By Norbert Herzog and David Niesel
It’s walking into a room then forgetting why you’re there, or failing to remember the name of a known acquaintance.
The loss of memory that comes with older age has been the source of endless embarrassing moments and jokes.
Some view mental decline as an inevitable symptom of getting “over the hill.” Now, a study may have revealed why people experience senior moments, attributing them to brain microbleeds — or BMB — because of stiffening arteries.
Cognitive decline normally begins at about 25 years old, starting with a decrease in numerical abilities as well as arithmetic processing speed. Memory declines can be measured in the late 30s, perhaps as late as the 60s.
Reasoning, verbal ability and visual processing skills begin to decline in the 50s and 60s, although word knowledge, vocabulary and word reading skills remain stable into late adulthood.
The brain requires a great deal of blood, receiving 15 percent of the heart’s output and 20 percent of the blood’s oxygen even though it weighs only 2 percent of the whole body.
However, as people age, the largest blood vessel in the body (the aorta) becomes less flexible, increasing blood pressure in the brain, especially during stress. Pulses of blood can be strong enough to rupture a small blood vessel in the brain, leading to BMB.
BMBs can be found in about 5 percent of healthy adults, 34 percent of people who have had ischemic strokes and 60 percent of people with nontraumatic intracerebral hemorrhages. MRIs show BMBs are small, round centers where blood vessels have burst, causing brain cells to die.
The traditional way of determining blood pressure with an inflatable cuff around the arm measures the local pressure of blood in the arm. But central blood pressure must be measured to determine the stiffness of the aorta.
That’s done through applanation tonometry, where the pressure wave of blood coming from the heart is compared to the reflected pressure of blood vessels farthest from the heart. Aortic stiffness is calculated from the difference in pressure between these two waves.
To determine if central blood pressure and aortic stiffness correlate to a decline in cognitive abilities, researchers measured these in nearly 500 people ranging in age from 20 to 82.
They also subjected the volunteers to a standard battery of tests to measure their cognitive abilities. The results revealed that the higher the central blood pressure and the stiffer the aorta, the worse people performed on tests of visual processing and memory.
To establish that aortic stiffening is responsible for BMBs, these measurements will be repeated on the same volunteers for many years, along with neuroimaging to identify the BMB.
The race is on to develop treatments that could preserve the elasticity of the aorta and prevent BMBs. These results suggest that BMBs may be one more step of the process that leads to mental decline and perhaps dementia.
Professors Norbert Herzog and David Niesel are biomedical scientists at the University of Texas Medical Branch. Learn more at medicaldiscoverynews.com.