Scientists continue to search for genetic answers to why some people live a long time.
One study has now examined more than four hundred fifty people between the ages of ninety-five and one hundred ten. Researchers at the Albert Einstein College of Medicine of Yeshiva University in New York recently reported the latest findings.
The study looked at changes in genes that govern an important cell-signaling pathway. These genes are involved in the action of a hormone that affects almost every kind of cell in the body. The hormone is called insulin-like growth factor, or IGF-one.
Other researchers have found that mutations to the genes cause two effects in animals. The animals do not grow as big as others of their kind but they live longer. The Einstein team wondered if these changes might also influence how long humans live.
So they looked for the mutations in their study group of Ashkenazi, or Eastern European, Jews. Ashkenazi Jews are more genetically similar than most other groups, so any differences are easier to find.
The researchers compared the findings to other Ashkenazi Jews whose family members did not live as long. In the control group, they say, no one had the mutations. Yet even in the study group, where the average age was one hundred, only two percent of the people had them.
In other words, there are more answers waiting to be found. In recent years, the scientists have even identified so-called longevity genes.
The latest findings were published in the Proceedings of the National Academy of Sciences.
The mutations were found mostly in women. Daughters of those who lived to be one hundred had higher levels of the hormone than people in the control group. And they were an average of two and a half centimeters shorter.
A drug that decreases the action of the IGF-one hormone is currently being tested as a cancer treatment. Nir Barzilai, leader of the Einstein study, says the drug could be useful in delaying the effects of aging.
But he noted that the subjects in the study were born with their mutations. So it is not clear whether the drug would help people who receive it later.
Doctor Barzilai also points out that many people are receiving treatments with human growth hormone to try to delay the effects of aging. Yet he says if low growth-hormone action extends life, as the new findings suggest, then he wonders if getting more of it could shorten life.
And that's the VOA Special English Health Report. I'm Steve Ember.