Dementia and Down Syndrome

Researchers comparing brain changes leading to dementia in people with Down syndrome with those seen in Alzheimer's disease report initial results in a recent issue of Neurology.

Studies indicate 50 percent to 75 percent of all people with Down syndrome will eventually develop signs of dementia, and autopsies show nearly all people with Down syndrome show signs of the brain tangles and plaques commonly associated with Alzheimer's disease -- even when the individual in question did not appear to suffer from dementia while alive. Little research exists to explain the association between Down syndrome and Alzheimer's.

Investigators from the University of California, Irvine, are in the midst of a long-term study to gauge changes in the brains of Down syndrome patients and compare them to changes seen in Alzheimer's patients. The study involves 17 people with Down syndrome who currently show no signs of dementia, 10 people with moderate Alzheimer's, and 24 healthy control subjects. In the initial phase, all underwent positron emission tomography scans to measure glucose metabolic rates in the brain while performing a task involving mental abilities. GMR is known to play a role in dementia.

Results showed lower GMR levels in Down syndrome and Alzheimer's patients when compared to the healthy controls in the posterior cingulate, an area of the brain known to exhibit decreased function in early Alzheimer's. However, GMR was lower in Alzheimer's patients and higher in Down syndrome patients when compared to controls in another brain area related to Alzheimer's -- the temporal cortex.

The investigators plan to continue to follow these patients to see if GMR in the temporal cortex of the Down syndrome patients begins to mimic that seen in the Alzheimer's patients as clinical signs of dementia develop. Ultimately, they hope to find a very early stage at which GMR occurs in the brains of Alzheimer's patients and a way to scan for this occurrence, leading to better treatment for the condition.