Adding to research suggesting that vaccines for certain viral diseases may make someone less vulnerable to dementia later in life, a recent study demonstrates an association between shingles vaccinations and reduced dementia risk. MedRxiv published an observational, non-peer reviewed study that links Zostavax, a Shingles vaccine, with a 20% lower risk of dementia. While research on this relationship is still in its early stages, it is an exciting development in the study of dementia and Alzheimer’s disease.
A Natural Shingles Experiment
Shingles is a semi-common disease that affects older adults when the virus that causes chickenpox, varicella zoster virus (VZV), re-emerges in the body. VZV stays in the body after it enters as chickenpox and — if it reactivates, causes a painful blister rash and sometimes lasting pain. The researchers analyzed the health records of 300,000 people living in Wales in 2013 when the Zostavax vaccine became available. People born on or after September 2, 1933, were eligible for the vaccine. Those born earlier were not. The researchers found that those who were eligible for the vaccine and received it were about 20 percent less likely to be diagnosed with dementia over the seven-year follow-up period, compared to the ineligible group.
Zostavax is no longer widely used. After only a few years of public use, Zostavax was proven to not be as effective as promised and caused many health problems. The US began to use Shingrix as a replacement vaccine in 2019 and Wales followed suit in 2021.
A Promising Discovery
This is not the first time scientists have suspected a link between a viral infection and dementia. In 1991, biophysicist Ruth Itzhaki found herpesvirus in the brains of deceased Alzheimer’s patients during her own research. Itzhaki commented on the medRxiv’s report, saying “It’s totally consistent with what we’ve been saying since 1991 and very gratifying.” She also commented on the fact that the medRxiv study filters out confounding factors that could lead to the vaccinated groups lowered dementia risk, according to Nature.com.
Finding the True Cause
In 2018, Leslie Norins, an immunologist, funded a private research study to attempt to find a link between a microbe and Alzheimer’s disease. His team proposed that infections can cause the body to produce amyloid clumps, which accumulate in the brain and hinder function.
Amyloid in its regular production can act as a barrier for the brain and protect the brain from infection. When its natural production is disrupted, amyloid can cluster and disrupt neuronal function, leading to cell death.
While these studies point to a correlation between vaccination and reduced risk of Alzheimer’s disease, scientists cannot claim causation. Amyloid buildup has been found in many other post-mortem patients that did not have Alzheimer’s disease, and it hasn’t been proven that dissolving these clusters can treat or cure the disease.
That being said, vaccinations do improve health in general. Scientists are keen to follow developments in this area. Alberto Ascherio, an epidemiologist at Harvard University said to Nature.com that, “If it is true, it’s huge,” adding that “even a modest reduction in risk is a tremendous impact.”
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