This discovery might help experts understand the disease a bit more.

A paper submitted by University of Louisville microbiologist Jan Potempa, found that there is a link between gum disease and Alzheimer's.

The pathogen behind chronic gum disease (a condition known officially as periodontitis) was also found in the brains of deceased Alzheimer's patients.

According to Sciencealert, it is not the first time that a link has been made between gum disease and the shrinking of the brain.

In experiments conducted with mice, oral infection with the pathogen led to brain colonization by the bacteria, together with increased production of amyloid beta (Aβ), the sticky proteins commonly associated with Alzheimer's.

Stephen Dominy, co-founder of Cortexyme, which led the research said: "Infectious agents have been implicated in the development and progression of Alzheimer's disease before, but the evidence of causation hasn't been convincing.

"Now, for the first time, we have solid evidence connecting the intracellular, Gram-negative pathogen, P. gingivalis, and Alzheimer's pathogenesis."

Toxic enzymes called gingipains, which had been produced by the gum disease bacteria had been found in the brains of people that had Alzheimer's.

They were also found in the brains of several deceased individuals who had not received an Alzheimer's diagnosis.

So it isn't 100% concrete as to whether or not gum disease causes Alzheimer's.