In a new paper led by senior author Jan Potempa, a microbiologist from the University of Louisville, researchers report the discovery of Porphyromonas gingivalis - the pathogen behind chronic periodontitis (aka gum disease) - in the brains of deceased Alzheimer's patients.
'We've known that sleep problems and Alzheimer's are associated in part via a different Alzheimer's protein - amyloid beta - but this study shows that sleep disruption causes the damaging protein tau to increase rapidly and to spread over time.
Another study found people with mild to moderate Alzheimer's who had gum disease experienced a quicker rate of cognitive decline compared with those without.
When the team examined the brains and cerebrospinal fluid of Alzheimer's patients, they found DNA from the bacterium.
A team of scientists from the University of Louisville found P. gingivalis in the brains of deceased people who suffered from Alzheimer's.
The report quoted Sim Singhrao of the University of Central Lancashire in the United Kingdom as saying: "This is the first report showing P. gingivalis DNA in human brains, and the associated gingipains, co-localising with plaques".
A bacterial infection better known for causing gum disease may be leading to the development of Alzheimer's disease in some patients by entering the brain and releasing enzymes that attack important proteins.
Casey Lynch of Cortexyme was quoted as saying some brain samples with Alzheimer's showed the presence of the bacteria and the two proteins but at lower concentrations.More news: Renault convenes board to turn page on Carlos Ghosn era
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"Not enough people are asking what is upstream of the plaques ... and [brain] inflammation", said Lynch, who has a background in Alzheimer's research and was frustrated by the string of failed therapies for the disease.
Laboratory tests indicated that gingipain enzymes may trigger tau tangles - knots of proteins within neurons that are thought to drive the damage caused by Alzheimer's.
The researchers who carried out the study mostly worked at Cortexyme, a private biotech company, with others working at Jagiellonian University in Poland, the University of California, University of Louisville School of Dentistry and Harvard University School of Dental Medicine in the USA, the University of Melbourne in Australia, and University of Auckland in New Zealand. If the findings are shown to be correct, this could offer one reason for why 5.7 million Americans are now living with Alzheimer's disease: a figure set to rise to 14 million by 2050. What's more, when mice were treated with a drug blocking the enzymes, the neurodegeneration stopped. 'A couple of years ago it was suggested [amyloid] accumulation might actually be part of the brain's innate immune system for dealing with bacteria, ' he says. We don't know for sure that P. gingivalis causes Alzheimer's disease in humans, or that the drug will work. The study also finds that in mice, the bacteria trigger brain changes typical of the disease. "He points out that while most of the data presented in the Cortexyme study supported their hypothesis, gingipains weren't found in all of the Alzheimer's-affected brains, 'so whilst it may be a cause, the data don't exactly support it being the only cause".
Alzheimer's disease, an irreversible and progressive brain disorder that leads to memory loss and diminished thinking skills, affects at least 5 million Americans. But he stressed this won't prevent the brain from becoming infected by P. gingivalis.
BDA scientific adviser Professor Damien Walmsley said: "This study offers a welcome reminder that oral health can't remain an optional extra in our health service".
"Success of this new drug depends on whether the infection really does play an important role in Alzheimer's disease".
But, alternatively, it may be that people with Alzheimer's have poorer oral hygiene, perhaps because the condition makes them less able to look after their teeth and gums.
"Despite the involvement of a virus, the [Alzheimer's] disease is apparently not contagious", she told Newsweek. "We will have to see the outcome of this ongoing trial before we know more about its potential as a treatment for Alzheimer's", he said.