Results from a recent study indicate that older HIV-positive individuals have a higher level of a particular type of brain impairment called dispersion, which causes inconsistent cognitive function, compared to HIV-negative individuals of a similar age and younger HIV-positive and HIV-negative individuals.

The authors hypothesized that the problems are due to accelerated aging in the HIV-positive population, which has been observed in other studies.

“These findings suggest that individuals infected with HIV who are 50 years of age or older may experience a type of cognitive problem that uninfected individuals typically show at a later age (e.g., in their 60’s and 70’s),” said Erin Morgan, a researcher at the University of California, San Diego and lead author of the study.

“It is possible that older HIV-positive persons with increased dispersion may notice these cognitive fluctuations in their daily life, which could interfere with their ability to successfully carry out important everyday activities (e.g., managing medications and/or finances),” she added.

The authors of the study plan to conduct further studies on the underlying causes of increased dispersion in people with HIV.

“Our ultimate goal is to find effective ways to treat dispersion (and other cognitive deficits in HIV), which we hope will have positive effects on the daily functioning and quality of life of persons living with HIV infection,” said Morgan.

People with HIV and AIDS commonly experience neurological problems that can lead to a decline in brain function. With the advent of highly active antiretroviral therapy (HAART), many of the most severe forms of neurological dysfunction associated with HIV have become less common. However, rates of milder forms of brain impairment have not decreased with HAART and still affect around half of people with HIV (see related AIDS Beacon news).

In addition, HAART has contributed to the growing population of HIV-positive individuals aged 50 and older as people with HIV live longer. The rate of HIV infection in older adults also continues to rise.

Previous studies have shown that older HIV-positive adults are at an increased risk for neurological problems, especially dementia and cognitive impairment. According to the study authors, adults with HIV-associated cognitive impairment are less likely to properly adhere to HAART and therefore may face a poorer prognosis and significant HIV-related health problems.

In this study, the authors investigated how a particular type of cognitive impairment, called dispersion, was associated with HIV status and aging.

Dispersion is a disorder in which a person has large variability in their performance on similar tests – in other words, inconsistent test results. According to the study authors, dispersion has been linked to risk of later dementia and cognitive decline.

The study included 126 HIV-positive adults and 40 HIV-negative adults. Twenty-nine percent of the HIV-positive participants and 35 percent of the HIV-negative participants were over the age of 50. Most HIV-positive participants (89 percent) were male and a majority (60 percent) was Caucasian.

Results showed that inconsistency in performing mental tasks was significantly worse in older HIV-positive participants compared to both younger HIV-positive participants and older HIV-negative study participants.

HIV-positive participants also showed measurable dispersion earlier than expected, at an average age of 54, compared to 65 to 70 in the general population.

In contrast, measures of dispersion did not vary by age in the HIV-negative group. In addition, being HIV positive was not associated with higher risk of dispersion in participants under the age of 50.

Results also showed that older HIV-positive participants had significantly lower nadir CD4 (white blood cell) counts and higher rates of hepatitis C co-infection compared to younger HIV-positive participants. The nadir CD4 cell count is defined as the lowest CD4 cell count measured after HIV infection.

However, even after taking these factors into account, older age was significantly linked with higher risk of dispersion for HIV-positive study participants.

For more information, please see the study in Neuropsychology (abstract).