According to U.S. scientists how well you respond to stress predicts how long you will live, at least if you are a worm.
The scientists from the University of Colorado at Boulder, found that genetically identical worms responded to stress in greatly different ways.
They say that the worms with more active stress reactions lived much longer than worms with less active stress proteins.
Apparently more active stress responses suggest the animal is coping with the stress.
They suggest their findings will almost certainly apply to humans in some respect.
Researcher Shane Rea tested more than 100,000 nematodes known as Caenorhabditis elegans, a worm favored by scientists because it is easy to work with.
Caenorhabditis elegans despite its tiny size, is genetically complex and has much in common with "higher" animals such as humans.
The team genetically engineered the little transparent worms to carry a jellyfish gene called green fluorescent protein, which glows green under certain light.
This gene was then tagged to a gene called hsp-16.2, a stress protein found in most organisms, that is associated with the health of cells.
The more active the hsp-16.2 gene was, the brighter the worms glowed green and, presumably, the better they coped with stress.
In a typical experiment, the research showed that, under identical conditions, the worms that glowed the brightest green lived about 16 days, compared to three days for those that glowed the most weakly.
Professor Thomas Johnson, who helped lead the study, says they have shown it is possible to predict the life span in an organism, on the first day of adult life, based on how it responds to stress, and this has not been done before.
Johnson says the findings have implications for human longevity and health.