The research, published online in the journal Molecular Psychiatry, builds on previous evidence that the detection of silent beta-amyloid plaque build-up in the brain could help guide treatment decisions for patients at risk for Alzheimer’s.
“Our research found that healthy adults and those with mild memory loss who have a positive scan for these plaques have a much faster rate of decline on memory, language, and reasoning over three years,” said lead author P. Murali Doraiswamy, M.D., professor of psychiatry and director of the neurocognitive disorders program at Duke.
The study involved 152 adults (ages 50 and older) and was designed to determine whether silent pathological changes in the brain associated with Alzheimer’s and detected with positron emission tomography (PET) could predict cognitive decline.
At the beginning of the study, 69 participants had normal cognitive function, 52 had been recently diagnosed with mild cognitive impairment, and 31 were diagnosed with Alzheimer’s disease. Participants took cognitive tests and underwent brain PET scans, which uses a radioactive tracer to look for chemical signs of disease in specific tissues.
The radioactive dye, called florbetapir (Amyvid), binds to the beta-amyloid plaques that are notorious in Alzheimer’s disease. This process helps gauge how many plaques have formed in different regions of the brain. With this information, researchers rated the PET scans as positive or negative.
After 36 months, participants underwent the same cognitive exams. The findings revealed that in patients with mild or no cognitive impairment and evidence of plaques at the trial’s start, worsened to a greater degree on cognitive tests than those with negative scans.
In fact, 35 percent of plaque-positive participants who began the study with mild cognitive impairment progressed to Alzheimer’s, compared to 10 percent without plaque. These patients were more than twice as likely to be started on cognitive-enhancing medication than those without plaque.
On the other hand, participants with negative scans experienced much less decline. Ninety percent of participants with mild cognitive impairment, but no plaque did not develop Alzheimer’s. This finding supports the value of using PET imaging to identify patients unlikely to decline, which is important for both clinical research and treatment.
“Having a negative scan could reassure people that they are not likely to be at risk for progression in the near future,” Doraiswamy said.
Doraiswamy said that florbetapir is currently not approved to predict the development of dementia and is not used as a screening tool in cognitively normal people. More research is necessary to fully understand the predictive role of beta-amyloid plaque PET imaging.
“Even though our study suggests the test has predictive value in normal adults, we still need additional evidence,” Doraiswamy said. “We need longer-term studies to look at the consequences of silent brain plaque build-up, given that it affects 15 to 30 percent of normal older people.”
Source: Duke Medicine