5 ms·

This is a fluff piece. We've known for decades that the thymus is an important part of the immune system. It's not an organ that's been believed to be vestigial

This is a fluff piece. We've known for decades that the thymus is an important part of the immune system. It's not an organ that's been believed to be vestigial, like the appendix. > For the study, Kooshesh mined data from 1,146 adult patients who had undergone thymus removal, alongside demographically matched control patients who had undergone similar surgeries but kept their thymus Sure, you can demographically match all you want, but I don't think this is a research question that can be answered with a retrospective analysis. The problem is that you haven't controlled for why surgeons decided to remove the thymus in some cases and not in others. Was the disease more severe in patients who got thymectomies? Was it differences in training between the surgeons? Was it just an arbitrary decision on the part of the surgeons? This is a critical confounder regardless of whether you've matched the demographics. You really need a randomized control study to answer this sort of question. > Although the risk of autoimmune disease did not differ substantially between the groups in the overall primary cohort (relative risk, 1.1; 95% CI, 0.8 to 1.4), a difference was found when patients with preoperative infection, cancer, or autoimmune disease were excluded from the analysis (12.3% vs. 7.9%; relative risk, 1.5; 95% CI, 1.02 to 2.2) What? What is this? Was this subgroup analysis preregistered, or did they just go fishing when their primary hypothesis didn't pan out? I'd categorize this study as mildly interesting, but not groundbreaking the way the press statement is selling it.

mlyle 3y ago
This is a research question you can't answer with a prospective analysis either, because it's not ethical in most cases to randomize whether you're removing a body part. The best we're going to do is a careful case control study (and research in animal models). And the evidence is enough to imply strongly that we should expend a little more effort to avoid removing the thymus.
- Calavar 3y ago
  > This is a research question you can't answer with a prospective analysis either, because it's not ethical to randomize whether you're removing a body part. But that's exactly what we did with the appendix, multiple times [1, 2]. [1] https://pubmed.ncbi.nlm.nih.gov/26080338/ https://pubmed.ncbi.nlm.nih.gov/26080338/ [2] https://www.nejm.org/doi/full/10.1056/nejmoa2014320 https://www.nejm.org/doi/full/10.1056/nejmoa2014320
  - mlyle 3y ago
    I had thought about this and had amended this to "in most cases" before you posted. If the standard of care is removing the appendix, and you have a strong reason to believe that something less may be superior, you may be able to conduct a randomized trial. But any other combination of facts is going to be hard for an IRB to swallow.
jjtheblunt 3y ago
Isn't the universally known T cell named with a T because of the thymus which imparts their programming? Like known for decades?
- anon84873628 3y ago
  Yes, but some believed this function was most relevant in adolescence, with the importance fading in adulthood. The purpose of the research is to understand the role of the organ in later age.
- readthenotes1 3y ago
  More now, since I was a part of the other universe that didn't know this!
anon84873628 3y ago
Well, if the study had found no significant correlation, that would have been interesting information. I'll still applaud the researchers on this one.
joe__f 3y ago
I believe that the appendix is now understood to be a store for gut flora so that the microbiome can regrow after an infection or bad episode of diarrhoea etc.
- bookmark1231 3y ago
  It’s been conjectured by some researchers that maybe this is the case, particularly for infants. But there’s very little evidence for it. As far as I’m aware there have been no studies that are able to statistically distinguish between people with and without an appendix in terms of actual heath outcomes
  - delfinom 3y ago
    Otoh, I wouldn't say that dismisses the appendix having a potential role. Part of the problem is we barely have a grasp on gut flora and it's full impact on human health, and several studies show that impact can be over years including potentially being one cause of dementia.
- runnerup 3y ago
  I believe it’s only posited to be useful for isolated small groups where everyone might get the same stomach bug at the same time, and have no other humans around with a healthy gut biome to “re-infect” them. Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us.
  - hn_throwaway_99 3y ago
    > Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us. Do you have any citations for that? Perhaps it differs by city and region, but many modern cities with good sanitation systems are exceptionally clean - you're not getting frequently reinfected by others' gut flora unless there is a catastrophic problem with the sewer system. People with things like C. difficile infection can have chronic disease for years, and fecal transplants have only recently been recognized as a good treatment in those cases - point being you have to have an actual fecal transplant, you're not just going to "get reinfected with healthy microbiome from sharing germs with all the other humans".
contravariant 3y ago
I take it a relative risk of 1 is a null result? If so a confidence interval of 1.02 to 2.2 after arbitrarily excluding some data is not exactly ground breaking.
- nerdponx 3y ago
  It's suggestive of p-hacking. "Look, the bottom of the interval is just above 1! Finally I can publish this."
outworlder 3y ago
> It's not an organ that's been believed to be vestigial, like the appendix. Not vestigial evolutionary speaking, but doesn't it get less and less functional over a person's lifespan and gets replaced with fat tissue?
- echelon 3y ago
  Yes. This is why T cell activity decreases as one ages. The thymus is where naive T cells are generated, and the output dramatically slows after adolescence.
Brajeshwar 3y ago
Recently, while on my usual documentaries watch, I learnt that the appendix may no longer be considered appendix. From Wikipedia[1], “The appendix was once considered a vestigial organ, but this view has changed since the early 2000s. Research suggests that the appendix may serve an important purpose as a reservoir for beneficial gut bacteria.” 1. https://en.wikipedia.org/wiki/Appendix_(anatomy) https://en.wikipedia.org/wiki/Appendix_(anatomy)

mlyle 3y ago

This is a research question you can't answer with a prospective analysis either, because it's not ethical in most cases to randomize whether you're removing a body part. The best we're going to do is a careful case control study (and research in animal models). And the evidence is enough to imply strongly that we should expend a little more effort to avoid removing the thymus.

Calavar 3y ago
> This is a research question you can't answer with a prospective analysis either, because it's not ethical to randomize whether you're removing a body part. But that's exactly what we did with the appendix, multiple times [1, 2]. [1] https://pubmed.ncbi.nlm.nih.gov/26080338/ https://pubmed.ncbi.nlm.nih.gov/26080338/ [2] https://www.nejm.org/doi/full/10.1056/nejmoa2014320 https://www.nejm.org/doi/full/10.1056/nejmoa2014320
- mlyle 3y ago
  I had thought about this and had amended this to "in most cases" before you posted. If the standard of care is removing the appendix, and you have a strong reason to believe that something less may be superior, you may be able to conduct a randomized trial. But any other combination of facts is going to be hard for an IRB to swallow.

jjtheblunt 3y ago

Isn't the universally known T cell named with a T because of the thymus which imparts their programming? Like known for decades?

anon84873628 3y ago
Yes, but some believed this function was most relevant in adolescence, with the importance fading in adulthood. The purpose of the research is to understand the role of the organ in later age.
readthenotes1 3y ago
More now, since I was a part of the other universe that didn't know this!

anon84873628 3y ago

Well, if the study had found no significant correlation, that would have been interesting information. I'll still applaud the researchers on this one.

joe__f 3y ago

I believe that the appendix is now understood to be a store for gut flora so that the microbiome can regrow after an infection or bad episode of diarrhoea etc.

bookmark1231 3y ago
It’s been conjectured by some researchers that maybe this is the case, particularly for infants. But there’s very little evidence for it. As far as I’m aware there have been no studies that are able to statistically distinguish between people with and without an appendix in terms of actual heath outcomes
- delfinom 3y ago
  Otoh, I wouldn't say that dismisses the appendix having a potential role. Part of the problem is we barely have a grasp on gut flora and it's full impact on human health, and several studies show that impact can be over years including potentially being one cause of dementia.
runnerup 3y ago
I believe it’s only posited to be useful for isolated small groups where everyone might get the same stomach bug at the same time, and have no other humans around with a healthy gut biome to “re-infect” them. Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us.
- hn_throwaway_99 3y ago
  > Which explains why in dense modern society we couldn’t find a difference that the appendix makes, because we get reinfected with healthy microbiome from sharing germs with all the other humans in our big cities - some of whom didn’t just get a terrible stomach bug at the same time as us. Do you have any citations for that? Perhaps it differs by city and region, but many modern cities with good sanitation systems are exceptionally clean - you're not getting frequently reinfected by others' gut flora unless there is a catastrophic problem with the sewer system. People with things like C. difficile infection can have chronic disease for years, and fecal transplants have only recently been recognized as a good treatment in those cases - point being you have to have an actual fecal transplant, you're not just going to "get reinfected with healthy microbiome from sharing germs with all the other humans".

contravariant 3y ago

I take it a relative risk of 1 is a null result? If so a confidence interval of 1.02 to 2.2 after arbitrarily excluding some data is not exactly ground breaking.

nerdponx 3y ago
It's suggestive of p-hacking. "Look, the bottom of the interval is just above 1! Finally I can publish this."

outworlder 3y ago

> It's not an organ that's been believed to be vestigial, like the appendix. Not vestigial evolutionary speaking, but doesn't it get less and less functional over a person's lifespan and gets replaced with fat tissue?

echelon 3y ago
Yes. This is why T cell activity decreases as one ages. The thymus is where naive T cells are generated, and the output dramatically slows after adolescence.

Brajeshwar 3y ago

Recently, while on my usual documentaries watch, I learnt that the appendix may no longer be considered appendix. From Wikipedia[1], “The appendix was once considered a vestigial organ, but this view has changed since the early 2000s. Research suggests that the appendix may serve an important purpose as a reservoir for beneficial gut bacteria.” 1. https://en.wikipedia.org/wiki/Appendix_(anatomy) https://en.wikipedia.org/wiki/Appendix_(anatomy)