Alzheimer’s disease could be caused by a gum infection, according to a new study.

The study, published this week in the peer-reviewed journal Science Advances, suggests the bacteria Porphyromonas gingivalis that destroys gum tissue in the mouth is linked to dementia and Alzheimer's.

Researchers observed the bacteria in the brains of people with Alzheimer's disease. They also conducted tests on mice that showed the gum infection led to an increased production of amyloid beta, a part of the amyloid plaques associated with Alzheimer's disease.

"Despite significant funding and the best efforts of academic, industry, and advocacy communities, clinical progress against Alzheimer's has been frustratingly slow," Casey Lynch, author on the paper and CEO of pharmaceutical company Cortexyme, said in a statement. "The Science Advances publication sheds light on an unexpected driver of Alzheimer's pathology."

Cortexyme, which funded the research, is designing a series of therapies to treat the gum infection that plan to go to Phase 2 and 3 clinical trials.

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While there have been previous studies linking periodontal disease and Alzheimer’s, researchers who aren't affiliated with the paper say there isn't clear enough evidence linking the two.

"In research we’ve supported to uncover the key risk factors for Alzheimer’s disease, gum disease hasn’t emerged as a major cause for concern," James Pickett, the head of research at Alzheimer’s Society who was not involved in the paper, said in a statement.

No cure currently exists for Alzheimer's disease, the most common type of dementia. The disease that begins with memory loss affects as many as 5 million Americans, according to the Centers for Disease Control and Prevention.

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