One theory promoted by the new research is that cognitive impairment is causing adverse oral health.
What did the research find?
In addition, the researchers found that Hispanics with AD showed greater small blood vessel disease in the brain than non-Hispanics with AD, as well as increased amyloid angiopathy, the accumulation of protein fragments in blood vessels associated with AD. Tau, a protein in neurons, is released into brain interstitial fluid (ISF), where it can aggregate problematically in diseases like AD. "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". The scientists then tested the brains of 53 people with Alzheimer's disease, finding the toxic enzymes from P.?gingivalis in 51 of them.
Sarah Marzi, a postdoctoral researcher at Queen Mary University of London, said that the researchers "most promisingly" show changes of NfL predicting cognitive test results and thinning of the cortex, "two main symptoms of Alzheimer's Disease".
"The idea that bacteria and viruses may play a part in brain disease like Alzheimer's is not necessarily new", Rebecca Edelmayer, Ph.D., director of scientific engagement for the Alzheimer's Association, told CBS News.
Bacteria involved in gum disease and other illnesses have been found after death in the brains of people who had Alzheimer's, but until now, it hasn't been clear whether these bacteria caused the disease or simply got in via brain damage caused by the condition.
There was also caution about the fact the drug tests had been in mice.
'The upcoming clinical trial will be a crucial test to see if this can be a potential treatment for Alzheimer's'.
Researchers first compared the brain tissue of patients with and without Alzheimer's disease.
What was the previous evidence?
This funding acknowledges the decades of failure in Alzheimer's and dementia research, which has been largely based on targeting beta amyloid and tau - approaches which have so far not yielded any compelling evidence of efficacy.
Alluding to there being help for the disease, there are a several different FDA approved treatments for symptoms that come with Alzheimer's and Dementia.
The new study in humans and mice found that sleep deprivation increases levels of the key Alzheimer's protein tau.
In 2014, using a blood test that looked at 10 specific lipids in people's blood, researchers were also able to predict Alzheimer's before symptoms appeared.
So where does this leave us?
However evidence has been growing that the function of amyloid proteins may be as a defence against bacteria, leading to a spate of recent studies looking at bacteria in Alzheimer's, particularly those that cause gum disease, which is known to be a major risk factor for the condition.