WASHINGTON: Life expectancy in elderly people is linked to the length of special structures in their DNA, according to a study published on Friday in the British medical journal Lancet. The shorter these structures — called telomeres — the earlier a person died, the report found.

Dr Richard Cawthon of the University of Utah and co-workers analyzed blood DNA samples from 143 men and women age 60 or older. The blood had been drawn for another purpose between 1982 to 1986. At the time of the study, 101 of the people had died.

For each sample, the scientists measured the lengths of the telomeres, which are special protective “caps” that sit at the end of all chromosomes.

The scientists found that overall, older people had shorter telomeres than younger people. This was expected. Prior studies have shown that human telomeres get steadily shorter through life, and some scientists think this could be a key contributor to aging through the malfunctioning of cells.

However, Cawthon and colleagues also compared telomere length between people of similar ages to identify those with shorter — or longer-than-average telomeres for their age.

The scientists found that people whose telomere lengths were in the shortest quarter of the group had a mortality rate from infectious disease eight times higher than those with the longest telomeres. People with telomere lengths in the shorter half had a three-fold higher mortality rate from heart disease.

Overall, women with shorter telomeres died an average of 4.8 years sooner than women with longer telomeres; men with shorter telomeres died four years earlier than those with longer ones.

Elizabeth Blackburn, a molecular biologist and telomere researcher at the University of California, San Francisco, said the study is the first she knows of comparing telomere lengths at specific ages and linking them to mortality.

But she said the study does not necessarily mean that shorter telomere length causes earlier deaths. Cawthon noted that the association is not strong enough to provide a “test” that would allow individual people to know how long they are likely to live. Even if it could, he said, it would be of small use because there is no way to lengthen someone’s telomeres.

“I have never had my telomeres measured,” he said. “The way I look at it, if there’s no treatment, I’m not interested.”—Dawn/The Los Angeles Times News Service.