The study, published in the journal Current Biology, found castrated men living in Korea centuries ago outlived other men by a significant margin.
Kyung-Jin Min of Inha University in Incheon, South Korea, and colleague Cheol-Koo Lee of Korea University analyzed genealogy records of members of the Imperial court of the Korean Chosun dynasty.
The researchers said they found eunuchs lived 14-19 years longer than other men did. Among the 81 eunuchs they studied, three lived to 100 or more -- a feat of longevity that remains relatively rare even in developed countries today.
The castrated boys in Korea lost their reproductive organs in accidents or underwent castration purposefully to gain early access to the palace. However, eunuchs were allowed to marry and had families by adopting castrated boys or normal girls.
The incidence of centenarians among Korean eunuchs was at least 130 times greater than it is in the developed countries, Lee said, and that can't be explained by living in the palace.
Most eunuchs spent as much time outside the palace as they did inside. Emperors and male members of the royal family had the shortest lives, typically surviving to their mid-40s, Lee added.
"For better health and longevity, stay away from stresses and learn what you can from women," the researchers concluded.