Could Alzheimer's Be Linked to a Bacterial Infection?
What We Know About Alzheimer’s Disease
To understand the virus theory, we first need to understand how Alzheimer’s disease works. In the simplest terms, Alzheimer’s happens when the brain stops processing proteins correctly, causing a build-up of hard plaques on brain cells.
These plaques are made of proteins called amyloid and tau. Everyone has amyloid proteins in their brain, but in a brain with Alzheimer’s, the body is not able to break down and process proteins properly, which leads to build-ups of hard amyloid plaques. These plaques interfere with the cells’ ability to function.
The same goes for a protein called tau. Normally, the brain uses tau as a binding agent. In a healthy brain cell, tiny tubes help carry substances in and out of the cell — tau helps stabilize these tubes. However, in a brain with Alzheimer’s, molecules of tau detach from the tubes, and begin sticking to each other instead. These tangles of misplaced tau molecules make it harder and harder for the brain cells to communicate with one another.
Researchers know that amyloid plaques and tau tangles cause the cognitive decline, and are found in unusually high levels in the brains of those with Alzheimer’s. What they don’t know is why.
Why a Virus or Bacteria May Be the Cause
In a 2007 study, researchers noticed something strange about people with Alzheimer’s: they had fewer teeth than people with healthy brains. Now, over a decade later, scientists finally think they may know why.
In 2016, researchers discovered that amyloid proteins may actually be part of the brain’s defense mechanism. The protein can act as an anti-microbial, killing bacteria to protect the brain. The problem is that when the brain goes into overdrive to protect itself, the amyloid proteins build up over time, developing into plaques.
To be clear, it isn’t the bacteria itself that scientists believe causes Alzheimer’s — it’s the build-up of protein plaques. In other words, Alzheimer’s disease is collateral damage.
So what does this have to do with oral hygiene? New evidence suggests that the bacteria invading Alzheimer’s brains is none other than P. gingivalis — or in layman’s terms, gingivitis.
In a study of 54 brains with Alzheimer’s, evidence of P. gingivalis was found in the hippocampus region of 99 percent of subjects. The hippocampus is an important area for memory. Researchers also discovered that when researchers gave gingivitis to mice, it created tau tangles, amyloid plaques and other telltale Alzheimer’s symptoms.
And, according to some scientists, gingivitis isn’t the only suspect. Scientists believe that amyloid proteins may also be protecting against other viruses, specifically those in the herpesvirus class. They discovered that people who had previously had shingles, cold sores or genital ulcers were more likely to develop Alzheimer’s later in life.
Even more amazing, a study found that people treated with herpes medication were 10 times less likely to develop Alzheimer’s.
A Cure in Sight?
While these new findings may bring us closer to solving the mystery of Alzheimer’s and dementia, scientists have yet to determine a definitive cause for the disease. That’s because Alzheimer’s is complex and research exploring the correlation between bacteria and Alzheimer’s disease is at a very early stage. These early studies help researchers understand the disease process. However, looking at the presence of bacteria in human brain tissue doesn't tell us anything about whether this may have a role in causing the disease. There are also other factors at play, such as genetics, and these will need to be taken into consideration.
But if collateral damage from bacteria or viruses really could be the cause of Alzheimer’s, this gives us hope that we may be closer to discovering a potential cure.
Do You Know Someone with Alzheimer’s?
Are you or a loved one affected by Alzheimer’s disease or dementia? We’re here to help. Read more of our resources on Alzheimer’s and dementia here. And if you’ve got questions about senior living or memory care, feel free to give us a call.
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