Science & Research

Study links hypertension and dementia

High blood pressure can lower oxygen flow to the brain, leading to tissue atrophy, mental decline

By
Senior Staff Writer
Monday, September 15, 2014

High blood pressure — also known as hypertension — may have previously unforeseen implications for the brain that can even cause dementia in some older adults, according to a study published by a team of researchers including several from Brown. 

“Hypertension can lead to vascular narrowing,” said Michael Alosco, a graduate student at Kent State University and lead author of the study. “The arteries become stiff. … They don’t function as they should.”

“This narrowing of vessels results in decreased oxygen flow to the brain, resulting in atrophy and thinning, and therefore can likely increase the risk for dementia,” Gretel Terrero MD’15 wrote in an email to The Herald.

“If you look at brain MRI images of patients with severe dementia, the most classic finding will be significant cortical thinning — even if you are just analyzing the image with your naked eye in the Emergency Room reading room,” she added.

The researchers observed the impact of hypertension on cerebral blood flow and cortical thickness in adults with cardiovascular diseases, Alosco said.

“The number of silent strokes on the MRI scans should be noted because hypertension is known to cause strokes in distributions of small arteries deep within the brain,” Brian Silver, associate professor of neurology, who was not involved with the study, wrote in an email to The Herald.

“These small strokes can lead to severing of connections between different cortical regions, which might account for the reduction in thickness of the cortex,” he added.

The study was made up of 58 older adults with varying cardiovascular diseases, which they self-reported and researchers confirmed with medical records, Alosco added.

The researchers performed MRI tests once without follow-up, and thus gained information about a wide range of patients at a single time point, Alosco said. The results can be found in the August issue of the Journal of the American Society of Hypertension.

But “causation cannot be determined from this study because subjects had a single MRI at one point in time,” Silver wrote.

“To better understand the meaning of this reduced cortical thickness and its relationship with dementia, longitudinal studies should be done,” Terrero wrote. Longitudinal studies include repeated observations of the same test subjects over an extended period of time, Alosco said.

“It would be interesting to see changes over time, for example at one year and two years among the two groups,” Silver wrote.

Future studies can “follow people over two to five years and see how hypertension affects blood flow and brain structure,” Alosco said, adding that this future work is necessary to verify the results of their initial study.

“A solid link between dementia and high blood pressure could lead to changes in current blood pressure guidelines,” Terrero wrote.

“Perhaps we would treat blood pressure sooner,” she added, noting that some doctors do not prioritize treating slightly elevated blood pressure until it reaches a certain level.

Terrero noted that “dementia can be so debilitating, and knowing that potential prevention and/or delay of dementia could be pretty easy” is a reassuring prospect. Patients with high blood pressure can access medication at a palatable cost and without a large risk of other side effects, she added.

“These results point to a potential avenue toward primary prevention of degenerative brain disorders such as Alzheimer’s disease,” Brian Ott, professor of neurology, who was not involved with the study, wrote in an email to The Herald.

Patients can also make lifestyle changes to reduce the risk of hypertension, such as improving diet and increasing exercise, Terrero wrote — these suggestions are her “first line of treatment” when patients arrive at her office seeking treatment for high blood pressure. But while often successful, when these options fail, patients require prescriptions of additional medicine, she wrote.