BACKGROUND: aging of people with human immunodeficiency virus (HIV) is a worldwide reality, and age-related conditions, including disability, have also increased. Efforts are being made to search for more specific markers of immune system malfunction, which serve as good predictors of adverse health-related outcomes. Therefore, this study aimed to determine the relationship between the CD4+/CD8+ ratio and functional decline in activities of daily living (ADL). METHODS: participants in this longitudinal study underwent a standardized comprehensive geriatric assessment by trained staff, using validated tools. Functional decline in ADL was established by the delta resulting from the subtraction of the score on the Barthel index at T1 minus the score at T0 (baseline). Multivariate linear regression analyses were used to determine the independent relationship between the CD4+/CD8+ ratio and ADL decline . RESULTS: mean age was 57.9 (SD 6.6; range 50-84 years), and 82.7% were men. Eleven of the 209 participants had disability for ADL at baseline. Multivariate linear regression analysis showed an inverse relationship between the log of CD4+/CD8+ ratio at baseline and the delta of Barthel index even after adjustment for multiple confounders (β = -1.68, 95% CI -3.02 to -0.33; p = 0.01). CONCLUSIONS: a CD4+/CD8+ ratio of <1 predicts the development of functional decline in ADL. This ratio can be a useful marker to identify people at risk of disability and should be considered for the tailored management of older adults with HIV.< Réduire