New Link Found between Alzheimer's & Gum Disease Bacteria

The researchers looked at brains of deceased people with Alzheimer's disease and found evidence of Porphyromonas gingivalis (Pg), a type of bacteria that's associated with gum disease. They also found evidence of gingipains, toxic enzymes produced by the bacteria, in brain samples of people with Alzheimer's, Science Magazine reported.

They also conducted an experiment on mice, infecting their gums with Pg. Later, they detected the bacteria and higher than normal levels of amyloid beta (a protein associated with Alzheimer's) in the mouse brains. In further mouse experiments, the researchers tested a drug designed to bind to gingipains. The drug helped reduce the amount of Pg bacteria and block the production of amyloid beta in the animals' brains.

"The findings of this study offer evidence that Porphyromonas gingivalisand gingipains in the brain play a central role in the pathogenesis [Alzheimer's disease], providing a new conceptual framework for disease treatment," the authors wrote.

Experts who weren't involved with the new study have interpreted the findings with caution, calling for more research. Still, two dentists told INSIDER that there are plenty of other ways that gum disease can negatively affect health.

Some earlier studies do support the idea of a link between oral health and Alzheimer's. CBS News cited two specific studies in its report. One from 2017 found that people who had gum disease for 10 years had a higher risk of developing Alzheimer's. A small study from 2016 in people with mild to moderate dementia found an association between gum disease and higher rates of cognitive decline.

But, in response to the new study, some scientists have said there's still not enough evidence to say that microbes like Pg definitively cause Alzheimer's.

"The idea that bacteria and viruses may play a part in brain disease like Alzheimer's is not necessarily new," Dr. Rebecca Edelmayer, director of scientific engagement for the Alzheimer's Association, told CBS News. "But what this paper suggests is really an association and not causation ... More research is needed to really identify a causative role for microbes."

"I'm fully on board with the idea that this microbe could be a contributing factor. I'm much less convinced that [it] causes Alzheimer's disease," neurobiologist Dr. Robert Moir, or Massachusetts General Hospital, told Science Magazine.

And Dr. James Pickett, head of research at the UK Alzheimer's Society, told CNN that, even though the new study suggests Pg infection could damage brain cells, "there isn't yet clear evidence that it can cause this damage in people or result in Alzheimer's."

Edelmayer also told CBS News that it's too early to say whether good oral care could help prevent Alzheimer's disease.

According to the Centers for Disease Control and Prevention (CDC), scientists still don't fully understand what causes Alzheimer's disease. Right now, the best-known risk factor for the illness is age.

New research aside, dentists have long known that gum disease can wreak havoc on the mouth. It's also very common: Almost half of all US adults over age 30 have some type of gum disease, according to the CDC.

"Honestly, with teeth, everyone thinks the number one problem is cavities, but it's actually gum disease," dentist Dr. Nammy Patel, owner of Green Dentistry in San Francisco, told INSIDER.

Gum disease is an infection affecting the tissue that holds your teeth in the right place. Typically, it's caused by poor oral hygiene, which allows plaque, a sticky film of bacteria, to build up on the teeth. In advanced stages of gum disease, plaque spreads below the gum line, prompting an inflammatory response in which the tissues and bone that support teeth are broken down, according to the American Academy of Periodontology (AAP). The gums can start to pull away from the teeth, creating open pockets that then become infected. Eventually, it can lead to tooth loss.

Though early gum disease often has no symptoms, the AAP notes that signs can include red, swollen, tender, or bleeding gums; gums receding or pulling away from the teeth; persistent bad breath; pus between gums and teeth, and mouth sores.

In some research, gum disease has even been associated with systemic health issues.

"There have been studies going back years and years linking gum disease to a wide variety of problems, like heart disease, premature low birth weight babies, and rheumatoid arthritis," dentist Dr. Harold Katz, founder of the California Breath Clinics, told INSIDER.

There are other potentially concerning links, too. A study published last October found an association between gum disease and higher blood pressure; another from last January reported a link between gum disease and elevated cancer risk.

To prevent gum disease, you should make sure you're brushing your teeth a minimum of twice per day, Patel said.

Flossing once a day is also part of the "regular homework" for keeping gums healthy, Katz said, but if you don't like flossing and struggle to do it regularly, Patel suggested trying a water flosser instead.

"It squirts water in between the teeth," she said. "That's pretty fantastic to use as well."

The CDC also recommends getting a dental checkup at least once yearly, or more often if you have certain gum disease risk factors (like smoking, a family history, diabetes, taking medications that cause dry mouth, pregnancy, and more).

At a checkup, dentists can use a combination of visual examination, x-rays, and an instrument called a probe to check for signs of gum disease, Patel explained.

Above all, both dentists stressed the importance of paying attention to oral health.

"The biggest thing I can say is, make sure to take care of your mouth," Patel said. "The new trend really needs to be how important mouth health is for the entire body."