Objective: To study immunologic and clinical responses to HAART in patients over 50 years old.
Design and methods: A prospective cohort study which included 68 hospitals in France. A total of 3015 antiretroviral-naive patients, 401 of whom were aged 50 years or over, were enrolled following initiation of HAART. The influence of age on the mean CD4 cell count increase on HAART was studied by using a two-slope mixed model. Progression, defined by the occurrence of a new AIDS-defining event (ADE) or death, was studied by Cox multivariate analyses.
Results: Among patients with baseline HIV RNA above 5 log copies/ml, CD4 mean increase during the first 6 months on HAART was +42.9 x 10(6) cells/l per month in patients under 50 years and +36.9 x 10(6) cells/l per month in patients over 50 years (P < 0.0001); subsequently, the respective monthly changes were +17.9 and +15.6 x 10(6) cells/l per month (P < 0.0001). Similar trends were observed in patients with baseline HIV RNA below 5 log copies/ml, and also after stratification for the baseline CD4 cell count. After a median follow-up of 31.5 months, 263 patients had a new ADE and 44 patients died. After adjustment for baseline characteristics, older patients had a significantly higher risk of clinical progression (hazard ratio (HR) = 1.52 [95% confidence interval (CI), 1.15-2.00]) and were more likely to achieve a viral load below 500 copies/ml [HR = 1.23, (95% CI, 1.11-1.38)].
Conclusion: Patients over 50 years of age have an immunologic response to HAART. However, their CD4 cell reconstitution is significantly slower than in younger patients, despite a better virologic response. This impaired immunologic response may explain their higher risk of clinical progression.