Researchers at the Oregon State University in Corvallis linked poorer health and earlier deaths to the absence of a key gene controlling the biological clock regulating the sleep cycle.
The fruit fly study, published in the journal Aging, found the flies without the gene lived just about as long as normal flies -- unless they were subjected to stress.
When the researchers exposed the flies to a mild metabolic stress for 24 hours, they found no change in young flies, but middle-age and older flies showed significant damage beginning to occur.
"We're beginning to identify some of the underlying mechanisms that may help explain why organisms age," Natraj Krishnan said in a statement.
"This study suggests that young individuals may be able to handle certain stresses, but the same insults at an older age cause genetic damage and appear to lead to health problems and earlier death. And it's linked to biological clocks."