Sept. 14 (HealthDay News) -- HIV-infected patients with declining blood platelet counts may be at increased risk for HIV-associated dementia, which causes a number of cognitive, behavioral and motor skill problems, researchers report.

Researchers at the Bloomberg School of Public Health at the Johns Hopkins University School of Medicine in Baltimore studied 396 patients with advanced HIV disease. Between 1998 and 2003, the patients were examined every six months, including mental and physical evaluations.

By the study midpoint of just over 31 months, 40 patients had developed HIV-associated dementia. The researchers found that a decline in platelet count from baseline at the start of the study was associated with the development of HIV-associated dementia within six to 12 months.

"Those HIV-infected individuals with a decline in platelets from baselines values at this lagged time point had a twofold increased risk of dementia," the study authors wrote.

"Further analyses indicated that decline from baseline platelet levels was associated with a five- to sixfold increased risk of dementia during the first two years of follow-up, but it was not associated with an increased risk of dementia after two years."

The authors said that it's "possible that individuals who do not progress rapidly to neurologic compromise differ in respect to immune activation, treatment adherence, or virologic control relative to those who develop dementia more rapidly."

They noted that CD4 cell counts and HIV RNA levels cannot be used to predict HIV-associated dementia. Further study of the link between platelet levels and HIV-associated dementia may lead to identification of a specific marker for this disease and how it develops.

The study is published in the September issue of the journal Archives of Neurology.

SOURCE: JAMA/Archives journals, news release, Sept. 10, 2007