Youth is a wonderful thing,” George Bernard Shaw once said. “What a crime to waste it on children.” Humor aside, recent research suggests that youthful energy may not be “wasted” after all. Through social interactions alone, the young can pass some of their vigor on to the elderly, improving the older generation’s cognitive abilities and vascular health and even increasing their life span.
Although researchers have documented these benefits in mammals, such as rats, guinea pigs and nonhuman primates, the reason for the effect has remained unclear. Now biologist Chun-Fang Wu of the University of Iowa offers a genetic explanation in the May 27 issue of the Proceedings of the National Academy of Sciences. Wu and graduate student Hongyu Ruan found that the presence of youthful, active fruit flies doubled the life span of a group of flies with a mutation in Sod1, a gene that has been linked in humans to Alzheimer’s disease and amyotrophic lateral sclerosis (ALS), a motor-neuron disorder also known as Lou Gehrig’s disease.
Fruit flies are quite social, Wu explains; social cues govern both their reproduction and aging process. And their genes are easier to manipulate than those of their mammalian counterparts—by altering Sod1, Wu created flies that died after only about two weeks, a quarter of their normal life span. When housed with younger flies, however, the Sod1 mutants lived for about 30 days. The mutant flies also became more physically fit, according to heat-stress tests and other measures, when housed with the younger “helpers.” Clipping the younger flies’ wings significantly reduced the positive effects on the mutants’ life span, suggesting that physical activity plays a key role in the life-extending mechanism.
Physical activity is well known to benefit elderly humans, but working out in a social setting with younger people seems to be especially valuable. Sharon Arkin, a psychiatrist at the University of Arizona, runs a clinical program in which Alzheimer’s patients engage in communal exercise sessions with college students. She showed that her program stabilizes cognitive decline and improves patients’ moods.
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