A study of eunuchs in Korea's royal court has found men without testicles live longer.

Researchers looking at the court of the Chosun Dynasty found eunuchs lived to 70 on average, or 14 to 19 years longer than "intact" men of similar socio-economic status.

Three of the 81 eunuchs studied lived to 100 or more, giving the group a centenarian rate some 130 times that in developed nations today.

During the dynasty, which ran from 1392 to 1910, boys in Korea sometimes underwent castration in order to serve as eunuchs and gain access to the privileged life of the palace.

Employed through history as guards or servants in harems across the Middle East and Asia, eunuchs in the Chosun court were allowed to marry and had families through adoption.

Kyung-Jin Min of Inha University and Cheol-Koo Lee of Korea University believe the longevity of the eunuchs was not simply attributable to their privileged lifestyle.

"Except for a few eunuchs, most lived outside the palace and spent time inside the palace only when they were on duty," Min told Reuters.

In contrast, the average lifespan of the kings, who spent their whole lives inside the palace, was just 47 years.

Previous studies have shown female mammals generally live longer than males, and one explanation is that testosterone weakens the immune system and can increase the chances of heart disease.

Scientists have also found that castration typically prolongs lifespan in animals but studies on people have been inconclusive.

While data on mentally ill, institutionalized men showed them living longer, the lifespan of castrato singers was not significantly different from their non-castrated counterparts.

The study was published in the journal Current Biology.

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