As the population has aged, dementia has skyrocketed to become the fifth biggest cause of death worldwide, with Alzheimer’s claiming 70% of those deaths. Yet we don’t know what causes Alzheimer’s.1 Alzheimer’s, which results in progressive loss of memory and cognitive function, usually over a decade or so, is devastating both to those who have it and to those they slowly leave behind.

The condition often involves two types of proteins—called amyloid and tau—in the brain, which are among the earliest physical signs of the disease. The leading hypothesis since 1984 has been that Alzheimer’s disease is caused by the defective control of these proteins, especially amyloid, which accumulates to form large, sticky plaques in the brain.

Yet, over the past 35 years, it has become clear that this approach isn’t working. In 2018 alone, the US National Institutes of Health spent $1.9 billion on Alzheimer’s research. But according to a recent study, the failure rate of drug development for Alzheimer’s has been 99 percent.

In 2016, researchers discovered that amyloid seems to function as a sticky defense against bacteria. They found that the protein can act as an anti-microbial compound that kills bacteria. When they injected bacteria into the brains of mice engineered to make Alzheimer’s proteins, plaques developed around bacterial cells overnight.

But in the past few years, several studies have looked not at the amyloid, but at the bacteria found in the brains of people who had Alzheimer’s when they were alive. The bacteria on which researchers have mainly been focused is Porphyromonas gingivalis, the main bacterium involved in gum disease, which is a known risk factor for Alzheimer’s.

So far, teams have found that P. gingivalis invades and inflames brain regions affected by Alzheimer’s, that gum infections can worsen symptoms in mice genetically engineered to have Alzheimer’s and that it can cause Alzheimer’s-like brain inflammation, neural damage and amyloid plaques in healthy mice. A separate team found that P. gingivalis actively invades the brains of mice with gum infections. This led researchers to believe that P. gingivalis doesn’t get into the brain as a result of Alzheimer’s—but could be the cause.

It’s uncertain how P. gingivalis gets into the brain, but there are plausible routes it could take. Your mouth normally hosts a diverse and relatively stable community of bacteria, but when dental plaque builds under the edge of your gums, it can form inflamed pockets in which P. gingivalis can thrive and release toxins.

All of this is promising for the future prevention of Alzheimer’s disease. Unfortunately, it is another case of seemingly unrelated health issues caused by poor oral health. (See our blog on chronic gum conditions and heart disease.)

Until science is certain how to prevent Alzheimer’s, perhaps the best way to ensure future brain health is to take care of your teeth and gums, and the best way to take care of your teeth and gums is to schedule a visit to the office of Dr. Brei every six months.

There are many ways to contact the office of Dr. Brei. You can email us at, call us at 520-325-9000, or click here to book an appointment directly. Make an appointment today. Your brain—and your loved ones—will thank you!

1 “We May Finally Know What Causes Alzheimer’s—And How to Stop It,” New Scientist, January 2019,