Researchers at Imperial College London and the University of Oulu, Finland studied DNA samples from 5,620 men and women born in Finland in 1966. (Agencies)
They measured structures called telomeres, which lie at the ends of chromosomes and protect the genetic code from being degraded.
Telomeres become shorter over a person's lifetime, and their length is considered a marker for biological ageing. Short telomeres are linked to higher risk of age-related diseases such as type 2 diabetes and heart disease.
The researchers looked at telomere length in blood cells from samples collected in 1997, when the participants were all 31 years old.
The study found that men who had been unemployed for more than two of the preceding three years were more than twice as likely to have short telomeres compared to men who were continuously employed.
The analysis accounted for other social, biological and behavioural factors that could have affected the result, helping to rule out the possibility that short telomeres were linked to medical conditions that prevented participants from working.
This trend was not seen in women, which may be because fewer women than men in the study were unemployed for long periods in their 30s, researchers said.
Whether long-term unemployment is more harmful for men than women later in life needs to be addressed in future studies, they said.
"Shorter telomeres are linked to higher risk of various age-related diseases and earlier death," said Dr Jessica Buxton, from the Department of Medicine at Imperial College London.
"Stressful life experiences in childhood and adulthood have previously been linked to accelerated telomere shortening. We have now shown that long-term unemployment may cause premature ageing too," Buxton said.
Researchers at Imperial College London and the University of Oulu, Finland studied DNA samples from 5,620 men and women born in Finland in 1966.