Background:  Epidemiologic studies, in pre-HAART era suggested that age may be a risk factor for HIV dementia. Even though increased survival of treated patients has been associated with an increased development of chronic diseases, the effect of HAART on risk of cognitive impairment associated to increasing age has not been fully clarified.

Methods:  Nested longitudinal study on a national cohort of HIV-infected patients with neurologic diseases. For statistics, crude and adjusted OR by logistic regression and Kaplan-Meier estimates and Cox regression for survival were employed.

Results:  From 2000 to 2003, 195 patients with HIV encephalopathy (53% HIV dementia, 47% MCMD) were notified. The overall prevalence was 21% with an increasing annual rate (p = 0.01). Median age was 42 years (IQR 37 to 48); 35% of patients aged 20 to 39 years (group A), 45% aged 40 to 49 years (group B), and 20% aged ≥50 years (group C). A previous antiretroviral exposure was present in 45% of patients, and 28% were receiving HAART at diagnosis. Median CD4 cell count and plasma HIV-1 RNA were 81 cells/μL (IQR 27 to 202) and 5.04 log₁₀ copies/mL (IQR 4.20 to 5.55), respectively. Stratifying patients according to age and exposure to antiretrovirals, among naïve patients the prevalence of HIV encephalopathy was higher in older subjects:  13.7% in the group A, 28.3% in the group B, and 37.5% in the group C (OR for group C vs A 3.83; p <0.001). The same proportions for HIV dementia were 7.2%, 15.3%, and 27.3% (OR 4.89; p <0.001). In experienced patients no significant increase of HIV encephalopathy (OR 1.46; p = 0.13) or HIV dementia (OR 1.66; p = 0.18) for older age was observed. In naïve patients, older age was independently associated with an increased risk of HIV encephalopathy (OR 4.42 95% CI 2.26 to 8.61) and of HIV dementia (OR 6.4; 95% CI 2.82 to 14.68), whereas in experienced only higher CD4 cell count and lack of previous AIDS were found as HIV encephalopathy risk factors. An increased prevalence of HIV dementia among older (group C) naïve patients respect to older experienced patients was detected (p = 0.05). No significant effect on survival for older age, CD4 count, HIV-1 RNA or receiving HAART after neurologic diagnosis (time-dependent covariate) was observed.

Conclusions:  HAART appears to change the relationship between aging and developing HIV dementia, conferring a neuroprotective effect to older patients and affecting the increased prevalence rate of HIV dementia with increasing age. Increasing prevalence trend and enhanced risk of HIV encephalopathy at higher CD4 count suggests new challenges for cognitive disorders in HAART treated population.

Keywords: HIV dementia; age; HIV encephalopathy