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

Editor’s notes: 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 25-34 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 25-34 years.  The highest incidence is among young women, and these women are most likely to have partners in the 25-34 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 25-34 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 25-34 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. 

Sexual partnership age pairings and risk of HIV acquisition in rural South Africa.

Akullian A, Bershteyn A, Klein D, Vandormael A, Bärnighausen T, Tanser F. AIDS. 2017 Jul 31;31(12):1755-1764. doi: 10.1097/QAD.0000000000001553.

Objective: To quantify the contribution of specific sexual partner age groups to the risk of HIV acquisition in men and women in a hyperendemic region of South Africa.

Design: We conducted a population-based cohort study among women (15-49 years of age) and men (15-55 years of age) between 2004 and 2015 in KwaZulu-Natal, South Africa.

Methods: Generalized additive models were used to estimate smoothed HIV incidence rates across partnership age pairings in men and women. Cox proportional hazards regression was used to estimate the relative risk of HIV acquisition by partner age group.

Results: A total of 882 HIV seroconversions were observed in 15  935 person-years for women, incidence rate = 5.5 per 100 person-years [95% confidence interval (CI), 5.2-5.9] and 270 HIV seroconversions were observed in 9372 person-years for men, incidence rate = 2.9 per 100 person-years (95% CI, 2.6-3.2). HIV incidence was highest among 15-24-year-old women reporting partnerships with 30-34-year-old men, incidence rate = 9.7 per 100 person-years (95% CI, 7.2-13.1). Risk of HIV acquisition in women was associated with male partners aged 25-29 years (adjusted hazard ratio; aHR = 1.44, 95% CI, 1.02-2.04) and 30-34 years (aHR = 1.50, 95% CI, 1.08-2.09) relative to male partners aged 35 and above. Risk of HIV acquisition in men was associated with 25-29-year-old (aHR = 1.72, 95% CI, 1.02-2.90) and 30-34-year-old women (aHR = 2.12, 95% CI, 1.03-4.39) compared to partnerships with women aged 15-19 years.

Conclusion: Age of sexual partner is a major risk factor for HIV acquisition in both men and women, independent of one's own age. Partner age pairings play a critical role in driving the cycle of HIV transmission.

Abstract [1]Full-text [free] access [2]

 

Do age-disparate relationships drive HIV incidence in young women? Evidence from a population cohort in rural KwaZulu-Natal, South Africa.

Harling G, Newell ML, Tanser F, Kawachi I, Subramanian SV, Bärnighausen T.J Acquir Immune Defic Syndr. 2014 Aug 1;66(4):443-51. doi: 10.1097/QAI.0000000000000198.

Background: Based on ethnographic investigations and mathematical models, older sexual partners are often considered a major risk factor for HIV for young women in sub-Saharan Africa. Numerous public health campaigns have been conducted to discourage young women from relationships with older men. However, longitudinal evidence relating sex partner age disparity to HIV acquisition in women is limited.

Methods: Using data from a population-based open cohort in rural KwaZulu-Natal, South Africa, we studied 15- to 29-year-old women who were HIV seronegative at first interview between January 2003 and June 2012 (n = 2444). We conducted proportional hazards analysis to establish whether the age disparity of women's most recent sexual partner, updated at each surveillance round, was associated with subsequent HIV acquisition.

Results: A total of 458 HIV seroconversions occurred over 5913 person-years of follow-up (incidence rate: 7.75 per 100 person-years). Age disparate relationships were common in this cohort; 37.7% of women reported a partner 5 or more years older than themselves. The age disparity of women's partners was not associated with HIV acquisition when measured either continuously [hazard ratio (HR) for 1-year increase in partner's age: 1.00, 95% confidence interval (CI): 0.97 to 1.03] or categorically (man ≥5 years older: HR, 0.98; 95% CI: 0.81 to 1.20; man ≥10 years older: HR, 0.98; 95% CI: 0.67 to 1.43). These results were robust to adjustment for known sociodemographic and behavioral HIV risk factors and did not vary significantly by women's age, marital status, education attainment, or household wealth.

Conclusions: HIV incidence in young women was very high in this rural community in KwaZulu-Natal. Partner age disparity did not predict HIV acquistion. Campaigns to reduce age-disparate sexual relationships may not be a cost-effective use of HIV prevention resources in this setting.

Abstract [3] Full-text [free] access [4]

 

Transmission networks and risk of HIV infection in KwaZulu-Natal, South Africa: a community-wide phylogenetic study.

de Oliveira T, Kharsany AB, Gräf T, Cawood C, Khanyile D, Grobler A, Puren A, Madurai S, Baxter C, Karim QA, Karim SS. Lancet HIV. 2017 Jan;4(1):e41-e50. doi: 10.1016/S2352-3018(16)30186-2. Epub 2016 Dec 1.

Background: The incidence of HIV infection in young women in Africa is very high. We did a large-scale community-wide phylogenetic study to examine the underlying HIV transmission dynamics and the source and consequences of high rates of HIV infection in young women in South Africa.

Methods: We did a cross-sectional household survey of randomly selected individuals aged 15-49 years in two neighbouring subdistricts (one urban and one rural) with a high burden of HIV infection in KwaZulu-Natal, South Africa. Participants completed structured questionnaires that captured general demographic, socioeconomic, psychosocial, and behavioural data. Peripheral blood samples were obtained for HIV antibody testing. Samples with HIV RNA viral load greater than 1000 copies per mL were selected for genotyping. We constructed a phylogenetic tree to identify clusters of linked infections (defined as two or more sequences with bootstrap or posterior support ≥90% and genetic distance ≤4·5%).

Findings: From June 11, 2014, to June 22, 2015, we enrolled 9812 participants, 3969 of whom tested HIV positive. HIV prevalence (weighted) was 59·8% in 2835 women aged 25-40 years, 40·3% in 1548 men aged 25-40 years, 22·3% in 2224 women younger than 25 years, and 7·6% in 1472 men younger than 25 years. HIV genotyping was done in 1589 individuals with a viral load of more than 1000 copies per mL. In 90 transmission clusters, 123 women were linked to 103 men. Of 60 possible phylogenetically linked pairings with the 43 women younger than 25 years, 18 (30·0%) probable male partners were younger than 25 years, 37 (61·7%) were aged 25-40 years, and five (8·3%) were aged 41-49 years: mean age difference 8·7 years (95% CI 6·8-10·6; p<0·0001). For the 92 possible phylogenetically linked pairings with the 56 women aged 25-40 years, the age difference dropped to 1·1 years (95% CI -0·6 to 2·8; p=0·111). 16 (39·0%) of 41 probable male partners linked to women younger than 25 years were also linked to women aged 25-40 years. Of 79 men (mean age 31·5 years) linked to women younger than 40 years, 62 (78·5%) were unaware of their HIV-positive status, 76 (96·2%) were not on antiretroviral therapy, and 29 (36·7%) had viral loads of more than 50 000 copies per mL.

Interpretation: Sexual partnering between young women and older men, who might have acquired HIV from women of similar age, is a key feature of the sexual networks driving transmission. Expansion of treatment and combination prevention strategies that include interventions to address age-disparate sexual partnering is crucial to reducing HIV incidence and enabling Africa to reach the goal of ending AIDS as a public health threat.

Abstract access [5] 

 

Age-disparate relationships and HIV incidence in adolescent girls and young women: evidence from Zimbabwe.

Schaefer R, Gregson S, Eaton JW, Mugurungi O, Rhead R, Takaruza A, Maswera R, Nyamukapa C. AIDS. 2017 Jun 19;31(10):1461-1470. doi: 10.1097/QAD.0000000000001506.

Objective: Age-disparate sexual relationships with older men may drive high rates of HIV acquisition in young women in sub-Saharan Africa, but evidence is limited. We investigate the association between age-disparate relationships and HIV incidence in Manicaland, Zimbabwe.

Design: A general-population open-cohort study (six surveys) (1998-2013).

Methods: A total of 3746 young women aged 15-24 years participated in consecutive surveys and were HIV-negative at the beginning of intersurvey periods. Last sexual partner age difference and age-disparate relationships [intergenerational (≥10 years age difference) and intragenerational (5-9 years) versus age-homogeneous (0-4 years)] were tested for associations with HIV incidence in Cox regressions. A proximate determinants framework was used to explore factors possibly explaining variations in the contribution of age-disparate relationships to HIV incidence between populations and over time.

Results: About 126 HIV infections occurred over 8777 person-years (1.43 per 100 person-years; 95% confidence interval = 1.17-1.68). Sixty-five percent of women reported partner age differences of at least 5 years. Increasing partner age differences were associated with higher HIV incidence [adjusted hazard ratio (aHR) = 1.05 (1.01-1.09)]. Intergenerational relationships tended to increase HIV incidence [aHR = 1.78 (0.96-3.29)] but not intragenerational relationships [aHR = 0.91 (0.47-1.76)]. Secondary education was associated with reductions in intergenerational relationships [adjusted odds ratio (aOR) = 0.49 (0.36-0.68)]. Intergenerational relationships were associated with partners having concurrent relationships [aOR = 2.59 (1.81-3.70)], which tended to increase HIV incidence [aHR = 1.74 (0.96-3.17)]. Associations between age disparity and HIV incidence did not change over time.

Conclusion: Sexual relationships with older men expose young women to increased risk of HIV acquisition in Manicaland, which did not change over time, even with introduction of antiretroviral therapy.

Abstract [6]  Full-text [free] access  [7]

 

HIV prevalence and ART use among men in partnerships with 15-29 year old women in South Africa: HIV risk implications for young women in age-disparate partnerships.

Evans M, Maughan-Brown B, Zungu N, George G. AIDS Behav. 2017 Aug;21(8):2533-2542. doi: 10.1007/s10461-017-1741-6.

This study assesses whether men's ART use mitigates HIV-risk within age-disparate partnerships. Using data from the 2012 South African National HIV survey, we analyzed differences in HIV prevalence and ART use between men in age-disparate and age-similar partnerships with young women aged 15-29 using multiple logistic regression analyses. Within partnerships involving women 15-24 years old, men in age-disparate partnerships were more likely to be HIV-positive (5-9 year age-gap: aOR 2.8, 95%CI 1.4-5.2; p < 0.01; 10+ year age-gap: aOR 2.2, 95%CI 1.0-4.6; p < 0.05). Men in age-disparate partnerships who were 5-9 years older were significantly more likely to be HIV-positive and ART-naïve (aOR 2.4, 95%CI 1.2-4.8; p < 0.05), while this was not the case for men 10+ years older (aOR 1.5, 95%CI 0.7-3.6; p = 0.32). No evidence was found that 25-29 year old women were at greater HIV-risk in age-disparate partnerships. Our results indicate that young women aged 15-24 have a greater likelihood of exposure to HIV through age-disparate partnerships, but ART use among men 10+ years older could mitigate risk.

Abstract access [8] 

 

Africa [13]
South Africa [14], Zimbabwe [15]
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