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Brain insult from hypertension discovered in middle-aged adults

But some brains reorganize for better communication after injury from hypertension

CHICAGO --- Hypertension that leads to vascular dementia in older adults begins to impact the brain by middle age, reports a large new Northwestern Medicine study, the first to show the process begins so early. But in some middle-aged individuals with this damage, their brains reorganize to bypass the damage and enhance communication between brain cells, the study also found. And these people did better on tasks related to cognitive function. 

“This tells us some people’s brains appear to compensate by rerouting communication in the brain networks to improve messaging. It’s like creating detours when one route is blocked or clogged,” said lead study author Dr. Farzaneh Sorond, professor of neurology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine neurologist. “If we can develop a treatment to produce this plasticity in an older person’s brain, we might be able to improve their cognition and mobility.” 

Sorond is also the Dean Richard H. Young and Ellen Stearns Young Professor at Northwestern.

The study was published this week in the journal PNAS (Proceedings of the National Academy of Sciences.

Not everyone is affected equally by damage to their brain’s white matter as they age, Sorond said. 

“Why is that?” Sorond said. “We’ve been asking that for decades. Here we have an important clue. These people with white matter disease in their brain, why are they functioning OK? If we can figure it out, then we can help others.”

In the multi-site study, scientists observed 600 individuals, average age of 55.5 in an fMRI. All had vascular risk factors and at risk for vascular dementia in late life but currently had normal cognitive function. Scientists looked at the executive function region of their brains, which is one of the first regions affected as people develop age-related white matter injury. This region of the brain is key to working memory and controls planning and decision making. 

One form of brain injury from hypertension appears as white splotches, referred to as white matter hyperintensities, on brain MRIs.

While participants were resting in the fMRI, scientists measured the level of oxygenation across the entire brain. As the brain works, it increases and decreases oxygen in a synchronized manner. The synchronization was enhanced in the people whose brains had redistributed paths to the brain’s executive function region and were able to compensate for the white matter injury. 

“The increased synchronization in the brain means communication is improved,” said first author Lisanne Jenkins, research assistant professor in psychiatry and behavioral sciences at Northwestern.

Next, the participants were given a series of tasks that tested their executive function. Those individuals whose brains had shown increased connectivity and rerouted brain networks performed better on the tasks than those whose brains did not.

The study adjusted for diabetes, cholesterol, BMI (Body Mass Index) and smoking, so scientists only were looking at the effect of blood pressure.

Other Northwestern authors are Alexandr Kogan, Carson Ingo, Sanaz Sedaghat, Todd B. Parrish, Alexander J. Nemeth, Dr. Donald M. Lloyd-Jones and Lei Wang.

This study was supported by the National Institute of Neurological Disorders and Stroke grant R01-NS085002. The CARDIA study is conducted and supported by awards from the National Heart, Lung, and Blood Institute (NHLBI) in collaboration with the University of Alabama at Birmingham HHSN268201800005I and HHSN268201800007I, HHSN268201800003I and HHSN268201800006I and the Kaiser Foundation Research Institute HHSN268201800004I. CARDIA was also partially supported by the Intramural Research Program of the National Institute on Aging (NIA) and an intra-agency agreement between the NIA and the NHLBI AG0005.