High blood pressure may heighten the effects of Alzheimer's disease

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Using arterial spin-labeled MRI, scientists have discovered that hypertension, or high blood pressure, reduces blood flow in the brains of adults with Alzheimer's disease, according to a new study presented at the 93rd annual meeting of the Radiological Society of North America (RSNA) this week in Chicago.

"While hypertension is not a cause of Alzheimer's disease, our study shows that it is another hit on the brain that increases its vulnerability to the effects of the disease," said study co-author Cyrus Raji, MD and PhD candidate at the University of Pittsburgh in Pennsylvania.

For the purpose of the study, Raji and his colleagues at the university used arterial spin-labeled MRI, a non-invasive way to measure blood flow in the brain without an external contrast agent, to image 68 elderly adults.

The patient group included 48 normal individuals, including 38 with hypertension and 10 without; 20 Alzheimer's patients, including 10 with hypertension and 10 without; and 20 adults with mild cognitive impairment, 10 with hypertension and 10 without. Mild cognitive impairment, which affects brain functions such as language, attention and reasoning, is a transition stage between normal aging deficits in the brain and greater levels of dementia.

According to the results “rCBF is substantially decreased in patients with HTN compared to those without in CN, AD, and MCI groups. Overall rCBF is lowest in AD with HTN (34.8 ml/100g/min) compared to CN with HTN (41.43) and MCI with HTN (47.75). Most notably decreased flow in AD occurs in the posterior cingulate (35.9), prefrontal cortex (29.5), and the thalamus (28.9).”

The MRI results showed that in all patient groups blood flow in the brain was substantially decreased in patients with hypertension compared to those without. Cerebral blood flow was lowest among the Alzheimer's patients with hypertension, but the normal group with hypertension showed significantly lower cerebral blood flow than the normal group without hypertension.

"These results suggest that by changing blood flow to the brain, hypertension—treated or untreated—may contribute to the pathology of Alzheimer's," Raji said.