Patients who are aged in their 30s at the time of infection with HIV have a better response to HIV treatment than individuals aged between 18 – 29, according to a US study published in the September 1st edition of the Journal of Acquired Immune Deficiency Syndromes.
Before effective HIV treatment became available, older age at the time of HIV diagnosis was associated with faster HIV disease progression. Studies conducted since the introduction of combination antiretroviral therapy have yielded conflicting results about the impact of age on the outcome of antiretroviral therapy.
But these studies have often lacked reliable information about the duration of HIV infection and the definition of “older” age differed between studies.
Investigators from the Tri-Service AIDS Clinical Consortium (TACC) Natural History Study (NHS), which involves HIV-positive personnel from the US armed services and Department of Defence, looked at the medical records of 563 patients with a known date of HIV seroconversion. They divided these patients into age groups at the time of HIV seroconversion (18 – 29, 30 – 39, 40 and over) and compared changes in viral load, CD4 cell count and the risk of HIV disease progression or death after the initiation of combination antiretroviral therapy in the different age groups.
There were no significant differences in the baseline characteristics of the age groups.
After six months of combination antiretroviral therapy, 69% of patients aged between 18 – 29 had an undetectable viral load compared to 80% of those aged 30 – 39 at the time of seroconversion, a difference that was statistically significant (p = 0.002).
But the investigators found important racial differences. African-American patients had the lowest overall probability of having an undetectable viral load in any age group, but the investigators found that the probability of this outcome increased with age (for age 25, HR = 1.2, for age 40, HR = 1.7). By contrast, the white patients most likely to have an undetectable viral load were those aged 30 at the time of HIV seroconversion (HR = 3.4, 95% CI, 1.9 – 3.4), but white patients aged 40 at the time of seroconversion were significantly less likely to achieve this outcome (HR = 2.0, 95% CI, 1.1 – 3.7). For patients of other ethnicities, older age at seroconversion was associated with an increased likelihood of achieving an undetectable viral load after six months (for age 25 HR = 2.2, for age 40 HR = 12.1).
The investigators also found that older age at seroconversion was associated with a longer time to rebound in viral load (p
Next the investigators looked at the effect of age at seroconversion on increases in CD4 cell count after the initiation of antiretroviral therapy. In the first six months after the initiation of HIV treatment, patients aged 30 and above at seroconversion gained significantly more cells than those aged 29 and under at the time of infection with HIV (p = 0.0002), but therefore increases in CD4 cell count were comparable between the age groups.
Finally, the investigators compared rates of HIV disease progression and death after the initiation of antiretroviral therapy between the age groups. No significant associations were found between these outcomes and age at seroconversion.
“This study of a prospectively followed cohort of more than 550 adults demonstrates that increasing age at seroconversion from 18 to older than 40 years is associated with better virologic and CD4 cell responses to highly active antiretroviral therapy”, write the investigators.
They note that their study was “unique in that it examines age at seroconversion rather than age at diagnosis or age at treatment initiation, thereby eliminating any effects due to delayed diagnosis of HIV infection.”
Better adherence amongst older patients could, the investigators suggest, be the reason why older age was associated with a better chance of achieving and maintaining an undetectable viral load. Although they did not gather any information on adherence, they note that earlier studies have shown that older patients are more likely to take their antiretroviral therapy correctly.
The findings that the older patients had a faster initial increase in CD4 cell count, and that that there was no difference in the rates of HIV disease progression between age groups, are, the investigators note, in contrast to other earlier studies.
Weintrob AC et al. Increasing age at HIV seroconversion from 18 to 40 years is associated with favorable virologic and immunologic responses to HAART. J Acquir Immune Defic Syndr 49: 40 – 47, 2008.