Let’s get one thing absolutely clear: no one knows what causes Alzheimer’s disease! Yes, we have heard a lot about amyloid beta (Aβ) plaque accumulating in the brains of patients. Drug companies have invested billions trying to develop anti-amyloid drugs. But the results have been less than impressive. There is no cure for this devastating disease. And while most researchers state unequivocally that you can’t catch Alzheimer’s disease (AD), they do not know why some people develop dementia and others do not. Amyloid plaque is not a good predictor of who will or will not develop AD.
Can People Catch Dementia?
Ask most neuroscientists about dementia and you will be told unequivocally that it is not transmissible. That is not entirely true. We have known about a neurodegenerative disease called CJD (Creutzfeldt-Jakob disease) for more than 100 years.
It is described this way (StatPearls, March 9, 2022):
“Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, rare, transmissible, universally fatal, neurodegenerative condition caused by prion proteins.”
“It belongs to a group of transmissible spongiform encephalopathies that can affect people worldwide with an incidence of one case per million per year.”
What Is a “Prion?”
The article above in StatPearls describes CJD:
“The infectious agent is ‘prion’ (a protein) that can be transmitted either by direct contact with contaminated tissue (iatrogenic) or via inheriting a mutation in the prion protein gene (familial)…The word ‘prion” derives from the words ‘proteinaceous’ and ‘infectious…”
Mad Cow Disease?
Perhaps you remember headlines about Mad Cow Disease, also known as BSE or bovine spongiform encephalopathy. Researchers believe that this progressive neurodegenerative disease is caused by prions. It can be spread from cow to cow or through contaminated meat-and-bone meal (MBM).
It can take years for cows to develop symptoms of BSE.
“Strong evidence indicates that classic BSE has been transmitted to people primarily in the United Kingdom, causing a variant form of Creutzfeldt-Jakob disease (vCJD)… Since vCJD was first reported in 1996, a total of only 231 patients with this disease, including 3 secondary, blood transfusion-related cases, have been reported worldwide. The risk to human health from BSE in the United States is extremely low.”
We interpret that as good news and bad news. The good news is that CJD is “extremely” rare. The bad news is that some forms of neurodegenerative diseases are indeed transmissible. That is why the latest research has captured headlines.
Did Some People Catch Alzheimer’s Disease? New Study Raises Critical Questions:
A study published in Nature Medicine (Jan. 29, 2024) is sending ripples through the Alzheimer’s research community. The research was kicked off because clinicians in the UK discovered a number of patients who had developed Alzheimer’s disease (AD) before they were 60.
That in itself might not have garnered attention. There are cases of early-onset AD.
But some of the cases were in their 40s and 50s:
“Symptom onset was between the ages of 38 years and 49 years in four patients (cases 3, 4, 5 and 8) and at age 55 years in the remaining patient (case 2). In three of these five patients (cases 3, 4 and 8), a diagnosis of Alzheimer’s disease had been made before referral to the NPC; two individuals presented with typical amnestic symptoms (cases 4 and 8) and met National Institute on Aging and Alzheimer’s Association (NIA-AA) diagnostic criteria for probable Alzheimer’s disease, and the other individual (case 3) presented with non-amnestic (language) symptoms.”
The researchers reviewed medical records from these patients. They did not have the known genetic mutations that are thought to cause early-onset dementia.
What they did have in common, however, was a history of childhood injections of human growth hormone (HGH) that had been extracted from the pituitary glands of cadavers.
Human Growth Hormone and Cadavers?
Growth hormone therapy was started in the 1950s for children who were deficient in this hormone. These kids experience slow growth starting early in childhood and often end up much shorter than their peers. Before scientists learned how to create biosynthetic rhGH (recombinant human GH) they extracted the growth hormone from cadavers. It was known as c-hGH (cadaveric pituitary-derived growth hormone).
“Between 1959 and 1985, at least 1,848 patients in the United Kingdom were treated with human cadaveric pituitary-derived growth hormone (c-hGH). Worldwide, over 200 cases of iatrogenic CJD have occurred as a consequence of childhood treatment with c-hGH, with 80 cases recorded in the United Kingdom.”
Did People Catch Alzheimer’s Disease?
The authors of the latest research in Nature Medicine (Jan. 29, 2024) conclude:
“We now provide evidence that Alzheimer’s disease is also transmissible in certain circumstances and, therefore, that Alzheimer’s disease (like Aβ-CAA [cerebral amyloid angiopathy]) has the full triad of etiologies (sporadic, inherited and rare acquired forms) characteristic of conventional prion diseases. This should further emphasize that the principles of prion biology have relevance for other neurodegenerative diseases involving the accumulation of diverse assemblies of misfolded host proteins, which may have propagating and neurotoxic forms.”
These cases suggest that, in rare instances, Alzheimer’s disease could be transmitted. This research raises questions about the role of amyloid beta (Aβ) as the sole cause of Alzheimer’s disease.
Could AD Be Infectious? Can People Catch Alzheimer’s Disease?
We have established that there are rare instances when a neurodegenerative disease can in fact be transmitted. Creutzfeldt-Jakob disease is one example. Now we have learned that some recipients of cadaveric pituitary-derived growth hormone also developed signs and symptoms of AD.
Could there be other infectious agents that might contribute to dementia? In other words, can some people catch Alzheimer’s disease?
We first stumbled upon the idea that Alzheimer’s disease might be infectious when we read articles by Melvyn J. Ball, MD. He was a pathologist at the Oregon Health Science University. In an article in the Canadian Journal of Neurological Sciences (Aug. 9, 1982) Dr. Ball proposed that the herpes simplex virus (HSV) that causes cold sores might also damage brain tissue.
Everyone knows that the herpes virus can travel down from the trigeminal ganglia in the brain to the lips and cause a cold sore. Dr. Ball proposed that hibernating viruses could also travel deeper into the brain and cause AD-like lesions.
“It is suggested that reactivation of the same dormant viral material travelling centripetally instead might be the cause of the ‘degenerative’ lesions typical both of Alzheimer’s Disease and of the normal aged human brain.”
Dr. Ball forged on:
Sadly, very few neurologists paid any attention to Dr. Ball’s hypothesis. But he did not give up.
In 2006 he wrote in the Journal of Alzheimer’s Disease:
“…during my elusive search, evidence has been slowly gathered that reactivation of latent Herpes simplex virus, traveling from trigeminal ganglia into neighbouring mesial temporal cortex, might best explain the limbic predilection for and earliest site of neurofibrillary tangle formation.”
Other Researchers Suggest an Infectious Cause for AD:
We have written extensively about infections and Alzheimer’s disease. Here is an article that we wrote tracing some early research back to 1974.
Many years ago we were honored to interview Dr. Robert Moir, a Harvard scientist who studied the role of infections as a causative factor in the development of Alzheimer’s disease. You can listen to this radio show at this link. You can also read about more recent research linking infection to AD at this link.
If You Could Catch Alzheimer’s Disease, Can you Prevent AD?
Here is a question that most neuroscientists and drug companies seem to shy away from. Can antiviral herpes drugs reduce the risk of Alzheimer’s Disease? You can read our answer to that question at this link. You will learn about British neuroscientist, Dr. Ruth Itzhaki. Like Dr. Ball, she has been working in the wilderness for many years. Her work is also fascinating.
Would Vaccines Work to Prevent AD?
If there is a possibility that infections could trigger the destruction that leads to Alzheimer’s disease, could vaccination prevent the process from starting? I want to reinforce the idea that most neuroscientists find such an idea preposterous. And yet there are data to support this hypothesis.
Here is a link to our article titled:
So, can you catch Alzheimer’s disease? Most neuroscientists would still say absolutely not! They would be wrong, of course. That’s because the latest research shows that prions are transmissible and can lead to neurodegenerative disease. Neurologists will quickly point out that such cases are extremely rare. They would be absolutely right! But the evidence is there that, though rare, there is the possibility to catch Alzheimer’s disease.
The much bigger question is: can viral infections like herpes also trigger a chain of events that could lead to an immunological reaction causing brain damage? Given that most funding agencies hate that idea, it is unlikely that we will get a definitive answer any time soon.
There is also the looming question: will people who caught COVID-19, especially those who developed long COVID, be more vulnerable to cognitive dysfunction down the road? Hopefully, some brave young investigators, following in the footsteps of Drs. Melvyn Ball and Ruth Itzhaki, will forge on and break new ground in the fight against dementia.
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