By LEE BOWMAN
Scripps Howard News Service
August 30, 2005
Researchers from Leiden University Medical Center in the Netherlands used magnetic resonance imaging to examine the brains of elderly patients with and without dementia related to Alzheimer's or Parkinson's disease, and a control group of healthy young people.
As expected, the images showed that patients with late-onset dementia had more brain damage compared with young adults or seniors with top cognitive function. But they also found that those with dementia had a much lower rate of blood flow than the other two groups.
"Our findings not only support the theory that vascular factors contribute to dementia in the elderly, they are highly suggestive that diminished blood flow indeed causes brain damage," said Dr. Aart Spilt, a radiologist at the medical center and lead author of the study in the September issue of the journal Radiology.
Dementia is a loss of brain functions - such as thinking, remembering and reasoning - that interferes with normal activity. Many conditions produce these symptoms, but Alzheimer's disease is the most common cause, and many Parkinson's patients also develop dementia.
The Alzheimer's Association estimates that some 4 million Americans have the disease today, including about 50 percent of seniors age 85 and older. About 1 million Americans have Parkinson's disease.
While patients with dementia have been shown to require less blood flow to the brain as their brain becomes less active, Spilt said his team's findings offer evidence that the decline in blood flow is a cause of disease, rather than just an effect.
"The findings emphasize the importance of monitoring both high and low blood pressure in older adults," he said. "Possible causes of low cerebral blood flow include heart failure and a narrowing of key arteries."
The study groups included 17 patients who began to experience dementia after age 75 (late-onset) and 16 of the same age with optimal cognitive function, and 15 healthy younger individuals.
The average total blood flow to the brain in the healthy young people was 742 milliliters per minute. In the seniors free of dementia, the rate was 551 ml per minute, while it was an average of 443 ml a minute in those with dementia.
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