September 29, 2006
The age of people being diagnosed and living with chronic HIV infection has continued to increase during the last decade. Consequently, there is a need to better define the clinical characteristics of these individuals as well as their response to antiretroviral therapy. Because of the fact that this is an emerging population, data from existing cohorts and clinical trials are limited in their ability to define differences by age. Importantly, several studies have suggested that there are differences in response to antiretroviral therapy in older individuals.
The current study1 presented by Gemma Navarro evaluated patients identified and followed in the PISCIS cohort, a prospective cohort study that includes HIV-infected individuals who were newly diagnosed beginning in January 1998 and followed at 11 hospitals of Catalonia and Balearic Islands through December 2004.
At the time of diagnosis, the investigators divided the population into two groups by age. One group included patients who were 50 years old or older (n = 490) and the other group included patients who were 18 to 40 years old (n = 3,832). Baseline characteristics of the patients in the two groups are summarized in the table below. The group of patients who were 50 years old or older was more frequently male, acquired HIV by sexual transmission, was less likely to be hepatitis C antibody positive and more likely to have an AIDS diagnosis at the time of presentation.
Consistent with this, the older group also had higher plasma HIV RNA levels and lower CD4+ cell counts at presentation. Patients were followed longitudinally. During the course of follow-up, the older group was more likely to have undetectable viral loads: 86% versus 68% after one year (P < .001), although this difference was no longer significant after five years.
CD4+ cell counts also increased to a greater extent in the older patients, although remaining lower than that of the younger cohort throughout the course of follow-up. Finally, the older group had a greater risk of progression to AIDS (P < .001), death (P < .001) and a shorter survival (P < .001) than did the younger group.
|Baseline Characteristics at Diagnosis||18-40 Years||>50 Years||P-Values|
|Sexual Transmission (%)||29||52||<.001|
|HCV Antibody Positive (%)||45||14||<.001|
|Mean HIV RNA (log10 copies/mL)||4.4||4.8||<.001|
|Mean CD4+ Cell Count (cells/µL)||361||229||<.001|
It is difficult to draw any strong conclusions from cohort studies, although they do provide some insight into select issues surrounding unique patient populations. This study suggests that people who are 50 years of age or older present to care later in the course of disease. Nevertheless, they did appear to respond well to therapy with a good immunologic response. This data does not allow for a direct comparison in the degree of immune reconstitution by age, which other studies suggest is attenuated in older individuals.2 While more research is needed to further define the effect of age on HIV disease, at the very least this study emphasizes the need to consider all people at risk for HIV regardless of their age, so that HIV testing can be performed prior to their developing an AIDS-defining condition.
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