Scientists who analysed genealogy records of eunuchs of the Korean imperial court dating from 1392 to 1910 have claimed that castration can increase lifespan by up to two decades
The records included information about eunuchs, who either lost their reproductive organs in accidents or underwent castration to gain early access to the palace.
The noble Korean eunuchs lived 14 to 19 years longer than men of similar social class who were "intact".
Among 81 eunuchs studied, three lived to 100 or more. The average eunuch lifespan was 70, compared with 60 to 56 for non-eunuch men in the court.
Centenarians were at least 130 times more common among the Korean eunuchs than they are in developed countries today, said the researchers.
The finding suggests that male sex hormones, produced in the testes, may be responsible for shortening men's lives.
In Europe men live an average of 78 years and women 82.
"This discovery adds an important clue for understanding why there is a difference in the expected lifespan between men and women," said lead scientist Dr Kyung-Jin Min, from Inha University in Korea.
Eunuchs have historically been employed as guards and servants in harems across Asia.
In the latest research, the longevity of eunuchs was compared with that of men from non-eunuch families of similar social status in the court of the Korean Chosun Dynasty. The scientists discounted the theory that palace life contributed to the eunuchs' long lives. Most of the eunuchs lived outside the palace and only visited it when on duty.
Kings and male members of the Korean royal family, who spent all their time in the palace, had among the shortest lifespans of all, surviving only to their mid-40s.