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Comment by quanto | Hacker News Reader

> the latest work addresses one of the biggest criticisms of the microbial theory of Alzheimer’s: HSV-1’s ubiquity. Alzheimer’s impacts only about 10% of the population — if HSV-1 were causing it, why are there so many people who are repositories of the virus but not developing the disease?

That's the rub. Even if this non-traditional brain model is to be taken at face value, there is a missing variable somewhere, arguably more important; HSV-1, at best, would be a contributing factor.

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I know right. If polio causes paralysis then why do only 0.5% of people who contract polio become paralyzed? Checkmate.

That is mixing up necessary versus sufficient. If all people who develop Alzheimer’s contracted HSV-1 prior to developing Alzheimer’s and all people who did not contract HSV-1 do not develop Alzheimer’s (technically implied by my first statement), then you can make a good case for causality. Obviously you can do better, but that is a good start.

> That's the rub. Even if this non-traditional brain model is to be taken at face value, there is a missing variable somewhere, arguably more important; HSV-1, at best, would be a contributing factor.

Did you completely miss the point of the article and even of the quote you copied. "the latest work addresses [this very criticism you have]"?

The article tells us what the missing link is (according to their hypothesis). That's the whole point of it. It's even in the title.

> Research suggests concussions could awaken latent infections in the brain and lead to dementia

That'd be the suggested missing link, physical impact disturbing dormant virions in the brain or allowing a temporary passage to a part of the brain they're normally unable to reach.

There was a study published in 2022 suggesting that there's a link between Epstein-Barr and Multiple Sclerosis (where the immune system attacks the neuron insulation layer), and that when you get infected affects the outcome. Cleverly, they used blood samples from US service members, who have to do it multiple times in life.

https://www.science.org/doi/pdf/10.1126/science.abj8222?src=... [PDF]

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