For a long time, the appendix was considered useless, although it is found in many mammals. In a new study published on 7 July in the Journal of Anatomy, French researchers from Inserm and the Muséum National d’Histoire Naturelle claim that the appendix is associated with increased longevity.
First demonstration of a link between appendixes and longevity
The appendix provides a selective positive benefit for those who have it. This is a far cry from the theories of Charles Darwin, who claimed that the appendix was a rudimentary, useless and functionless structure, and even dangerous, with a risk of inflammation and appendicitis. Numerous studies have examined this organ to better understand its function, but none have reached a definitive conclusion.
In this study, researchers tried to find out what the appendix is good for. To do this, they analyzed data from 258 mammalian species, 39 with and 219 without these appendages. In particular, they looked at theoretical maximum lifespan, i.e. the theoretical lifespan of mammals based on their weight, and the actual maximum lifespan of the different species studied.
A bacterial sanctuary
The results showed that the presence of appendixes correlated with an increase in maximum lifespan. “The idea of looking at lifespan was suggested to us by our work on the relationship between appendicitis/appendectomy, ulcerative colitis, and immune system involvement,” says Eric Ogier-Denis, lead author of the study. With a more active and better trained immune system, we should, in theory, be able to better withstand our environment and live longer. We, therefore, tested this hypothesis in collaboration with two internationally renowned evolution experts from the Muséum National d’Histoire Naturelle. This is the first demonstration of a link between the presence of an appendix and life expectancy.
The researchers believe this link is due to the structure of the appendix. The organ is shaped to form a selective ‘bacterial sanctuary’ that reduces mortality from infectious diarrhea by promoting rapid recolonization of bacterial species important to the host. The presence of appendixes would thus be associated with reduced mortality and therefore increased longevity in mammals that have it.
Appendicitis does not affect lifespan
This does not mean that appendectomy for appendicitis in humans alters life expectancy, explains Éric Ogier-Denis. In fact, appendicitis at a young age is certainly beneficial, as it exacerbates the formation of the immune system and allows it to fight more effectively in the event of a subsequent infection. The treatment of appendicitis remains appendectomy, and this paper provides no evidence to suggest a change in this therapeutic approach. In fact, only appendectomies performed in the absence of appendicitis can have adverse consequences in inflammatory and infectious bowel diseases.
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