One-quarter of those with HIV suffer from neurological problems — including seizures and dementia — according to a 10-year study of patients in Alberta.

A study tracking 1,651 people with HIV being treated at the Southern Alberta Clinic in Calgary between 1998 and 2008 found 404 suffered from neurological disease.

Study author Dr. Chris Power, professor of neurology at the universities of Alberta and Calgary, said the good news is that people with HIV are living much longer thanks to antiretroviral therapy.

The bad news, however, is that those who experience neurological problems face twice the risk of death compared to HIV sufferers without neurological disease.

"I was pleased in many ways that the numbers were as low as they were. I mean 25 per cent sounds like a lot, but if you compare to some U.S. clinics — and also our clinics before we had antiretroviral therapy available — our numbers are lower," said Power.

His study was published Tuesday in the peer-reviewed journal Neurology.

In addition to seizures and dementia, neurological symptoms included nerve pain in the hands and feet, memory loss, migraines and movement disorders.

Previous research suggests that while HIV doesn't directly invade nerve cells, it can cause inflammation that can damage the brain. Other research shows HIV can change the size of certain brain structures linked to learning and information processing.

Part of the problem is that the "blood-brain barrier means that a much smaller dose of HIV drugs is getting into the brain," said Power, who urged more work on developing drugs that can protect the brain from the virus.

"This is in some ways a good news story in that we're making headway — we're reducing the frequency of neurologic disease. But we've still not eradicated it completely, despite having good drugs for HIV infection," he said.