The prevalence, incidence, and sociodemographic risk factors of HIV among older adults in sub-Saharan Africa (AWI-Gen): a multicentre, longitudinal cohort study.

BACKGROUND

Sub-Saharan Africa's ageing population includes a rising number of adults aged 50 years and older living with HIV. Although antiretroviral therapy (ART) has extended life expectancy, data on HIV incidence and treatment outcomes among older adults remain scarce. To inform targeted public health interventions, we aimed to examine the prevalence and incidence of HIV, as well as sociodemographic determinants associated with HIV acquisition and treatment outcomes, among older adults in sub-Saharan Africa.

METHODS

AWI-Gen is a multicentre, longitudinal cohort study. We assessed data from random community-based samples of adults aged 40-60 years collected between Aug 5, 2013, and Aug 19, 2016 (wave 1) and of adults aged 40 years and older collected between Jan 24, 2019, and Nov 23, 2022 (wave 2) from Nairobi (Kenya) and from Soweto, Agincourt, and Dikgale Mamabolo Mothiba (South Africa). Sociodemographic data were collected through interviewer-administered questionnaires and structured interviews. The primary outcome was HIV status at both wave 1 and wave 2, classified as either HIV-positive or HIV-negative. We evaluated the prevalence and incidence of HIV, ART coverage, and self-reported HIV awareness and used logistic regression to examine risk factors associated with HIV acquisition and treatment outcomes.

FINDINGS

Among 7919 participants in wave 1 who were recruited and followed up, 6505 (82·1%) participants were aged 40-60 years, of whom 5730 (88·1%) contributed HIV-related data. 3148 (54·9%) participants were women and 2582 (45·1%) were men. In wave 2, 4520 participants from wave 1 were followed up with an additional 579 participants recruited. 5076 (99·5%) participants were aged 40 years and older, of whom 4931 (97·1%) contributed HIV-related data. 2767 (56·1%) participants were women and 2164 (43·9%) were men. Overall, 1271 (22·2%) of 5730 participants in wave 1 and 1073 (21·8%) of 4931 participants in wave 2 were living with HIV, with regional variability (χ p<0·0001) and higher prevalence in women than in men (χ p<0·0001). Prevalence was highest among individuals aged 40-45 years (454 [26·7%] of 1698 participants) in wave 1 and those aged 46-50 years (297 [29·9%] of 994 participants) in wave 2, decreasing significantly in older age groups (χ p<0·0001). Overall HIV incidence was 0·35 per 100 person-years (95% CI 0·26-0·48), with a reduced risk of seroconversion in participants aged 51-55 years (incidence rate ratio [IRR] 0·42 [95% CI 0·17-0·93]; p=0·039) and 56-60 years (0·19 [0·05-0·52]; p=0·0033). Compared with participants with formal education, incidence among those with no formal education was nearly four times higher (IRR 0·96 [95% CI 0·50-1·85] vs 0·26 [0·16-0·44]). Women and men residing in rural areas showed consistently higher predicted probabilities of HIV status than their counterparts in urban settings. The accuracy of self-reported HIV-positive status improved from 55·5% (95% CI 51·1-59·8) in wave 1 to 76·7% (73·1-80·0) in wave 2. ART coverage also increased between wave 1 (250 [90·3%] of 277 participants who reported a positive HIV test result) and wave 2 (404 [94·2%] of 429 participants).

INTERPRETATION

The findings emphasise the complex interplay of age, education, gender, and location in shaping HIV risk. Although ART coverage has improved, older adults face considerable barriers to HIV prevention, including educational disparities and gender inequities, particularly in rural settings. Tailored interventions targeting older populations are essential to address these gaps because the risk of HIV acquisition, albeit generally lower than in younger populations, remains noteworthy.

FUNDING

National Human Genome Research Institute, the National Institute of Environmental Health Sciences of the US National Institutes of Health, and the Department of Science and Innovation, South Africa.