Intergeneration sex contributes to new HIV infections among young women in Zimbabwe

Age-disparate sexual relationships are associated with new HIV infections among young women in Zimbabwe, particularly for young women with partners ten years older or more.

The findings come from a 15-year study by Imperial College London, Zimbabwe’s Biomedical Research and Training Institute and the Zimbabwe Ministry of Health and Child Care, and is the first large scale study to track the association between intergenerational relationships and increased HIV risk before and after the introduction of antiretroviral treatment (ART) services in a country.

More than 3,700 young women aged 15 to 24 years from Manicaland in eastern Zimbabwe were included in the study. In addition to increased HIV incidence, researchers found that young women’s risk of HIV did not change over the course of the study, despite the introduction of ART services during that time.

In Zimbabwe, HIV incidence in young women is twice as high as in men of the same age. It is well known that intergenerational relationships, particularly among young women and older men, are highly prevalent in the country and in the surrounding regions. Older partners are more likely to expose a young person to unsafe sexual behaviours such as low condom use. Young women may also be motivated by the implicit assumption that sex will be exchanged for material support or other benefits.

The results provide important evidence of the way in which age-disparate relationships contribute to increased HIV incidence.  

Despite overall declines in HIV prevalence during the study, men aged 30 and above were consistently found to be more likely to have HIV than younger men, thus exposing young women in age-disparate relationships to an increased HIV risk. The study found ART coverage to be low – at 31% among HIV-positive men aged 30 to 34, and around 50% among older men ¬– and evidence of low condom use.

A fifth (20.5%) of young women in the study had partners who were older by ten years or more (intergenerational) and 44.5% had a partner of between five and nine years older (intragenerational). Although the study found a link between intergenerational relationships and increased HIV risk, young women with partners between five and nine years older were not at an increased risk of HIV. Young married women with partners 16 or more years older were found to be three times more likely to acquire HIV than those with partners 0 to15 years older.

Findings suggest the risk of young women in age-disparate relationships acquiring HIV is not affected by age group (i.e. 15 to 19 or 20 to 24), location (rural or urban), household income, marital status or orphanhood. However, young women in age-disparate relationships who report that their partners have other partners are at significantly higher risk of HIV.

The study found a strong link between low educational levels and being in an  intergenerational relationship. However, there was no difference between the likelihood that young women from urban or rural areas, and with or without surviving parents, would be in an age-disparate relationships.   

Marriage patterns in Zimbabwe are comparable to those in many other parts of East and Southern Africa, these findings therefore suggest that reducing the number of age-disparate relationships could help to decrease HIV infection rates among young women in the region.

For those in age-disparate relationships, particularly those who have concurrent partners, consistent use of condoms and pre-exposure prophylaxis could reduce young women’s risk of HIV. The protective effect of ART could also have a role to play in reducing this risk, should growing numbers of men initiate ART and achieve viral suppression.

Voluntary medical male circumcision and behaviour change programmes targeted at older men to address partner concurrency could further reduce risk. Programmes that increase female education, economic independence, and risk perception, and that engage men to change gender norms, are also needed.