Scientists found that wild sheep forced to contend with surviving difficult winter conditions tend to be more vulnerable to illness as they get older. The findings suggest that the stress has a long-term effect on their health.
Researchers at the University of Edinburgh found that sheep which had been repeatedly exposed to stressful situations – such as several harsh winters over a lifetime – were worst affected. The study of Soay sheep on the island of St Kilda suggests that persistent or repeated stress has a cumulative effect on long-term health and ageing.
Researchers examined data for a common illness in adult sheep – stomach worms. They found that as the sheep got older, they tended to be more vulnerable to attack from worms.
The study also showed that those sheep which had suffered most stress in their lives aged faster than those sheep which had suffered less stress.
Understanding the effects of stress may help scientists better understand the ageing process.
Adam Hayward, of the University’s School of Biological Sciences, who carried out the study, said: “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.
“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.”
The study, funded by the Biotechnology and Biological Sciences Research Council and the Natural Environment Research Council, was published in the journal Proceedings of the Royal Society B.