Drug companies, the Alzheimer’s Association and the FDA have placed almost all their chips on the beta-amyloid theory of Alzheimer’s disease. Billions have been spent on anti-amyloid drugs such as aducanumab (Aduhelm) and lecanemab (Leqembi). Read more about this potentially misguided approach at this link. While beta-amyloid may indeed be part of the story, we have long wanted to know what amyloid is actually doing in the brain. What triggers the formation of this sticky protein in the first place? Some researchers suggest that there is a connection between viral infections and dementia and that beta-amyloid formation is the body’s reaction to invasion. They postulate that it may be part of an immune reaction that runs amok.
Viral Infections and Dementia!
Evidence has been increasing that infections may play an important role in the development of dementia. The latest study includes data from nearly 150,000 people over many decades. Researchers followed participants in the Nurses’ Health Study, the Nurses’ Health Study II and the Health Professionals Follow-up Study (Alzheimer’s Research & Therapy, Aug. 14, 2024).
People who had a bout of shingles were 20% more likely to report subjective cognitive decline subsequently than people who did not have shingles. Men with an APOE4 gene had a greater risk. For some reason, that did not show up in women.
The investigators note that the data on these healthcare cohorts show that shingles is associated with an almost 40% higher chance of stroke, with the risk lasting more than a decade. They suggest that shingles vaccination might prove protective for both stroke and dementia, but they call for further studies to confirm that link.
By the way, one of the people involved in this study was Walter Willett, MD, Dr. P.H. He is one of the most well regarded epidemiologists and nutrition scientists in the world. He is a frequent guest on The People’s Pharmacy syndicated radio show and is also the recipient of The People’s Pharmacy Award for Excellence in Research and Communication for the Public Health.
Here is how the authors of the study, including Dr. Willett, introduce their research.
“There is growing evidence that herpesviruses may influence the risk of cognitive decline and dementia. Herpes zoster (HZ), commonly known as “shingles,” is caused by reactivation of the neurotrophic varicella-zoster virus (VZV)…HZ may potentially contribute to dementia risk through neuroinflammation, cerebral vasculopathy, or direct neuronal damage, but current evidence regarding the relationship between HZ and subsequent risk of cognitive decline is conflicting.
“In three large independent cohorts, HZ was associated with an approximately 20% higher long-term risk of SCD [subjective cognitive decline].
The Take Home Message About Viral Infections and Dementia in Alzheimer’s Research & Therapy, Aug. 14, 2024:
“To our knowledge, this is the first large study to examine HZ and the risk of early subjective cognitive decline, which may be the earliest manifestation of age-related cognitive decline and may be especially sensitive among individuals who received higher education. Given the long preclinical phase of dementia, identifying a potential association between HZ and early cognitive decline is important as it may provide insight into the complex and possible causal relationship between viral infections and cognitive health, as well as offer opportunities for early risk reduction and improved public health strategies.”
More Evidence Linking Viral Infections and Dementia:
NIH researchers have reported on a relationship between viral infections and neurodegenerative diseases (Neuron, Jan. 11, 2023). They analyzed data from over 300,000 people in a Finnish biobank (FinnGen) and almost 500,000 people in the UK biobank.
These were individuals who had been diagnosed with a variety of neurodegenerative diseases such as Alzheimer’s disease, generalized dementia, vascular dementia, ALS, Parkinson’s disease and multiple sclerosis. Investigators compared these people to individuals who did not have any such neurological diseases.
The Associations Between Viral Infections and Dementia:
The authors introduce their research this way:
“Recent research has shown a definitive association between an increased risk of multiple sclerosis and prior infection with the Epstein-Barr virus (EBV). Additional concerns regarding the potential short and long-term cognitive impact of the current coronavirus pandemic have raised the priority of investigating the potential connection between viral exposures and neuroinflammation and/or neurodegeneration.”
They found that exposure to viral diseases was associated with an increased risk of neurodegeneration. Viral encephalitis was closely linked to Alzheimer’s disease. When patients had influenza with pneumonia, they were more likely to develop 5 of the 6 neurodegenerative diseases studied.
Shingles, caused by the varicella-zoster herpes virus, and intestinal viral infections were also associated with brain disorders.
The authors point out that this can be a delayed process:
“Some of these exposures were associated with an increased risk of neurodegeneration up to 15 years after infection.”
What About Herpes Viral Infections and Dementia?
The authors of this research linking viral infections and dementia point out that:
“The results described above are supported by recent findings in the literature, which suggest an association between herpes simplex virus (HSV) encephalitis and AD [Alzheimer’s disease], AD and hepatitis, genital warts and dementia, EBV and dementia, and MS and HSV. Since the discovery of an association of the 1918 flu pandemic, caused by H1N1 influenza A, with postencephalitic parkinsonism, a link between influenza and PD has been debated. A recent study using Danish data found an association between influenza and PD with an odds ratio of 1.73 up to 10 years after virus exposure. This is very similar to the hazard ratio for influenza and pneumonia in FinnGen which was 1.72.”
Preventing Viral Infections and Dementia:
The NIH investigators go on to note that “vaccines are currently available for some of these viruses, including influenza, shingles (varicella-zoster), and pneumonia.”
They suggest that vaccination might partially reduce the risk of developing neurodegenerative diseases:
“Influenza and pneumonia vaccination has been found to reduce risk for AD and PD. Shingles (varicella-zoster) vaccination is associated with a reduced risk of dementia, AD, and PD in both the United States and Wales.”
They also suggest that antiviral drugs might be beneficial:
“These findings also suggest additional avenues to explore for both the treatment and prevention of NDDs. In addition to vaccination, some studies suggest that using antivirals may reduce the risk of dementia in HSV positive patients25 or in patients with varicella-zoster virus.”
This Is NOT New!
We have written a lot about the possible connection between viral infections and dementia. Several years ago we interviewed a Harvard researcher who believed that beta-amyloid has both antiviral and antimicrobial properties. He suggested that the formation of amyloid plaque was the body’s way of fighting off infection. You can listen to this intriguing interview at this link.
More recently, we interviewed Donald Weaver, MD, PhD. He is a senior scientist at the Krembil Brain Institute at the University Health Network, Toronto, Ontario, Canada. He is a professor of Medicine (Neurology), Chemistry, and Pharmaceutical Sciences at the University of Toronto and a neurologist at the Toronto Western Hospital. His research suggests that Alzheimer’s disease might be an autoimmune disease and that many things could trigger this reaction, including viral infections. You can listen to this recent podcast at this link.
Final Words:
We think it is time to think differently about Alzheimer’s disease and dementia. Most of the drugs that have been developed to rid the brain of amyloid plaque have fizzled. Even the new ones that have been approved by the FDA, Aduhem and Leqembi, have not restored memory or been proven to reverse dementia.
Perhaps it is time to explore the connection between viral infections and dementia. Why does the body form amyloid plaque? Could vaccination help prevent some cases of Alzheimer’s disease? What about antiviral medications? If the NIH and the Alzheimer’s Association begin funding novel approaches to preventing or treating dementia, perhaps we might make more progress against this devastating disease!
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