Immunologic response to antiretroviral therapy by age among treatment-naive patients in Sub-Saharan Africa.

OBJECTIVE: To estimate the association between age at antiretroviral therapy (ART) initiation and immunologic response over time by stratum of baseline CD4 cell counts. DESIGN: Retrospective cohort analysis of data pooled from four President's Emergency Plan for AIDS Relief funded countries in Sub-Saharan Africa. METHODS: General linear models were used to estimate the mean CD4 cell count by age group within groups defined by baseline CD4 cell count. Kaplan-Meier methods were used to estimate time to achieving a CD4 cell count of at least 500 cells/µl by age group and stratified by baseline CD4 cell count. RESULTS: A total of 126 672 previously treatment-naive patients provided 466 482 repeated CD4 cell count measurements over 4 years of ART. The median baseline CD4 cell count for all age groups was less than 200 cells/µl. Patients aged 30-39, 40-49, 50-59, and 60 and older at ART initiation had significantly lower mean CD4 cell counts in most strata and at most time points than those 20-29 years old. Compared with those 20-29, all older age groups had a significantly longer time to, and lower rate of, achieving a CD4 cell count of 500 cells. CONCLUSION: Age is associated with the magnitude of CD4 cell gain and the amount of time it takes to gain cells at different levels of baseline CD4 cell count. The delay in achieving a robust immune response could have significant implications for the risk of tuberculosis reactivation as well as comorbidities associated with age in the management of older HIV-infected patients.