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Comment by mullingitover | Hacker News Reader

It's gonna be, at least in part, vaccines[1]. If we invented drugs today that did what routine vaccinations did for Alzheimer's prevention, it would be hailed as a medical miracle.

> Patients who received the Tdap/Td vaccine were 30% less likely than their unvaccinated peers to develop Alzheimer’s disease (7.2% of vaccinated patients versus 10.2% of unvaccinated patients developed the disease). Similarly, HZ vaccination was associated with a 25% reduced risk of developing Alzheimer’s disease (8.1% of vaccinated patients versus 10.7% of unvaccinated patients). For the pneumococcal vaccine, there was an associated 27% reduced risk of developing the disease (7.92% of vaccinated patients versus 10.9% of unvaccinated patients).

[1] https://www.uth.edu/news/story/several-vaccines-associated-w...

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Random thought. Do antibiotics kill any sort of permanent seemingly benign outside bacteria in the body? Did we historically have more ongoing internal invaders than we do now because we now have antibiotics? I guess I'm asking did we used to have persistent, ongoing infections that now get wiped out every so often as a side effect of taking antibiotics?

Not just antibiotics to consider along this line of thought. We historically had a higher load of parasites. Far more of the population had some amount of parasites more of the time. Things like sewer systems/sanitation/clean drinking water/bathing and personal hygiene/wearing shoes/not having piles of animal feces all over the streets. That all changed the amount of exposure to parasites for the common person. We know it affected our immune systems (overall rates of allergies increased). We do not know how it affected our brains. Makes intuitive sense that it must apply to bacteria as well. Before foods were pasteurized (and before refrigeration), for example, we were exposed to more dietary sources for bacteria, both beneficial and non-beneficial.

Sometimes. Not reliably. I've seen studies correlating antibiotic therapy with reduced dementia rates in the next 5 or 10 years or something, but you can just as well wipe your gut microbiome and open it up to opportunistic pathogens.

I am actually very interested to see the data play out with the first generation of people who received the chickenpox vaccine as kids (millennials). If you have chickenpox, then you're at risk for shingles later in life, which seems to be a contributing factor to dementia in some individuals. But if an entire generation isn't at risk of shingles, we would probably expect to see a statistically significant drop in dementia as well.

>I am actually very interested to see the data play out with the first generation of people who received the chickenpox vaccine as kids (millennials).

Excuse me?

The vast majority of millennials did not receive the chicken pox vaccine as it was not FDA approved until 1995. The youngest millennials were born in 1996. The oldest millennials were already in high school by 1995.

I guess I could be wrong here - I know that myself and several other friends got it as kids once it was released. It was given to us later than many of our other vaccines.

>I guess I could be wrong here

The only people in the US who have received an immunization for chicken pox were those who were NOT exposed to the chicken pox virus prior to 1995 (the first year it was available).

Before immunizations almost everyone got chicken pox in the first few years of life.

Thus the majority of people born between 1981 and 1996 were exposed to the chicken pox virus before 1995 and weren't eligible for immunization.

I was born in the early 80s and got chicken pox in 1993. It was considered very late at the time, everyone was like "wow, how have you not had chicken pox before?"

There was an interesting article along those lines: The brain microbiome: could understanding it help prevent dementia? https://www.theguardian.com/lifeandstyle/2024/dec/01/the-bra...

That’s super interesting! From the first line I thought this comment was going to go the other way, lol…

Still hard to draw conclusions. It could be that people who get all the recommended vaccines are just in general more health-conscious and this has some relationship to dementia risk.

> could be that people who get all the recommended vaccines are just in general more health-conscious and this has some relationship to dementia risk

Huh, it looks deeper than mere correlation [1][2].

The simple explanation is inflammation. The intriguing potential is the vaccines train the immune system to clear something harmful.

EDIT: It looks like some HSV antibodies also attack various Alzheimer's-related compounds, including "Aß protein, tau protein, presenilin, rabaptin-5, β-NGF, BDNF, mTG, and enteric nerve" [3]. Wild. I wonder if there is a link between the vaccination status of a mother and childhood dementia presentation.

[1] https://www.nature.com/articles/s41591-024-03201-5

[2] https://pubmed.ncbi.nlm.nih.gov/33856020/

[3] https://pmc.ncbi.nlm.nih.gov/articles/PMC6032666/

The shingles vaccine is another promising one[1]

> Researchers found that compared to those who didn't get the shingles vaccination, those who received it...

> were 3.5% less likely to develop dementia over seven years (a 20% reduction)

These types of findings are problematic for anti-vaxxers, however they seem likely to overcome this through their wholesale butchery of US research.

[1] https://www.health.harvard.edu/blog/can-a-routine-vaccine-pr...

I think it's going to be very interesting to see what kind of effects long term antiretrovirals for HIV treatment and prevention have. Surely they're not so tightly targeted that they only affect HIV, so it'll be interesting to see which conditions they prevent and which they cause, since we've got tons of people on them for a quarter century now or so.

I also wonder this kind of thing about other long term treatments - perhaps Prozac prevents dementia, or causes it.

The interesting thing about dementia is that it is not normally distributed whatsoever. Pick basically any characteristic imaginable - environmental, behavioral, or genetic, and you're going to find a difference, often very significant, between groups.

Everything from your occupation, to your diet, to martial status, to hobbies, and much more have been shown to have significant relationships with dementia rates. The problem you obviously run into here is that a person's approach towards healthcare is itself a major behavioral characteristic and so seeing varying rates of dementia based on this characteristic alone would be very unsurprising.

> seeing varying rates of dementia based on this characteristic alone would be very unsurprising

Sure. That's why the antibody cross-reactivity is intriguing.

You're begging the question. While endless things are associated with dementia (or its absence) nobody knows what causes it, and so looking for causal reasons with behavioral characteristics is going to mislead without carefully controlled experimental (and not observational) studies.

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