A new study of dementia led by USC researchers revealed that missing teeth and chronic inflammation of the mouth at an early age quadruples the risk of developing Alzheimer's disease.
The study, which was presented at the first Alzheimer's Association International Conference on Prevention of Dementia last week, examined the histories of over a hundred pairs of identical twins. Each pair consisted of one twin who had developed dementia, and one who had not. Acting on the premise that identical twins share an identical genetic blueprint, the study looked into external factors that could have led to the mental demise of the demented twin.
Along with researchers from Stockholm, Florida and UCLA, lead author Margaret Gatz, a psychology professor at USC, looked into the Swedish twin registry and hand-selected pairs of identical twins that fit a certain criteria.
"We screened everyone in the twin registry for cognitive impairment and did complete clinical evaluations with a physician and a nurse for everyone who we diagnosed with dementia," said Gatz, who has been studying twins and dementia for 20 years.
"The physician and nurse spent several hours visiting the person and determining the correct diagnosis based on the type of protocol that would be used at any leading medical center," she said, describing the data collection process.
Dementia is an umbrella term that includes Alzheimer's disease, and once properly diagnosed in the twins examined, researchers looked into several potentially modifiable risk factors that could have brought it on.
Among these were periodontal disease before age 35, the experience of a stroke before the onset of dementia, physical exercise between ages 25-50 and years of education.
The study, titled "Potentially Modifiable Risk Factors from Dementia: Evidence From Identical Twins," found that a stroke can increase the risk of dementia (but not Alzheimer's specifically) in later years six-fold, while periodontal disease in early years quadruples that risk.
But the link between periodontal disease and Alzheimer's does not mean that extra flossing will ward off dementia, said Gatz, adding that slogans like "Brush your teeth: Prevent Alzheimer's disease" are overly simplistic.
Instead, periodontal disease should be seen as a signpost for exposure to inflammation, which in turn can go on to damage brain tissue and lead to dementia, Gatz said.
"The most important preventative action supported by our findings is that it is important to maintain good cardiovascular health, and that good cardiovascular health might help to maintain the brain's health," said Gatz.
"This is not a new finding, but our results support what others have found," said Gatz, who added that it was the work of gerontologists at USC that inspired her study.
USC gerontology professors Caleb Finch and Eileen Crimmins have written about inflammatory load and lifespan.
Finch, an Alzheimer's expert, said, "I think Professor Gatz's findings have great potential significance."
"They are the first strong indication that chronic infections are a factor in Alzheimer disease. These findings further demonstrate Dr. Gatz as leading researcher in twin studies of aging," he said.
Professor Roberta Brinton, also and Alzheimer's expert and director of the USC STAR Science Education Program, said, "Dr. Gatz's findings are crucial to our understanding of the genesis of age associated Alzheimer's disease."
"The role of inflammatory processes in the progression of Alzheimer's is now fairly well accepted. Dr. Gatz's findings which builds on those of our USC colleagues Drs. Caleb Finch and Eileen Crimmins, is provocative and suggests that inflammatory events early in life predispose development of neurodegenerative disease much later in life," she said.
If the link between periodontal disease and dementia is confirmed, it would add inflammatory burden to the as-yet short list of preventable risk factors for Alzheimer's.
Gatz's study was funded by the Alzheimer's Association and the National Institute on Aging.
