Washington University logoOver half of HIV patients seem to face memory problems along with other cognitive impairments as they age. Doctors claim to have very little information about the underlying causes of this loss.

However a new research from Washington University School of Medicine in St. Louis reveals that cognitive deficits related to HIV appear to share a common association with Alzheimer’s-related dementia. It could be attributed to low levels of the protein amyloid beta in the spinal fluid. On examining the biomarkers in the fluid surrounding the brain and spinal cord, the experts claimed to have been able to distinguish patients with HIV-related cognitive impairments from patients with mild Alzheimer’s disease.

Citing this distinction as essential, the scientists suggest that as patients with HIV age, some of them appear to have developed cognitive deficits related to HIV and others to Alzheimer’s. Potential treatments that seem to have been lined up for improvement in memory and thinking may apparently not function for both the conditions.

“HIV patients with cognitive dysfunction don’t have early Alzheimer’s – although some of the symptoms may be similar,” comments lead author David Clifford, M.D., an authority on the neurological complications of HIV and director of Washington University’s AIDS Clinical Trials Unit. “The underlying biology of both conditions may be related to amyloid, and we think this clue can help us find the cause of cognitive impairment in HIV patients.”

As part of the new research, the investigators observed the spinal fluid of 49 HIV patients with cognitive impairments along with 21 HIV patients with normal cognitive function. They also looked at 68 patients with mild Alzheimer’s and 50 normal, healthy ‘controls’. While the Alzheimer’s patients were noted to have been older than the controls at an average age of 74 as compared to the latter’s average age of 50, impaired HIV patients had an average age of 48 and cognitively normal HIV patients had average age of 43.

The spinal fluid was tested by the researchers for the presence of amyloid beta. The latter is known to be a protein that folds and accumulates in the brains of Alzheimer’s patients. It is believed to play a crucial part in fueling the brain damage that could be characterizing the disease. The team also seems to have observed other biomarkers linked with Alzheimer’s, including tau which is a protein found in tangled nerve fibers in Alzheimer’s patients.

Clifford and his colleagues anticipated the discovery of low levels of the protein in samples of the Alzheimer’s patients they analyzed. When amyloid beta collects in the brains of Alzheimer’s patients, levels decrease in the spinal fluid was what they expected to find. Surprisingly the team uncovered similar low levels in the spinal fluid of HIV patients with cognitive dysfunction. Significantly lower amyloid beta levels as compared to HIV patients without cognitive impairments and the normal controls were found in both groups of patients. These lower levels could probably point that amyloid beta in the brain may modify the normal turnover of the protein in the body.

In 2005 in a smaller analysis, Australian and European researchers seem to have discovered a link between HIV-related cognitive deficits and amyloid beta. Clifford though assumed the finding to be an artifact and seems to have started the present research largely to disprove it.

“I really did not expect the biology of HIV cognitive dysfunction to be related to Alzheimer’s,” Clifford mentions. “If you look at the brains of HIV patients with cognitive impairments, they don’t look like Alzheimer’s brains – they don’t have the same atrophy or a plethora of plaques and tangles characteristic of Alzheimer’s.”

The similarity to Alzheimer’s disease appears to end at low amyloid beta. Researchers suggest that patients who exhibit mild Alzheimer’s seem to have considerably higher levels of tau as against either group of HIV patients or normal controls. Clifford is of the opinion that this finding strongly suggests Alzheimer’s and HIV cognitive dysfunction is not one and the same.

HIV-related cognitive impairment is suspected by him to occur due to low levels of the virus that mask in the brain. This may keep them beyond the reach of drugs that can’t easily cross the blood-brain barrier. Low-grade inflammation in the brain probably driven by the virus could be another reason. Anti-retroviral therapy was being administered to all HIV patients involved in the research.

“I am almost certain the dementia in AIDS patients is linked to HIV and not to anti-retroviral drugs – we see it even in patients who haven’t received HIV therapy,” Clifford shares. “However, the more subtle impairment may be in some way associated with a change in the way the body processes amyloid beta. This will certainly be an important area of future research.”

A major problem among the estimated 1 million Americans living with HIV, cognitive dysfunction is often mild but may affect a person’s daily life, relationships and ability to hold a job. Impairments comprise of memory difficulties, processing of complex information and making decisions. Via potent drug cocktails that seem to keep a tab on the virus, as HIV patients live longer, these problems are expected to worsen.

The finding is published in the journal Neurology.