CD4:CD8 ratio recovery slows among people starting antiretroviral treatment after age 60, reports UK-based study

At endpoints of five and 10 years of HIV treatment, the CD4:CD8 T-cell ratio–a predictor of non-AIDS defining diseases–recovered more slowly among people who had begun treatment at older ages than those who started antiretroviral therapy (ART) when younger, according to research conducted in the United Kingdom.

About This Study

“Association of age at ART initiation with CD4:CD8 ratio recovery among virally suppressed people living with HIV, 2001–2019” was published online on Nov. 28, 2023, in AIDS. The lead author is Clare J. Holden, Ph.D., of the Institute for Global Health at University College London, United Kingdom.

Key Research Findings

This single-site study in London assessed the relationship between age when starting antiretroviral treatment and the CD4:CD8 T-cell ratio in a sample of 1,859 virally suppressed people, ranging from 20-78 years old (75% male, 56% white). Participants began care between 2001 and 2015. A CD4:CD8 ratio > 1 is desirable for overall health.

The size of the age groups differed significantly, ranging from nine participants in the baseline 70-79 years group to 748 participants in the baseline 30-39 years group. Participants were removed from analysis if their HIV rebounded to a viral load >1,000 copies/mL or if they died. By year five, 30% of the baseline sample was censored; by year 10, 61% of the baseline sample was removed. This censoring especially affected participants > 60 years old at treatment start.

The overall baseline CD4:CD8 ratio was 0.24, which increased to 0.77 by year five and 0.88 by year 10. The increase was slower in older people, with a median 0.44 by year five among the oldest group (age 70-79 years at baseline) compared to a median 0.85 at that timepoint in the youngest group (age 20-29 years at baseline). These results did not differ by year of treatment start after data were adjusted for baseline CD4 count (a proxy for how long someone lived with the virus before beginning antiretroviral treatment).

Discussion Highlights and Implications for Practice

The authors pointed out that the study sample included only people who achieved viral suppression on antiretroviral treatment within six months and then maintained it over time, so it is not representative of the overall HIV population.

Other reported study limitations included much smaller sample sizes at year 10 (especially in people older than 60 years), potential survivor bias, and lack of data on individual adherence or cytomegalovirus coinfection.

The finding that ratio recovery did not improve with newer HIV medications–i.e., among people starting treatment in more recent years–may be related to the fact that all participants were virally suppressed, the researchers noted. Older people have been shown to be more adherent to treatment – affecting censoring due to viral rebound. In addition, because the older population died more often than younger participants, this affected censoring due to death.

The researchers pointed out that as more studies investigate CD4:CD8 ratio recovery among older people who have been on HIV treatment for a very long time, this will provide further information on differing rates of response to antiretroviral treatment.

By Barbara Jungwirth