After age 39, decline begins

LOS ANGELES, Oct. 20 (UPI) -- After middle age, people start to lose the battle to repair myelin in their brain and motor and cognitive functions begin a long decline, U.S. researchers say.

Dr. George Bartzokis of the University of California, Los Angeles, Semel Institute for Neuroscience and Human Behavior and colleagues compared how quickly a group of males ranging in age from 23 to 80 could perform a motor task and then correlated their performances to their brains' myelin integrity.

In the study, each of the 72 participants had a magnetic resonance imaging scan that measured the myelin integrity in the vulnerable wiring of their brain's frontal lobes. The maximum finger-tapping speed -- the number of taps over a period of 10 seconds -- was measured just before the MRI measure was obtained.

The study, published in the online version of the journal Neurobiology of Aging, supported what the researchers had suspected, that finger-tapping speed and myelin integrity measurements were correlated and "had lifespan trajectories that were virtually indistinguishable" -- both peaked at 39 years of age and declined with an accelerating trajectory thereafter.