For the most part, high rates of cognitive impairment among people with HIV—including memory loss, difficulty concentrating and declining mental abilities—are due to the same factors that affect HIV-negative people. A recent French study examined 400 HIV-positive adults and found that 59 percent showed cognitive impairment, a rate similar to that found in other studies.

The researchers found that the main risk factors for cognitive impairment were advanced age, low education level, anxiety, depression, cardio vascular disease, high cholesterol and a history of brain damage.

 David M. Simpson, MD, director of the Neuro-AIDS Program at Mount Sinai Medical Center in New York City, cautions, “One of the potential misinterpretations of these data is that all of the cognitive impairment that one encounters in HIV is due to all these other factors. And that's just not the case.”

Simpson points out that the French study, after excluding all non-HIV-related risk factors, still found about a 10 percent rate of cognitive impairment. And that rate, he says, may even be a low estimate.

While this study could find no link between cognitive problems and viral load, CD4 count or the use of antiretrovirals, studies from the pre-ARV era found that those with poorly controlled HIV and depleted immune systems did have a greater risk of mental decline.