Frailty index (per 0.01 increase) and CD4 count had an inverse relationship below 900 cells/μL (a total of 9048 observations were analysed, ß = -0.45, -0.58 to -0.32, p<0.001, per 100 cells/μL) and a borderline relationship above 900 cells/μL (1638 observations, ß = 0.23, 0.0002 to 0.46, p = 0.049, per 100 cell/μL) after adjustment for age, sex, and duration of HIV infection. Here, CD4 is linked to HIV infectious disease.