Are achy joints the major reason we slow down as we age? Not entirely; blame the brain, too. The part of the brain that controls motion could start a gradual decline at the young age of 40.
New research proposes that in middle age even healthy individuals start to drop parts of the insulation in the motor-control area of the brain. At the same time, their speed starts to faintly slow.
That helps clarify why “it’s hard to be a world-class athlete after 40,” says Dr. George Bartzokis, a neurologist at the University of California, Los Angeles, who led the study.
While this is very unnerving, do not be discouraged. The study shows an additional reason to strive to be physically and mentally fit: An exercised brain could spot deteriorating insulation faster and alert repair cells to fix the problem.
Bartzokis compares the brain to the Internet. High Speed depends on bandwidth, which in the brain is called myelin, a sheet of fat that covers nerve fibers.
Healthy myelin permits quick transmission of the electrical signals the brain uses to send signals. Higher-frequency electrical discharges, called “actional potentials,” increase the speed of the movement, any kind of movement, from a soccer goal to a foot tap.
Think of the basketball great Michael Jordan. “The circuitry that made him a great basketball player was probably myelinated better than most other mortals,” Bartzokis says.
So if myelin builds up in the adolescence period, when does the production decrease so much that we lag in the race to fix fraying, older insulation?
The new research addresses these kinds of questions. First, Bartzokis enlisted 72 healthy men, ages 23 to 80, to execute an easy test: How fast can they tap an index finger? This is a task that anyone can do; it does not rely on power or health.
Researchers tallied how many taps the men created in 10 seconds, noting the two quickest of 10 attempts. Then, brain scans looked for myelin that needed to be repaired in the area of the brain that commands a finger to tap.
Unusually, tapping speed and myelin health both peaked at the age of 39. Then both steadily decreased with mounting age, the researchers said.
That doesn’t entirely mean that the rest of the brain is uniformly affected. Bartzokis has noted that some data indicates that myelin production starts to decline in brain regions accountable for cognitive functions than in motor-control parts.
Going back to his illustration of Jordan, who last played professionally at the age of 40: “Even he started getting older. That circuitry started breaking down a little,” says Bartzokis. “He can become Michael Jordan the big-shot businessman … but not be Michael Jordan the super-duper basketball player anymore.”
Bartzokis’s main goal in conducting the studies is to combat Alzheimer’s disease. Bartzokis’ previous research indicates an Alzheimer’s-linked gene may fight myelin repair.
However, the innovative research has larger repercussions because it provides information on normal aging, says Dr. Zoe Arvanitakis, a neurologist at Chicago’s Rush University Medical Center.
“We knew at some age you peak and there’s a sense it would disintegrate as you grow older. But we didn’t have a sense of where that age would be,” says Arvanitakis.
Bartzokis’ research helps to support a new report from German scientists, that with age comes a deterioration of the system that’s thought to repair broken myelin, adds Dr. Bradley Wise of the National Institute on Aging.
“Any disruption in these neural circuits and networks will have problems for functioning,” says Wise, who says the two reports are creating increased attention into myelin’s part in aging. Of late, most myelin research has placed the majority of attention on multiple sclerosis, where myelin does not slowly dissolve but completely disappears.
The complete study was published last month in the journal The Neurobiology of Aging.
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