Does gum disease cause Alzheimer's?
Alzheimer’s disease is a degenerative brain disease, the most common cause of dementia and includes symptoms such as difficulties with memory, language and a loss of cognitive skills. In Alzheimer’s disease, neurons involved in cognitive function have been damaged or destroyed. Neurons in other parts of the brain are eventually damaged or destroyed as well, including those that enable a person to carry out basic bodily functions. Alzheimer’s disease is eventually fatal, and is the sixth leading cause of death in the United States.
Alzheimer's has long been difficult to diagnose, and even more difficult to treat, until significant impairment is experienced by the patient. An incomplete understanding of the underlying causes has mystified both scientists and medical professionals. A recent development, however, may shed light on this devastating disease. Researchers have discovered evidence of the link between bacteria in gum disease and people with dementia, and published their findings in the journal Science Advances.
The international team confirmed that P. gingivalis can be found in the brains of deceased people with Alzheimer’s. In more than 90% of the brain samples with confirmed Alzheimer’s, they found toxic enzymes produced by the bacteria called gingipains. Brains with more gingipains had higher quantities of the proteins associated with Alzheimer’s. Tests on mice confirmed the bacteria could travel from the mouth to the brain and showed that gingipains destroyed brain neurons. The bacteria also increased production of amyloid beta, a component of the amyloid plaques commonly associated with Alzheimer's.
The researchers then gave the mice a drug that binds gingipains and it reduced the β-amyloid production and neurodegeneration. Initial tests with human volunteers demonstrated that a similar drug showed signs of improving cognition in a small group of patients with Alzheimer’s; a larger study is targeted for this year.
Not all scientists agree with the conclusions drawn in the study-some say it is still not clear whether gum disease bacteria is driving the development of Alzheimer's. The research may have uncovered a relationship between gum disease and Alzheimer's, but gum disease may not necessarily be the cause. Patients with Alzheimer's are more susceptible to infections in general, so it may be that the gum disease bacteria and the toxic proteins they secrete are a by-product of Alzheimer's rather than a cause.
Although the Cortexyme study is “the largest to date” to find P. gingivalis in Alzheimer’s brains, and it “is clearly very comprehensively approached,” says neurologist James Noble of Columbia University, who has studied the link between periodontal disease and Alzheimer’s.
Other pathogens have been found in the brains of people with Alzheimer’s, including spirochete bacteria, which can cause Lyme disease, and some herpesviruses. Previous studies have shown that β-amyloid in the brain appears to protect mice from bacterial and viral infections by a trapping mechanism. Too much of this protective response could trigger the buildup of amyloid plaques.
Since nearly 50% of the U.S. adult population has gum disease, these results are potentially significant for a large segment of the population. Although the connection between gum disease and Alzheimer’s is not conclusive, it's better to stay on the safe side and reduce risk the old fashioned way: brush and floss.