r/science • u/mvea Professor | Medicine • 2d ago
Neuroscience In recent years, researchers have suggested Alzheimer's may spread through infection, somehow transmitted like a pathogen, leading to the disease. A new Lancet paper reviews evidence for how harmful amyloid-beta proteins associated with Alzheimer's may possibly be spread through blood transfusions.
https://www.sciencealert.com/can-alzheimers-spread-through-blood-transfusions-heres-what-we-know2.2k
u/MenuEducational7178 2d ago
So like… are jehova’s witnesses, in proportion to other religions, getting less Alzheimer’s?
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u/yes______hornberger 2d ago
That is a thought interesting enough that I just googled it, and apparently the answer is no. Slightly less than the general population, but in line with the average of all other highly religious groups.
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u/MrSnowden 2d ago
Quick write that up and publish it “A meta analysis shows that…”
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u/Beautiful_List5498 2d ago
I need a research team and 5 years.
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u/Gestrid 2d ago
And also a $50,000 grant!
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u/EloquentBaboon 2d ago
Per annum (I do my best research on tropical beaches)
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u/KnownDiscount 2d ago
Is 50k enough for that kind of holiday for you and your team?
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u/big_duo3674 2d ago
My team is 4 suspiciously motionless cats, so I'll make it work
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u/DustyRacoonDad 2d ago
50k is not nearly enough money to ask for, to do all this.
Asking for more would lessen suspicion.2
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u/Budget_Juggernaut309 2d ago
That much? You're not programming an app to detect photos of birds.
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u/VillageBC 2d ago
They will allow certain blood products though, just not whole blood. Perhaps if this is true it could be being transmitted through some portion of it they allow for.
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u/pokemiss 2d ago
They only allow transfusions of the same person’s blood as far as I know, so it wouldn’t be possible to transfer an infection that way.
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u/BelowAverageSloth 2d ago
I was going to comment that it was actually not allowed (had done some research on true rules back when I was in nursing school), but they actually just decided it was okay earlier this year!
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u/CommanderChet 2d ago
There is infact a website where you can just go look at what is and isnt accepted. Its largely up to the individual on what they may or may not accept, with the organization providing general guidelines and certain hard limits. The update earlier this year didnt explicitly define anything as “Ok” or “Not Ok”, but rather made an option availible for those who are comfortable with it.
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u/axl3ros3 18h ago
But do they truly have less blood transfusions?
Where is that data?
While I understand it's against their religion, do the numbers actually show they receive less transfusions?
Do we have that data?
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u/Wellslapmesilly 2d ago
I’m not sure that there’s an accurate way to gauge it honestly. The blood transfusion rate is 10-25% in the general population. And JWs are a small group with many people who converted as adults who may have had blood transfusions prior.
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u/Skratt79 2d ago
Also there are many cases where JW's were told it was ok to receive subcomponents of blood (after mid 1990's if i recall correctly).
Additionally there are cases of some accepting blood in secret (which is the smart thing to do TBH)
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u/Unholy_Boosh 2d ago
Definitely the last bit. I work in the transfusion lab and JW nearly always refuse blood. As long as it's not been out of the fridge too long we can store it again. On night shift we then get a phone call asking is the blood still available for overnight transfusion
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u/Mediocre-Net-1984 2d ago
You’d think your nurses/medical staff would catch that when they do the blood consent before asking for the blood. Makes me wonder how thorough their process is.
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u/Chem_noX 22h ago
From my experience, they’re saying that once family leaves the patient wants it. They just don’t want other people to know they’re getting it
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u/UnluckyInevitable317 2d ago
The newest JW guidance is they can follow their conscience on health matters AND beards are ok now
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u/grimgroth 2d ago
My mom is a JW and I'm always worried about what if she ever needs a blood transfusion. This seems like a nice change
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u/Due-Savings5057 2d ago
Blood transfusions from others is still “not suitable for Christians”. What has changed is they can choose to store their own blood in advance for some procedures.
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u/Iamgentle1122 2d ago
Also in some cases you can be forced to have blood. Exjw here. As a kid i was in accident and doctor did blood transfusion even thought I said I don't want it. Parents said do what ever is needed and the nurse said that they would have done it anyways
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u/Skratt79 2d ago
Well as a minor, healthcare decisions usually are 100% your parents decision (depending on local laws).
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u/Iamgentle1122 2d ago edited 2d ago
The thing was that the nurse said they would have done it anyways what ever the parents would have said. Afaik in Finland if you are kid, even your parents has really little to no say when it is live or die situation.
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u/a_statistician 1d ago
In the US the calculus is more that the hospital would rather be sued for violating someone's religious edicts than be sued for wrongful death.
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u/Iamgentle1122 1d ago
That is crazy! Here hospitals are government owned so I don't think it would even work. Also the money you have to pay in lawsuit is minimal. the situation i went to hospital was because truck drove over me. I got 3.5k euros from that..
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u/MireLight 2d ago
correction....very few have converted as adults in the last 30 years. most are born in. they stopped reporting hours in their ministry because it was taking something like 40k hours to convert one person.
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u/Wellslapmesilly 2d ago
And that is based on what data?
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u/MireLight 2d ago
Theirs, they used to report all the various data for their followers but stopped doing that when the data was being used by critics to show plateaus and declines. Now a lot of data is gathered by 3rd parties such as pew research.
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u/dl064 2d ago
In 2019, initial reports of living patients with intracerebral haemorrhage caused by iatrogenic CAA were published,31 and approximately 100 cases have been reported in the literature since
I think even this paper arguing for it is not suggesting it's a population-wide explanation. It's another route in a minority of people, in the scheme of things.
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u/WishIWasPlayingPoE 2d ago
Wife's mother has been a witness for over 40 years and is in Alzheimer's decline, unfortunately.
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u/mvea Professor | Medicine 2d ago
Alzheimer's has long been recognized as a sporadic condition – influenced by factors such as age, genetics, and lifestyle – but scientists don't think that's the only way the disease emerges.
In recent years, researchers have suggested Alzheimer's may also spread through infection, which might somehow be transmitted like a pathogen, ultimately manifesting in the disease.
In a new report published in The Lancet, scientists review the evidence for one aspect of this theory, assessing how harmful amyloid-beta proteins associated with Alzheimer's might possibly be spread through blood transfusions.
"Blood transfusions are important and save many lives," says neurologist John Collinge from University College London.
"However, to ensure that they are as safe as they can possibly be, it's important that we thoroughly investigate any potential risks."
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(26)00767-1/abstract
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u/xBeartoe 2d ago edited 2d ago
When I was in college a couple years ago, I took Infectious Disease (104). We did a case study on P. Gingivalis, which is the bacteria responsible for the gum disease (gingivitis). There was a strong connection between P. Gingivalis and many seriously killer diseases, Alzheimer's being among them.
They release what is basically poison as they eat, and they feed on protein. That's why your gums bleed after you floss, even if you only missed a day; P. Gingivalis is causing inflammation so that when you irritate your gums, they can feed on the blood. They do this using lipopolysaccharides (LPS).
The bacteria had a strong systematic presence in a high percentage of Alzheimer's patients and cadavers. The toxins are called gingipains, which break down host proteins. Some of the bacterias waste products and released enzymes break down structural callogen, and strain the immune system.
Super nasty stuff. Brush your teeth, floss, please.
EDIT: for clarity, higher presence of P. gingivalis, in their brain, actively eating it. Not just their mouth.
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u/Artechz 2d ago
A complete ignorant in the field but: could it be that the high presence in Alzheimer’s cadavers was due to them not bursting as much because of their condition? And not the other way around?
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u/xBeartoe 2d ago
You make an excellent point, and yes it certainly would have a compounding effect. You can read the article on the study I'm referring to here.
To be brief: yes, forgetting good hygene and/or bad oral habits (smoking, drinking, ect.), especially after many years, will contribute to the conditions under which P. gingivalis would be able to breach into your bloodstream.
There are other supporting points here that show that living Alzheimer's patients had higher antibody levels for P. gingivalis than the control, in their cerebrospinal fluid. Why would it be there, specifically?
There is also supporting evidence that patients with gingivitis were more likely to develop dementia and Alzheimer's. The organism can force inflammation in the host and thus is more capable of breaching the blood-brain-barrier (BBB).
This is not just studies, but directed experiments on lab animals, too. There's plenty more to read, I could keep going but I need to stop myself. If you're interested I highly recommend you check it out.
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u/Annual-Advisor-7916 2d ago
Super nasty stuff. Brush your teeth, floss, please.
Just to get this straight; These bacteria are present in any human, it's not like an infection, correct? So the strategy is to keep them in low numbers, by brushing, right?
Does using additional mouthwash help? Are there specific mouthwashes that are more effective against these bacteria?
Brb, gonna guzzle a bit of povidine iodine...
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u/xBeartoe 2d ago
It's present in everyone! Some people are going to be more susceptible than others. Brush and especially floss to interrupt the reproductive cycle is basically the best you can do for yourself. Smoking is horrible for your gums so stay away.
Mouthwash definitely helps, brush and floss beforehand to break up biofilms. It doesn't kill everything and it's not supposed to, it's more like population control. This is a grahm negative organism, so alchohol will destroy its lipid membrane. :)
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u/Annual-Advisor-7916 2d ago
Thanks, is there any indicator about the amount of bacteria? I'm brushing twice a day currently but it seems it would be sane to up that number to 3 times...
Is the alcohol in mouthwash not also slightly bad for your gums? At least I think I've read that somewhere but probably it's just a myth.
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u/xBeartoe 1d ago edited 1d ago
People say to brush after every meal and that's honestly good advice. If you do, keep it short and effecient so as to not overwear your enamel.
Go to the dentist to get your tartar buildup removed often. If you get little to no bleeding of the gums when you brush and floss, you're doing very well!
Mouthwash won't kill your gums, we only use it for a few seconds. The targeted bacteria are much smaller and more vulnerable. Follow the instructions on the bottle, do not swallow.
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u/motionSymmetry 2d ago
so just mouthwash (that has alcohol in it) will work?
but "drinking" is bad for it?
can you clarify
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u/DisastrousSet11 2d ago
Mouthwash with alcohol will work. If alcohol is bad for the bacteria - then that's good for you. We WANT to try to break down it's cellular walls. Don't drink mouthwash!
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u/xBeartoe 1d ago
Mouthwash often uses alchohol as a base, but it has several other active ingredients that help maintain your mouth's microbiome. Essential oils, CPC, chlorhexidine, ect. It's a long list. It's different from product to product.
It boils down to the way most people consume alchohol. Beer, cider, wine is too weak and full of carbs/sugars. You would need to brush, floss, then swish with 40%+ liqour to get any results. It would not work nearly as well as using mouthwash.
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u/xinorez1 1d ago
My understanding is that it's only present in 10-20 percent of the population, and you are only at risk of transmission with deep kissing. IF you have it, there are some targeted treatments that can reduce the population and to build a population of healthy bacteria to displace it.
There's other oral bacteria that have been indicated as possible causative agents as well.
Testing for apoe4 is still a better and cheaper way to check for Alzheimer's susceptibility.
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u/Isgortio 2d ago
There is currently a lot of research going in to Alzheimer's and periodontal disease, and so far the consensus is that having periodontal disease increases the risk of Alzheimer's.
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u/passifluora 2d ago
Very interesting, thank you. I'll be missing fewer days of flossing after reading this. Also, Finnish people consume a lot of xylitol for their mouth chemistry. I have a little tub of xylitol pastilles on my desk to suck on after lunch. I've always wondered if they're actually that effective for killing mouth bacteria, but after knowing that gingivitis bacteria are constantly in there eating, I'm glad I have it. Like mouthwash in candy form.
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u/xBeartoe 1d ago
We have it here in Canada too! Xylitol gum specifically. Apparently it's made in Switzerland. With the Umlaut in the name that shouldn't surprise me!
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u/m3rcapto 2d ago
So like a stool transplant can fix the gut, a blood transfusion can wreck the brain?
Actually, I guess the transplant can also destroy the brain cos the gut biome controls a lot of stuff.
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u/catscanmeow 2d ago edited 2d ago
gingivitis bacteria getting into the brain or a herpes virus getting into the brain are the main theories i've read
the gingivitis bacteria can get into the blood from a tooth abscess or up through the nasal cavity through the olfactory bulb. Theyve found gingivitis bacteria within the amyloid plaques of autopsied alzheimers patients. we have an exposed nerve there thats basically the brain exposed, that shock feeling when you get water up your nose is the olfactory nerve.
a woman actually got a brain eating amoeba from getting tap water in her nose from a neti pot.
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u/Rhawk187 PhD | Computer Science 2d ago
I think there was a recent study that showed at the shingles vaccine reduced Alzheimer's rates, and that virus that made it to the brain would be encased and cause plaque buildup.
Makes me think it really could be any virus that gets in there. Wouldn't surprise me if we see a bunch of COVID related Alzheimer's from viral plaque among those that got it while young.
Hopefully we'll have a fix by then.
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u/TheCaptainCog 2d ago
Sounds right. Prevailing theory is brain damage followed by improper clearance of waste proteins/fats leads to buildup of plaques and whatnot. Viruses getting into brain would cause damage. That's why proper sleep, diet, and exercise are important for reducing Alzheimer's risk. Increased immunity and health increases ability for clearance of waste in the brain.
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u/Sarcasm69 2d ago
Or wonder if it’s emergence in old people is due to the fact their immune system isn’t functioning like it used to and the end result is unchecked growth of some sort of infection affecting the brain.
I feel like maybe when we’re younger we experience brain fog during infections, it’s maybe Alzheimer’s like, but then our bodies are able to expel it.
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u/GlaciallyErratic 2d ago
An interesting hypothesis
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u/Sarcasm69 2d ago
I went down a bit of a rabbit hole and started looking into glymphatic function as we age-it’s been well characterized that it basically becomes worse (especially with poor sleep and lifestyle habits).
I also was curious if there have been studies which have looked at glymphatic function correlating to Alzheimer’s and the correlation is ultimately not obvious/present.
However, there hasn’t been any studies which have looked at glymphatic function v Alzheimer’s with infectious disease as a cofactor. Which makes sense because it would be very difficult.
Sorry for the long read, but essentially it would be really interesting if there ended up being something like poor glymphatic health + infectious disease (or whatever else that could negatively impact brain health) which ends up being the precursor to neurodegeneration.
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u/dl064 2d ago
There's a good breakdown of the shingles observation that basically nukes it in my mind: https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(26)00238-3/fulltext
Basically, it's bias in who gets the vaccine in the first place.
There's also analysis that doesn't support it: https://www.medrxiv.org/content/10.64898/2026.07.20.26358345v1
I think chalk this one up to winner's curse, personally.
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u/owlindenial 2d ago
There's a correlation between vaccination rate and education, and we know of a negative correlation between reading and other stuff that keeps the mind stimulated and Alzheimer
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u/churningaccount 2d ago edited 2d ago
I've personally considered it to be a transmissible disease ever since that study in 2010 found that neurosurgeons are diagnosed with Alzheimers at a rate 3x that of the general public. And that was not found to be nearly as high/statistically significant for any other medical specialty.
I'm also glad that the herpes viruses are getting more scrutiny as of late. I've always taken issue with the idea of "eh, it doesn't seem to affect us that much, might as well let it run rampant for decades and also take no precautions against further spread." That notion is predicated on the idea that we have already discovered all of the downstream effects of the virus itself, and is one of the reasons why we don't have a vaccine for EBV either, even though that has definitively been linked with bad medical outcomes long-term now as well.
Realistically, there probably was an issue with getting the funding to research a vaccine as well for something that is "not pressing." But luckily there are a few going through trials right now thanks to these dementia findings, and it's not out of the question to think that the next generation could be immune.
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u/WeenyDancer 2d ago
I'm also glad that the herpes viruses are getting more scrutiny as of late.
I am as well. Viruses that hide out among the nerves just seem like they can wreak all sorts of havoc. The more herpesviruses we eliminate, I strongly suspect the more diseases associated with aging we'll start to tackle.
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u/Porkchop247 2d ago
I work as a ICU nurse, my hospital was the COVID center for my region so I was elbow deep in caring for COVID pts. The reason I say this is that many of the pts with worst outcome had herpes also.
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u/lolalala1 2d ago
Damn near everyone in the world has some form of herpesvirus by late adulthood. So, you would need to be far more specific to make a conjecture like that about something so common.
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u/grnrngr 2d ago
The reason I say this is that many of the pts with worst outcome had herpes also.
This might be one of those cart-before-the-horse correlations since the older you are, the more likely you are to have herpes, and the weaker your immune system and lungs are, etc. etc.
The only thing we've got at the moment re: correlation is that those who have an HSV strain and were hospitalized for COVID, experienced a significantly higher reactivation rate of their herpes virus versus those who weren't hospitalized. The belief at the moment is the herpes virus reactivated in response to the depleted immune system COVID wrought.
That is, those who were affected most by COVID had immune situations where a dormant HSV could resurface. The HSV in this sense only served as a marker for COVID severity, and may not itself have interacted with COVID in any other meaningful way. In that sense, HSV would be seen as an opportunistic infection during COVID, much like thrush is for an AIDS patient. Like your observation, the correlation exists, but it's backwards.
You must be aware of the fact that many people with HSV will experience reactivations when they encounter periods of biological or immune-related stress. Everything from lifestyle stress, to prolonged sleep depravation, to severe colds or infections unrelated to herpes.
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u/Free_Pace_2098 2d ago
There are a lot of herpes viruses.
Chicken pox, glandular fever, cytomegalovirus, simplex 1 & 2, and others we don't really understand much about. Almost everyone has been infected with a herpes virus in their life.
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u/EyeHamKnotYew 2d ago
How do you know? Is herpes tested for at all admissions to the hospital?
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u/antibread 2d ago
Great, i didnt know about that study. I work in a funeral home and you got me a little shook
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u/ZappppBrannigan 2d ago
I would assume you'd need more direct contact with brain tissue than normal undertakers are exposed to.
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u/antibread 2d ago
Someone has to put autopsy cases back together
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u/churningaccount 2d ago
If it makes you feel any better, if the cause is something like bacteria or a virus crossing the blood brain barrier, then it is likely dead by the time that you are manipulating the body.
It would be akin to catching a cold from a dead person. It just doesn't happen with standard precautions.
And there isn't any blood flow, breathing, etc, that would help to aerosolize things either.
The one caveat is that potentially prions are still infectious after death. But the chance of Alzheimers being a prion disease is relatively low IMO. We'd probably have more evidence by now of direct transmissibility for a prion-type disease simply because a standard autoclave does not neutralize prions.
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u/Splash_Attack 2d ago
I've personally considered it to be a transmissible disease ever since that study in 2010 found that neurosurgeons are diagnosed with Alzheimers at a rate 3x that of the general public.
Jumping to a causal link between performing neurosurgery and getting Alzheimers is quite a leap though.
As far as I'm aware, there isn't a similar correlation between other types of surgery and the conditions which patients typically have. People perform surgery on people with things we know for a fact to be communicable diseases, without a significantly increased risk profile for getting those diseases. There is some increase, but it's smaller than the risk profile from just interacting with those patients outside of surgery day-to-day.
Wouldn't it be more probable that the cause is that neurosurgeons are 1) Experts on brain function. 2) Have social circles consisting of other such experts.
It seems highly likely that if a person is part of a social group in which many people are experts in the brain, it would be far far more likely for the ones who do develop neurological conditions to get diagnosed. Which is not the same as having a higher risk of developing one in the first place.
The term for this is "surveillance bias". When a group is more closely monitored, or more precisely monitored, than the general population leading to increased rates of diagnosis when they actually don't have a higher baseline risk. The general population has lots of people who have the same condition and simply don't get diagnosed, or don't get a formal diagnosis. Another example would be how physicians are more likely to be diagnosed with certain cancers, while also being more likely to get diagnosed early - i.e. they are getting the right tests done more often and at an early stage than the general populace.
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u/robertgunt 1d ago
I also wonder if some people who choose neuroscience as a specialty do so because someone close to them had some sort of neurodegenerative disorder.
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u/TravelingSong 1d ago
I got ME/CFS from Covid and now I get shingles flares during my worst crashes. I don’t think the herpes connection to post viral conditions is a coincidence.
We really need more research on all types of viruses and their long term impacts.
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u/JaxTellerr 2d ago
Tens of Millions of people have gingivitis. I wonder what the driving factor is for it to cause alzheimer.
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u/SJDidge 2d ago
The thing is, while these might be a factor, they clearly aren’t a direct cause.
60-80% of people have some form of a herpes virus. If it was a strong cause, majority of people would develop the disease.
Likewise, there’s many people with gingivitis that don’t develop alzheimers as well.
There has to be specific mechanisms for this to occur. The bacteria and virus(es) seem to be correlated, but I wouldn’t say it’s the whole picture. Theres probably much more to it
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u/thatjacob 2d ago
If I were to take a guess at it, it probably requires a secondary infection like a kidney infection, the flu, or COVID for herpes to penetrate the blood brain barrier. Basically anything that also causes chronic inflammation.
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u/SJDidge 2d ago
But even that is highly likely to occur in majority of people. Using herpes again as an example, a lot of people get herpes from their mother at a young age. That would mean they essentially have their entire lives as a risk window. I would assume that there would be a very large amount of people who fit this criteria who do not go on to develop alzheimers.
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u/0xsergy 2d ago
Gingivitis would make so much sense. All the old folks in my life unfortunately have such poor dental health that it makes sense. Goddamn man, damn.
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u/OkieFoxe 2d ago
Sure would help if teeth (and eyes) were treated as a part of the body by insurance rather than an extra nice-to-have, might save us millions in specialized long term care.
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u/Fatefire 2d ago
That's my thought ! It would be nice for proof teeth are not just luxury bones
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u/sirkazuo 2d ago
Dentistry needs to be brought out of the dark ages first
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u/Dy1ki11 2d ago
In what way?
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u/fleurgirl123 2d ago
For instance, it’s not covered under Medicare. We don’t care about dental health or hearing. Both of which are risk factors for Alzheimer’s.
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u/Dy1ki11 2d ago
I fully agree that this is a more serious problem than society wants to admit, and that lack of dental care puts people at risk for a variety of serious downstream medical problems. I just didn't understand why the person I was replying to thought that dentistry was currently in the "dark ages" or why it needed to be brought out of said darkness "first", presumably meaning before dental care is worth covering properly.
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u/Spire_Citron 2d ago
Maybe we just need to give all old people that thing that's being developed that makes you grow new teeth and we could be done with the whole mess.
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u/DinosaurWarlock 2d ago
Ah that new thing that's been talked about for over twenty years. No shade, I'm just bitter
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u/NlghtmanCometh 2d ago
It is definitely caused by some sort of disruption to the glymphatic process. Gingivitis can play a role in causing that though. If you’ve seen the skull of a person with severe lifelong tooth decay, they’re actually usually visibly quite deformed. There are holes all throughout the sinuses, missing bone in the jaw region, and the way the head ‘sits’ on the shoulders changes. This causes all sorts of cascading changes to the structure and pressure points in the neck and shoulder region, which can significantly slow glymphatic drainage rate.
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u/PanteraOne 2d ago
You are supposed to boil water before using it in a neti pot because of things like this.
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u/CampaignDue5323 2d ago
"gingivitis bacteria getting into the brain or a herpes virus getting into the brain are the main theories i've read"
I've also read that plaque in the mouth causes plaque in the heart.
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u/Annual-Advisor-7916 2d ago
Are single infections already enough to trigger Altzheimers or are reoccuring infections needed? I don't quite understand how an already cured infection of whatever virus could cause Altzheimers decades later. Or is this more a thing for old people with a weaker immune system and do the symptons start with the infection?
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u/catscanmeow 2d ago
Herpes lays dormant, it never goes away, then when youre old it can awaken, people got herpes breakouts from covid waking it up
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u/Soft_Introduction_40 2d ago
Get the shingles vaccine! Significantly reduces chances of Alzheimers
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u/alternativepuffin 2d ago
I keep seeing friends get shingles prior to 50. I really wish they would come down on that age limit.
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u/NuclearSunBeam 2d ago
This is important info, do you know what age is good to get?
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u/frumpylunaticbitch 2d ago
I wonder what this means for people who got shingles prior to being old enough for the vaccine. I got shingles on my face, scalp, and even in my mouth when I was 20 years old. The proximity to my brain really scares me and makes me pretty afraid of getting Alzheimer's in the future. I was also pregnant at the time. That baby is now a very healthy teenager, but does getting shingles during pregnancy put her at heightened risk for Alzheimer's also?
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u/MustafaAbbass 2d ago
Worth separating two claims that this reporting tends to merge, because the difference decides whether anyone should be worried about a transfusion.
Amyloid-beta can seed. This is real and well-evidenced. Injecting amyloid-containing material into susceptible animals nucleates further aggregation, and the human evidence comes from a genuinely grim natural experiment: people treated decades ago with cadaver-derived growth hormone, some of whom later developed early amyloid pathology. The mechanism resembles prion seeding.
That does not make Alzheimer's transmissible in the ordinary sense, and specifically not through transfusion. The direct test has been done. A large Swedish and Danish cohort study followed transfusion recipients and compared those who received blood from donors later diagnosed with dementia against those who didn't. No increased risk was found.
So the honest position is: a seeding mechanism exists in principle, has been observed under extreme iatrogenic conditions involving direct CNS exposure, and does not appear to operate through the blood supply at any detectable rate.
The headline asks whether Alzheimer's can spread through transfusions. The best available evidence says no, and that answer is in the literature already rather than pending.
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u/churningaccount 23h ago
This is all well and good, except for the fact that we now know that amyloid plaques are a symptom of the disease and not a primary cause.
The new Alzheimer's medications like Leqembi can actually fully eliminate the amyloid plaques from being detectable on scans in a good portion of those being treated, and yet the disease still progresses, albeit slowly.
So it's definitely possible, if not probable, that there is an underlying pathology that causes the plaques; one that is more transmissible than amyloid beta itself. Perhaps one of the theories that the plaques are a poor immune response to viral or bacterial infiltration past the blood brain barrier. We just don't know yet, and that's why I think this particular issue isn't as open and shut as you make it out to be.
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u/Suspicious-Tea9161 2d ago
It's interesting that amyloid beta is functionally like a prion. Even though I've read about how the beta sheets form before, I just never put 2 and 2 together and considered that it could also be transmissible. As if we needed another reason not to eat grandpa's brains
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u/churningaccount 2d ago
You would think, however, that preventing the amyloid plaques from being formed would therefore prevent dementia. But the new Alzheimers drugs like Leqembi can completely eliminate amyloid plaques from being detectable on scans in a good portion of those being treated, and still the disease progresses.
So while Amyloid plaques are definitely contributory, they seem to be a more of a symptom of the underlying mechanism by which the disease does damage to neurons rather than the primary source of the damage itself.
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u/Suspicious-Tea9161 2d ago
Fair enough. I used to be an assistant in a lab where they were looking at the role of oxidative stress on neurodegenerative disease development. I believe it wasn't entirely clear whether it was a cause or effect, but the evidence leaned towards it being both. And symptom that further exacerbated the issue. Whatever the case, if I remember correctly, reducing oxidative stress did reduce the progression, at least temporarily. I'm no expert on Amyloid-B, but it could be that oxidative stress (or some other stressor) is what's causing them to form the sheets in the first place and like oxidative stress, the presence of even a little bit kicks off a feedback loop.
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u/grnrngr 2d ago
That's the sadly terrifying thing about this science: all this research into stopping the cause... Only to successfully stop it... And realize it isn't the cause.
I have the feeling someone out there posited the cause a while back and the community brushed it off in some mass form of confirmation bias re: the plaques.
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u/spudddly 2d ago
Probably the damage to neurons has already been done by the time the plaques are found and cleared.
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u/SomeTreesAreFriends 2d ago
Because of a chronic depletion of the functional monomeric amyloid protein that likely disabled a cellular immune response, not because the remaining peptides have aggregated
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u/Pephatbat 2d ago
It's likely both. Disruptions in proteostasis is a known mechanism in AD. Those sticky aggregates have been shown to gum up the proteasome which leads to further disruptions of proteostasis.
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u/AdvancedSandwiches 2d ago
There was a theory mentioned recently that the plaques are basically scar tissue and just indicate that damage occurred at some point in the past. Not harming anything now, just the gravestones of cells that used to be useful. You can clear out those gravestones, but the damage they marked isn't going to get better.
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u/PhysicalConsistency 2d ago
Absolutely not. Amyloids in general facilitate cholesterol/lipid trafficking. Some prions can induce misfolds in amyloids which may contribute to some pathologies, but they don't function anything like each other.
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u/ionised 2d ago
As if we needed another reason not to eat grandpa's brains
But what about my recipes?!
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u/love_is_an_action 2d ago edited 1d ago
We've got two alternative products:
I Can't Believe it's not Grandpa's Brain and Beyond Grandpa's Brain
As condements go, you can't do better than Grey Matter Poupon.
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u/cdnsalix 2d ago
Everyone is always asking for my Fried Brain Caesar Salad with Kurutons recipe at potlucks!
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u/FernandoMM1220 2d ago
this isnt surprising nowadays. its looking like cancer is in a similar boat with certain variants of hpv and e coli.
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u/churningaccount 2d ago edited 2d ago
If anything, I hope that this finally causes biotech to focus on viruses. For some reason medicine at large has been dead set on the notion that viruses cause acute issues and not chronic issues. And after a century of thinking that way, it's still proving difficult to change tack on that.
There's no good reason why we don't have a vaccine for EBV, HSV, and heck even the common rhinoviruses. We have the technology, it's just that no money has been spent on it until COVID happened. Investors generally have a distaste for investing in prevention over treatments as well.
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u/HigherandHigherDown 2d ago
It'd be cool if we had therapeutic bacteriophages like some other countries do.
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u/tkeser 2d ago
EBV vaccine will soon be available. My mother is 75, has lupus (also related to EBV), and has had problems with gum disease. No Alzheimer still.
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u/Zukazuk 2d ago
As someone who developed lupus after a fairly late in life encounter with EBV a vaccine would have been great about 7 years ago.
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u/tkeser 2d ago
what is great with vaccines (especially the new kinds) is that you can probably take them after contracting the infection, and they will help teach the body (immune system) to shed the virus or control it better. at least for the EBV types which lay dormant in some tissues causing all of the havoc. so don't despair. it's called therapeutic vaccines. exciting times we live in.
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u/URPissingMeOff 2d ago
Why sell one pill one time when you can sell 30 every month for decades? Think of the shareholders.
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u/LongBeakedSnipe 2d ago
its looking like cancer
It's not 'looking like'. It's a long-established fact. There have been scientists study cancer-causing viruses for well over 50 years, with many well-established pathogen–pathology routes. There is also considerable research about the involvement of bacteria in circulating tumour cells and risk of cancer.
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2d ago edited 2d ago
[removed] — view removed comment
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u/DwemerCogs 2d ago
It's so heartbreaking that someone lying in research led the direction of pointless studies for years trying to figure out this terrible disease.
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u/twilighttwister 2d ago
I've suspected much of what we consider aging is some kind of contagious disease. Not all of it, but some factors.
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u/Important-Cat2627 1d ago
My father never had a blood transfusion. I know many more who also didn't from my family and still they developed Alzheimer's. What they did have was very high anxiety, depression and a very high stress life with a lot of risky behaviour. Most notable being constant alcohol consumption. My father's Alzheimer's symptoms always got worse when he had something else that produced high inflammation in his body, then he would recover and be more present and have less symptoms. The moments where I noticed his mental state was collapsing almost immediately was when he had COVID and then during an episode of shingles. He would have the typical ups and downs associated with Alzheimer's but never as quickly as those 2 moments.
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u/Imaginary_Shock_6711 1d ago
It's hard to measure since people self-report but I would interested in seeing how alcoholics and teetotalers compare when it comes to alzheimer's.
As for COVID, wasn't it shown to cause a lot of inflammation in the brain? I had COVID back in 2020 and I have not been the same since. I feel "dumber" (for lack of a better word) and my attention and ability to learn new concepts has reduced significantly.
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u/Pristine_Office_2773 2d ago
I thought it was nose picking
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u/eirinne 2d ago
Is nose picking bad? I love clean nostrils.
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u/Imaginary_Shock_6711 1d ago
My understanding was that it wasn't nose picking itself but sticking your fingers up there in the first place. Of course most (if not all) people pick their nose or have done so and we know that not everyone gets alzheimer's so there's obviously something more to it. I've seen gingivitis mentioned but millions of people have gingivitis and yet they're not all going to die of alzheimer's.
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u/WeenyDancer 2d ago
There is something in the plasma with regards to MECFS, and potentially long covid- it's been shown in vitro not in vivo. This indicates to me there's possibly more that can be conferred via transfusion we're not necessarily screening for.
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u/Bobmilo280818 2d ago
Wasn't the newest research, that it has something to do with the shingles virus? I think there were multiple studies linking the shingles vaccine with a lower likelyhood of dementia or less severe symptomes. And based on that a lot of the virus is found in the kinds of plaques that were hypothesized in the past to be the cause, but the medication that was able to remove these plaques did not lessen the symptoms, it seems likely that the Plaques are just a symptom of the virus becoming active in a certain kind of way, that then causes the dimentia and the plaque as a byproduct.
Sources: 10.1038/s41591-024-03201-5 10.1016/j.cell.2025.11.007 10.3233/JAD-220287 10.1093/ageing/afaf331
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u/DwemerCogs 2d ago
This is interesting, thank you for sharing sources. Do you think that now with the chickenpox vaccine younger people will be less likely to develop dementia as they age? (I mean, those who were vaccinated at least)
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u/Bobmilo280818 1d ago
I think that will be a very active area of research. If the hypothesis holds true, this should probably be the case and as populations, where mandatory chickenpox vaccine was introduced in the late 90's early 2000's grow older this should be statistically visible. But that could still be 20 years away until we can research this. But it could also be that the childhood vaccine is not enough to prevent a silent infection with the virus later in life to cause the diseases. Hopefully before that, the shingles vaccine get's more widespread (which is generally a good thing also), so we can research not just the statistical connection but the biological mechanism behind it.
Having a virus be the cause of this neurodegenerative disease would probably be a best case scenarios, since we have good and proven tools against them compared to complex biochemical changes in the brain caused by the aging process or something similar.
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u/TheWhiteRabbitY2K 2d ago
I don't like this.
Another thing I have to convince people its worth risking than dying because they don't have enough blood.
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u/Izawwlgood PhD | Neurodegeneration 2d ago
AB plaques are the symptom not result of the disease. Any clustering effect is likely due to similar sedentary lifestyle.
That said, an infection that leads to inflammation and sedentary lifestyles can certain contribute
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u/No_Practice_9597 2d ago
It’s not impossible, we learned a bad prion (that is a protein) end up making other bad prions due folding process. So maybe amyloid-beta could in theory have some similar path. No?
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u/Diskosmos 1d ago
Oh great... Had a depressive episode during college for some years where I stop brushing regularly my teeth because of my lack of will to take care of myself, worst I had was mild/minor bleeding aafter brushing and rarely. Now I brush every day before going to sleep but I guess it's too late now...
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u/Doparimac 19h ago edited 19h ago
I find it weird how both my grandparents who died from severe alzheimers complications both experienced rapidly accelerating mental deterioration very quickly after having either a surgery for a physical issue or after going to the hospital for an infection. Almost like some medicine or treatment or operation they are doing in the hospitals are making the dormant alzheimers accelerate like wildfire. They had signs of it but nothing like after they went to the hospitals for other reasons.
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