HIV crosses the blood brain barrier and infects cells of the brain, usually shortly after infection. As a result long term HIV infection may cause cognitive changes and HIV- associated dementia (HAD).

Prior to the advent of HAART, HAD was very common, but in countries with access to treatments it is now extremely rare unless HIV is diagnosed very late.

Some HIV drugs are more effective at crossing the blood brain barrier than others so it is important to be monitored for any early signs of dementia.

There is a milder cognitive disorder that some people with HIV get that is not necessarily a sign of early dementia.

Dementia and cognitive issues are associated with ageing independently of HIV.