Call it making the best of a potentially bad situation. Eunuchs -- castrated men -- live nearly 20 years longer than other men, a new study has found.

The study of over 80 eunuchs from the Chosun Dynasty, which ruled in Korea from 1392 to 1897, looked at the world's only known record of eunuchs' lives and compared them to genealogical records of other men of similar social rank. The researchers cross-checked their results with other royal records.

They found that the average lifespan of a Korean eunuch was about 70 years, 14 to 19 years higher than non-castrated men of similar social standing.

Three of the 81 eunuchs lived to be over 100 years old. The researchers calculated that the rate of centenarians among this group of eunuchs was at least 130 times higher than the current rate in developed countries.

"Our study supports the idea that male sex hormones decrease the lifespan of men," said the lead author of the study, Kyung-Jin Min, an associate professor in the Department of Biological Sciences at Inha University in Inchon, South Korea.

This study does not prove that castration directly increases human longevity, said S. Jay Olshansky, a professor of public health at the University of Illinois in Chicago, who studies longevity but was not involved with the study. "It may not have anything to do with being eunuchs," he said, adding that this study did not adjust for lifestyle factors like diet, exercise, and stress.

Previous studies have shown that castration -- which removes the source of male sex hormones -- increases lifespan in animals. But studies in humans haven't been conclusive. One past study found that castrati singers did not live significantly longer than non-castrated singers. Another study has shown that castration increased longevity by 14 years in mentally disabled, institutionalized men. That increase in lifespan is similar to the findings in the Korean eunuch study.

Women reach the age of 110 ten times more often than men, said Dr. L. Stephen Coles, a co-founder of the Los Angeles Gerontology Research Group, who was not involved with the study. In a research group of 67 confirmed centenarians, he said, only three are men.

There may be several reasons for a sex difference in lifespan, experts said.

Females may have an advantage in longevity because they have a back-up X chromosome, Coles said. A women's body is a mixture of cells, half containing an active X chromosome from her mother and the other half from her father, he said. If there is a defect on one X chromosome, half of her cells will be unaffected.

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Eunuchs May Hold Key to Longevity