Although HIV doesn't directly infect neurons, it appears that once it has crossed the blood-brain barrier, it affects supporting cells that can release immune factors that harm neurons. New techniques used on 26 subjects with HIV and 25 matched controls have now found that those with HIV showed decreased brain blood flow to levels roughly equivalent to readings seen for uninfected individuals 15 to 20 years older. It is suggested that HIV, medications, or both, are accelerating what is a normal age-related process. It’s estimated that 14-18% of AIDS patients in the U.S. are more than 50 years old, and this proportion is rapidly growing.
 . HIV Infection and Aging Independently Affect Brain Function as Measured by Functional Magnetic Resonance Imaging. The Journal of Infectious Diseases [Internet]. 2010 ;201(3):336 - 340. Available from: http://dx.doi.org/10.1086/649899