Over 50s have lower viral load, no link found to type of therapy, adherence or CD4 count

HIV-positive people aged over 50 have lower viral loads than younger adults, even after adjusting for anti-HIV therapy, adherence and stage of HIV disease, according to a poster presentation from the University of Miami to the Second International AIDS Society Conference on HIV Pathogenesis and Treatment in Paris.

Earlier studies have suggested that older patients have lower viral loads, although better adherence to HAART and other factors have been offered as explanations. The investigators in Miami wished to establish if older patients with HIV symptoms of HIV infection or AIDS did have lower viral loads than younger adults at a similar disease stage.

The longitudinal study involved 72 patients aged 50 or above, with an average age of 55 years and 63 individuals aged between 18 and 39, average age 33 years. Older patients were more likely to be male (83% versus 46%), white (50% versus 14%), have a higher income (31% over $20,000 per year versus 9%), and to be gay (48% versus 23%).

Variables included in the investigators analysis included HIV disease stage, adherence to HAART, CD4 cell count, duration of diagnosed HIV infection, alcohol and drug use, and unprotected sexual activity.

CD4 cell counts were higher in the older patients than the younger ones (p=.02), but the majority of patients in both groups showed signs of moderate immune suppression and had a CD4 cell count between 200 and 499 cells/mm³. Levels of adherence were comparable between the over 50s and under 40s, and there were no substantive differences in drug use, although the older patients showed greater alcohol use (p=0.06). Younger patients showed a higher frequency of sexually transmitted infections (39%) than the over 50s (20%).

There were significant differences in viral load between the two groups, with 50% of older patients having a viral load below 50 copies/mL compared to 31.7% of the under 40s.

This age difference remained significant when antiretroviral use, adherence, and disease stage were controlled for (p

The investigators conclude that the differences in viral load observed in their study have clinical as well as statistical significance. They suggest that the differences in viral load could be because of differences between the immune systems of older and younger patients. In particular, older patients could have greater numbers of mature cytotoxic T lymphocte effector cells. They suggest that further studies are still needed which should focus on socio-economic status, nadir CD4 cell counts, viral load before HAART, age at HIV diagnosis and the length of untreated HIV infection.