Eunuchs as a Poor Way to Study the Influence of Male Hormones on Aging

A paper that compares genealogical records of Korean eunuchs with their intact peers from past centuries has been doing the rounds, with the data showing a higher life span for the eunuchs. However, there is considerable skepticism from the rest of the research community - there are any number of ways to sneak in a bias towards longer-lived, more robust individuals: how the data came into being; how it is analyzed; how the eunuchs originally came into their position; their life style differences; and so forth.

So it is hard to see any good way to discuss the role of male hormones in relation to this data, given all of the potential confounding factors not addressed by the authors. For example, only 81 of 385 recorded eunuchs had enough information present in the genealogy to pin down a life span. This alone could contain a bias towards longer-lived, more active, or more privileged individuals: there is no reason to think that these 81 are representative. But this is the nature of scientific research - individual research results have to be read skeptically and in the broader context of their field:

Historically, eunuchs have been employed as guards and servants in harems across the Middle East and Asia. The Imperial court of the Korean Chosun Dynasty (1392-1910) also had eunuchs. Eunuchs of the Chosun Dynasty lived with privileges: Korean eunuchs were conferred with official ranks and were legally allowed to marry, a practice that was officially banned in the Chinese Empire. In addition, married couples were also entitled to have children by adopting castrated boys or normal girls. The boys lost their reproductive organs in accidents, or they underwent deliberate castration to gain access to the palace before becoming a teenager. ... Several studies have described the long-term consequences of castration in eunuchs, but there have been no data on the lifespan of eunuchs.

We examined the lifespan of Korean eunuchs by analyzing the Yang-Se-Gye-Bo - a genealogy record of Korean eunuchs. To our knowledge, this is the only record of eunuch-family histories in the world. ... The Yang-Se-Gye-Bo contains the records of 385 eunuchs. From these records, the lifespans of 81 eunuchs could be identified. The average lifespan of this group was 70.0 ± 1.76 years. As lifespan is affected by genetic and socio-economic factors, we compared the lifespan of eunuchs with the lifespan of men from three non-eunuch families of similar social status, who lived during the same time periods. ... The average lifespan of eunuchs [was] 14.4-19.1 years longer than the lifespan of non-castrated men of similar socio-economic status. Our study supports the idea that male sex hormones decrease the lifespan of men.



A further point to be considered is that the Korean eunuchs, as in China, had lost all the make organs. The operation would have been horrific and the incidence of urinary tract infections high. Those eunuchs who survived the operation and its immediate aftermaths would have been a highly selected population with particular resistance characteristics.
This is a well-known confounding factor in such comparative studies.

Posted by: Joc at February 5th, 2013 11:16 PM

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