Age at Antiretroviral Therapy Initiation Predicts Immune Recovery,Death,and Loss to Follow-Up Among HIV-Infected Adults in Urban Zambia

Abstract

We analyzed the association of age at antiretroviral therapy (ART) initiation with CD4⁺ T cell count recovery, death, and loss to follow-up (LTFU) among HIV-infected adults in Zambia. We compared baseline characteristics of patients by sex and age at ART initiation [categorized as 16–29 years, 30–39 years, 40–49 years, 50–59 years, and 60 years and older]. We used the medication possession ratio to assess adherence and analysis of covariance to measure the adjusted change in CD4⁺ T cell count during ART. Using Cox proportional hazard regression, we examined the association of age with death and LTFU. In a secondary analysis, we repeated models with age as a continuous variable. Among 92,130 HIV-infected adults who initiated ART, the median age was 34 years and 6,281 (6.8%) were aged ≥50 years. Compared with 16–29 year olds, 40–49 year olds (–46 cells/mm³), 50–59 year olds (–53 cells/mm³), and 60+ year olds (–60 cells/mm³) had reduced CD4⁺ T cell gains during ART. The adjusted hazard ratio (AHR) for death was increased for individuals aged ≥40 years (AHR 1.25 for 40–49 year olds, 1.56 for 50–59 year olds, and 2.97 for 60+ year olds). Adherence and retention in care were poorest among 16–29 year olds but similar in other groups. As a continuous variable, a 5-year increase in age predicted reduced CD4⁺ T cell count recovery and increased risk of death. Increased age at ART initiation was associated with poorer clinical outcomes, while age <30 years was associated with a higher likelihood of being lost to follow-up. HIV treatment guidelines should consider age-specific recommendations.