Short of breath? Short chromosomes may be to blame. A new study of elderly twins finds that those with longer DNA than their siblings retained more strength and physical endurance past age 70. Those with the longest chromosomes compared to their twin showed the biggest advantage in self-reported ability to climb stairs, run, and lift weights. Chromosomes shrink naturally with age as cell division chips away tiny DNA fragments from the tips of chromosomes, called telomeres. Genetics may determine telomere lengths at birth, but each person loses DNA at a different rate. Environmental risks such as smoking and stress appear to accelerate the process. Previous studies have linked shorter telomeres with age-related diseases and mortality. The new work, published in an upcoming issue of Mechanisms of Ageing and Development, suggests that telomere length tracks the subtle decline of fitness with age—well before disease strikes. Whether telomere shrinkage causes or merely reflects bodily aging, however, remains a mystery.
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