“Interestingly, bigger waistlines were linked to decreased mental functioning more than was general obesity,” said study author J. Allen McCutchan, of the University of California, San Diego.

“This is important because certain anti-HIV drugs cause weight gain in the center of the body that is most dramatic in the abdomen, neck, chest and breasts.”

The study was performed in 130 HIV positive people from six clinics. Participants were around the age of 46 with HIV infection for an average of 13 years. Most participants were taking combinations of anti-HIV drugs called antiretroviral therapy. Impaired mental functions such as poor memory and concentration, called neurocognitive impairment (NCI), was diagnosed in 40 percent of study participants.

People with NCI had waist circumferences of an average of 39 inches, compared to 35 inches for those without memory difficulties. NCI was also linked to older age, a longer time living with HIV and diabetes in people older than 55 years. For example, five times as many people with memory problems also had diabetes compared to those with no memory problems (15 percent compared to 3 percent).

“Avoiding those HIV drugs that cause larger waistlines might protect or help to reverse NCI,” said McCutchan. “We don’t know if central obesity is causing NCI directly or is just a marker for exposure to a more direct cause such as anti-HIV drugs. People with HIV should talk to their doctors before considering changes in their anti-HIV medications.”