationships involve sugar daddies or blessers.  Many women choose partners who are a few years older than themselves without such clear cut transactional motives.

This month saw Akulian et al. conclude that “age of sexual partner is a major risk factor for HIV acquisition” with frighteningly high rates of HIV incidence of 9.7 per 100 person years occurring among women aged 15-24 years old reporting partnerships with men aged 30-34 years old.  Yet the same research group (Harling et al.), in the same geographic community three years ago, concluded that “partner age disparity did not predict HIV acquisition” and cautioned against using resources for public health campaigns to reduce such partnerships.  A recent paper (de Oliveira et al.) from another research setting, also in KwaZulu-Natal, used phylogenetics to link isolates that were likely to be transmission pairs.  They too found that younger women (aged younger than 25 years) were more likely to have older male partners.  On average in the couples linked by phylogenetics the age difference was 8.7 years when the woman was younger than 25 but only 1.1 years when she was older than 25 years.

This month Schaefer et al. also demonstrated that in the Manicaland cohort in Zimbabwe, where incidence is somewhat lower than in KwaZulu-Natal, young women aged 15-24 years in partnerships with older men were likely to become  HIV positive .  They note that even the introduction of ART has not changed this observed finding, suggesting that the failure to reach men as effectively as we are reaching women, may be a significant reason for ongoing transmission.

The Akullian et al. paper used statistical techniques to smooth the observations from more than 1000 seroconversions observed in more than 25 000 person years of follow-up.  Harling et al. followed the cohort of women aged 15-29 years in the study area and observed 458 seroconversions over 5913 woman years of observation.  Although age-disparate relationships were common, age disparity was not an independent risk factor for HIV infection.  Akullian et al. explain that the real risk is from men aged 30-34 years.  Men in this age group are more likely to have recently acquired HIV, as it is the peak age group for incidence in males.  They are therefore likely to be particularly infectious with higher viral loads. They are also a group that has a low uptake of HIV testing and linkage to ART. 

The rates of ART use and HIV prevalence of older male partners for young women was explored by Evans et al. using data from the South African 2012 National HIV survey.  They found that male partners who were considerably older were more likely to be taking ART and so were likely to transmit fewer infections to their partners, which would tie in well with the Akullian et al. hypothesis of the highest risk being men aged 30-34 years.  The highest incidence is among young women, and these women are most likely to have partners in the 30-34 year old age band.  So we must be careful not to over-generalize.  This helps to explain the apparently differing results from these various studies.  If all age-disparate relationships are included in epidemiological studies, the important impact of transmission from recently infected and untreated 30-34 year old men to their younger female partners aged younger than 25 years may be diluted.

All these studies come from South Africa (usually KwaZulu-Natal) and Zimbabwe and so further detailed epidemiology supported by phylogenetics would be welcome from elsewhere.  Nonetheless, these various studies do translate into a clear message for action.  We need to work hard to find better ways to engage men aged 30-34 years, encourage them to get tested for HIV (see the HIV self-testing approaches above for instance) and link them to care and effective treatment much more efficiently than we are doing at present. 

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