Scientists have been obsessed with finding the origin of Alzheimer’s disease for decades. We know that it occurs because neurons are suffocated by amyloid plaques. Until now, science has been unable to explain how these plaques are produced, as we have not been able to decipher what happens in brain chemistry to cause them to appear. This has led many experts to investigate alternative avenues. And that is when they discovered that the origin of Alzheimer’s could lie in our mouths.
This line of research suggests that, at least in some cases, Alzheimer’s could be related to a chronic infection. And here we find a “suspect” that is well known in dentistry: Porphyromonas gingivalis, a bacterium associated with periodontitis (gum disease).
The discovery that set off alarm bells
The issue began to gain traction following a study published in Science Advances by a team led by microbiologist Jan Potempa and researcher Stephen Dominy. When analyzing the brains of people who had died with Alzheimer’s, they detected not only the presence of P. gingivalis, but also something even more significant: gingipains, enzymes that the bacteria use to “work” on body tissues.
These gingipains (to put it simply) are like tools that the bacteria use to survive and feed. According to the study, they appeared in the vast majority of the samples analyzed. And what most disturbed many researchers was that signs of these toxins were also found in the brains of middle-aged people who had not yet developed dementia.
The worst part of all this is that these hypotheses already existed years ago. That is, for years, it had been observed that Alzheimer’s patients had poor dental hygiene. However, Ockham’s razor was applied incorrectly. It was simply believed that they had poor oral hygiene because they forgot to brush their teeth due to dementia. Now, everything points to the opposite being true. The findings of these scientists show that bacterial infection is the first step. And dementia would be nothing more than the end result, after decades of cumulative damage.
Can a simple bacterium destroy your entire identity?
The mechanism of action that experts believe they have identified is both fascinating and terrifying. The bacterium P. gingivalis would take advantage of bleeding gums to enter the bloodstream. Once in the blood, it could cross the blood-brain barrier, the wall that protects our brain. From there, it would have free rein, following this process:
First, gingipains would be able to cut the Tau proteins in neurons. These would cause neurofibrillary “tangles” to form in the brain. On the other hand, we have the beta-amyloid plaques that we mentioned at the beginning of the article. Paradoxically, these new studies consider that they are not really the cause of Alzheimer’s, but rather an immune response by the brain to trap the bacteria. The problem is that, as the bacterial infection is chronic, the brain would end up destroying itself with an uncontrolled defense. In order to stop the infection, our brain ends up destroying healthy cells.
A cure for Alzheimer’s could be closer than ever
Here come the good news. Until now, science didn’t know what to do about amyloid plaques. But now that we know the origin could be a disease as simple as gingivitis, things have changed completely.
Biotech company Cortexyme developed a molecule called COR388 (atuzaginstat) capable of blocking gingipains. The 2021 clinical trial was considered a statistical failure overall, but the data hid a revealing truth: in patients who actually had a high bacterial load, the drug slowed cognitive decline by up to 57%.
That finding has revived research. In 2025, under the name Lighthouse Pharma and with a $49 million grant from the U.S. government, the SPRING trial began. Now a safer second-generation drug (LHP588) is being used and precision medicine is being applied: only patients who test positive for the bacteria in a saliva test are treated. If the results are confirmed, we would be facing a historic change: no longer seeing Alzheimer’s as an incurable mystery, but fighting it as a treatable infection.