Poor Brain Blood Flow Raises Dementia Risk

TUESDAY, Aug. 30, 2005 (HealthDay News) -- Reduced blood flow to the brain may help spur dementia in the elderly, Dutch researchers report.

They believe that a chronic drop in cerebral blood pressure -- resulting in declines in the delivery of oxygen and glucose vital to brain functioning -- causes brain damage that can trigger the onset of dementia, whether it be linked to Alzheimer's disease or other causes.

"I think it's surprising, but we see more and more evidence for the fact that blood flow is more important in the developing of dementia in older men and women than was previously thought," said study author Dr. Aart Spilt, of the department of radiology at Leiden University Medical Center in the Netherlands. His team reports their findings in the September issue of Radiology.

According to the National Institutes of Health (NIH), dementia refers to a broad range of intellectual impairments involving memory, problem-solving, emotional control and the overall ability to think and reason.

Dementia is not considered to be a disease in itself, but rather a collection of symptoms brought on by diseases such as Alzheimer's and, in some cases, Parkinson's. Intellectual impairment of this sort is not considered to be a normal part of aging, despite its common occurrence among the elderly.

In their study, Spilt and his colleagues focused on a group of 17 elderly Dutch patients all diagnosed with Alzheimer's-related dementia.

The male and female patients were all over the age of 75 and diagnosed with so-called "late-onset dementia." All underwent blood testing and neuropsychological exams. Researchers also used MRI to look for signs of structural brain damage and impairments in brain blood flow.

Results were compared with similar tests conducted among a group of 16 elderly men and women of similar age without dementia. A third group of 15 healthy young men and women (averaging 29 years of age) was also tested.

As expected, the researchers found that the younger group had greater brain blood flow and less evidence of brain damage or scarring than either of the older groups.

When looking solely at the elderly patients, however, those suffering from dementia demonstrated significantly greater structural brain damage and significantly lower brain blood flow than the healthy patients.

As measured in milliliters (mL), the dementia patients had an average cerebral blood flow of 443 mL per minute --108 mL per minute lower than the healthy elderly group.

Based on these findings, the Dutch team say late-onset dementia shows clear associations with both structural brain damage and decreased cerebral blood flow.

Impaired brain blood flow can result from heart failure or other cardiovascular problems such as a narrowing of either brain or neck arteries due to atherosclerosis.

"So we think the most important point is that besides hypertension -- which is very important to regulate -- its also important to look at hypotension [low blood pressure], to see if elderly people with low blood pressure are at risk for dementia," Spilt said.

He stressed although elderly patients often demonstrate reduced blood flow as a result of diminishing brain activity, the normal aging process does not account for the striking differences observed in blood flow between the healthy elderly patients and the dementia patients.

Ideally, future studies could follow up on this finding by tracking healthy patients over a one- to five-year period, watching to see how blood flow changes correlated to the development of dementia over time, Spilt said.

Dr. David Yousem, director of the department of neuroradiology at Johns Hopkins University in Baltimore, expressed confidence in the study conclusions.

"Basically, there has been a debate about the degree to which blood flow to the brain contributes to the onset and severity of dementia," he noted. "And this study strongly suggests that blood flow is one of the components that has to be factored in when a patient develops dementia -- be it Alzheimer's or other dementias."

"So this finding points out that we have to be very cognizant of the state of our cardiovascular system as we get older," Yousem added. "Not only for the health of your heart, but for the health of your brain."

More information

For more on dementia, check out the National Institute of Neurological Disorders and Stroke.