We know high blood pressure is not good for the heart. But recent research has shown that high blood pressure is not only bad for the heart, it’s also not good for the brain—and can seriously increase the risk for dementia.
But why does your blood pressure cause cognitive problems? New research shows that the pressure hypertension puts on fragile blood systems in the brain causes a disruption of the delicate balance between blood flow and neuron activity.
According to Dr. Jessica A. Filosa, neurovascular physiologist at Augusta University, high blood pressure can cause cells known as astrocytes, a type of glial cell which monitor neurons, to increase their activity when they usually wouldn’t. And over time, it seems like that may lead to changes in the brain. Scientists still can’t pinpoint the exact time high blood pressure starts to affect cognition, but rogue astrocytes may be a tipping off point.
“Untreated hypertension can lead to cognitive impairment but exactly how it happens, we don’t really know,” said Filosa. “We need to understand the window of change or shift in function in all these different cells. What exactly is happening, in what order and how fast?”
The problem, said Filosa, is that vascular changes that affect dementia risk and brain health happen long before symptoms begin.
“By the time patients are symptomatic, a lot of the physiology of the vasculature has deteriorated so the question is: How can we diagnose impairments in vascular function way before that, years before cognitive impairments are established and become symptomatic?” she said.
High blood pressure makes the tiny arteries that carry blood throughout the brain constrict, meaning less blood is flowing through them. The astrocytes that cover the walls of those vessels are tuned into the added pressure.
Research has shown that the added pressure triggers calcium inside astrocytes, which is a sign that they have experienced an increase in activity. Filosa has theorized that the increase in calcium turns astrocytes, which are normally protective, into bad forces in the brain. They tighten their grip on the blood vessels, increasing constriction and promoting inflammation.
“It can shift who these astrocytes become,” said Filosa.
Researchers said the changed astrocytes do not communicate properly with neurons to signal that they need to use less energy because less blood is available. Over time, this shifts the balance of the brain. Eventually, resting blood flow and neuronal rest is out of whack—and those neurons monitor automated activities like breathing.
To confirm these theories, Filosa is studying how a healthy balance is maintained by looking at pressure changes in human and animal brain slices.
Research shows that high blood pressure raises the risk of stroke, which can increase the risk of dementia by two or three times.
How can you keep your brain and your heart healthy? Experts have repeatedly said that what is good for the heart is good for the brain. A Mediterranean diet has been shown to be both heart- and brain-healthy. And getting 150 minutes of exercise per week has also been shown to have mutual benefits.