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Exercise has been shown to slow cognitive decline in aging, but scientists haven’t known why. Now, by transfusing blood from exercising mice into sedentary ones, researchers have found a single protein, produced in the liver, that seems to underlie restorative effects in the brain.

The discovery is the latest to emerge from scientists’ hot pursuit of treatments to forestall aging, or at least prolong a healthy life span. Previous research on transfusions of “young blood” — plasma from younger blood donors — has captured the public’s imagination, spurring rumors of self-experimentation by aging Silicon Valley entrepreneurs and a government warning last year that such infusions provide no proven health benefit for older adults. The new research suggests it’s not the youthfulness of the blood donor, but their activity level, that might confer a cognitive benefit.


As humans — and mice, and many other animals — age, one of the first symptoms of cognitive decline is the loss of spatial memory. Young brains instinctually guide people to their cars in parking lots. But when car alarms go off as older drivers struggle to find their vehicle, that’s one of the first signs of decline, said Saul Villeda, a University of California, San Francisco, assistant professor and the senior author on the study, published Thursday in Science.

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