A new study on a flock of island sheep says a lifetime of stress can quicken the aging process.
Researchers at Edinburgh University, who studied sheep under different conditions, claim that the finding could help understand the aging process in humans.
To reach the conclusion, boffins studied 650 Soay sheep in Village Bay on the archipelago's main island of Hirta.
After analyses, researchers found that sheep living in harsh winter conditions tend to be more vulnerable to illness as they get older, suggesting that continuous stress has an effect on long-term health.
The animals were also scanned for a common illness of stomach worms existing in adult sheep, and found that as the sheep got older they became vulnerable to attack from worms.
The researchers learnt that sheep that had suffered most stress in their lives aged faster and found it harder to reproduce or survive than those sheep, which had suffered less stress.
"As we get older, our health tends to decline, but in addition to this, environmental factors make us age. Our age in terms of years may not correspond to the body's true age," Scotsman quoted Adam Hayward, of the university's School of Biological Sciences, who carried out the study, as saying.
The scientist claimed that a man aged 50 might be healthier than another of the same age depending upon how stressful their lives have been.
Relating the statement to the study conducted, he said: "In the case of the Soay sheep, exposure to stress may have an irreparable effect on their health. Persistent stress may weaken their immune system, making them age faster than sheep which experienced less stress."