Higher-quality studies consistently find significant bivariate associations between early sexual debut and HIV. In some studies, the increase in women’s HIV infection risk seems to result from women’s later engagement in risky sexual behaviours, rather than being

directly related to early onset of sexual debut. In other studies, the increase in risk did not seem to be due to specific behavioural risk characteristics of the respondents or their sexual partners, BI 6727 suggesting that the risk may relate more to the potential for biological factors, for example, genital trauma, or other factors that have not been captured by the studies in this review. In many sub-Saharan African countries, there are disturbingly high levels of HIV infection among young women – with the discrepancies in ratios of HIV infection between 16- and 24-year-old girls compared with boys being eightfold higher in some settings.[1] Girls’ HIV vulnerability

is underpinned by a range of social norms and gender inequalities that often lead to adolescent girls commencing sex at an earlier age than adolescent boys. Young age at first sexual debut has long been discussed as a potentially important risk factor for HIV infection among women. Indeed, in Uganda in the 1990s, the rapid increase in age at first sex in urban areas was considered to be an important contributing click here factor in the decline of HIV prevalence.[2] For such reasons, initiatives to delay sexual debut have been considered as a potentially important

component of HIV prevention programmes in sub-Saharan Africa.[3] However, although girls’ early sexual debut has been posited as an important risk factor for HIV infection, the mechanisms through which this increased risk may occur these have not been fully explored. Early sexual debut could potentially increase women’s risk of HIV infection in four different ways. Firstly, early sexual debut may increase women’s HIV infection risk due to the extended duration of sexual activity, because women who started sex early have a longer duration of sexual activity, and they are therefore potentially exposed to HIV infection risk for a longer period of time.[4, 5] Although this explanation in reality is likely to be collinear with women’s age at first sex, most studies using cross-sectional survey data recruit women of different ages and therefore have different periods of exposure to sexual activity at the time of measurement irrespective of women’s age at first sex.[4, 5] Second, it may be that women who commence sex early may also be more prone to engage in risky sexual behaviours later on, such as having a high number of sexual partners, including premarital, casual partners or sex partners through transactional sex, a greater age disparity with the partner, lower rates of contraceptive and condom use, sexually transmitted infection (STI) and pelvic inflammatory diseases.