Excerpted from Chapter 5 of Beyond Alzheimer's by Scott D. Mendelson
Bad Teeth
The elderly are far more likely than the young to suffer tooth loss. It is well known that elderly individuals with dementia have poor dental hygiene habits. Many lose their teeth, and, when teeth remain, there is a greater risk of cavities, gum disease, and further tooth loss than is seen in individuals their age without dementia. In view of these facts it is not surprising that studies have shown a direct relationship between the number of teeth a person has and the likelihood of having dementia. However, while dementia can increase the risk of dental disease, the opposite might also be true. That is, there is evidence that dental disease, gum disease and tooth loss may increase the risk of developing dementia.
In a study of comparison between twins, tooth loss before the age of 35 was found to be a significant factor in determining the likelihood of later developing Alzheimer’s dementia. In a Korean study, elderly subjects who were free of dementia were evaluated for dental health and number of teeth. It was found that those with the fewer number of teeth, particularly if they did not wear dentures, were most likely to develop Alzheimer’s Dementia in the following years. A European study of elderly nuns found similar results. A perfectly reasonable explanation is that people without teeth are not able to eat properly or absorb necessary nutrients, which would put them at higher risk for dementia. Although this is true to some degree, the relationship between tooth loss and dementia appears to be more complicated than that.
For many years it has been suspected that infections of the teeth and gums can increase the risk of certain types of heart disease. It is known, for example, that the atherosclerotic plaques that build in arteries and cause heart attacks and strokes, are often populated by bacteria that live in the mouth. In a study published in the Archives of Internal Medicine in 2000, it was found that gum disease is “an important risk factor” for stroke. Any factor that increases the risk of cardiovascular disease and stroke also increases the risk of Vascular Dementia and, most likely, other forms of dementia.
A particularly disturbing finding is that a spirochete bacteria of the type called Treponema is often found in the brains of people diagnosed with Alzheimer’s Dementia. Treponema denticola and related spirochetes are bacteria that normally populate the human mouth. They particularly like plaque that forms on the teeth at the gum line. The numbers of Treponema denticola and its relatives dramatically increase in gums that are infected, which is a relatively common condition called gingivitis. It is suspected that these Treponema bacteria may find there way from the gums into the trigeminal nerve that supplies the teeth with sensation, migrate up into the brain, and set up housekeeping. Once established in the brain, chemical or immunological characteristics of these bacteria appear to trigger neurodegenerative changes that cause dementia. It would not be terribly surprising for a spirochete bacteria to act in this way. Two other even more malign spirochete bacteria, Treponema pallidum, which causes syphyllis, and Borrelia burgdorferi, which causes Lyme disease, are both known to cause similar problems when they infect the brain.
In one of the strangest studies I have ever read, it was shown that simply removing the molars of old rats causes decreases in both spatial memory and the release of the neurotransmitter acetylcholine in certain areas of their cerebral cortex. You might recall that most drugs approved by the FDA to treat dementia act by increasing the amount of acetylcholine in the brain. This puzzling study would be easy to dismiss were it not for the fact that very similar findings were reported when the molars of aged SAMP8 strain mice were removed. SAMP8 mice are rodents genetically engineered to exhibit changes in the brain and behavior quite similar to those seen in humans with Alzheimer’s Dementia. Mice that were quaintly described as being in “the molarless condition” had decreases in the amount of acetylcholine in the hippocampus of the brain, which something also found in human Alzheimer’s patients. Curiously, young SAMP8 mice subjected to “the molarless condition” did not have these reductions in acetylcholine activity. These findings lend an entirely new flavor to the old term “wisdom tooth”.
All in all, it seems clear that poor dental hygiene can contribute to dementia by making it difficult to eat and get proper nutrition, or by being a source of infection that can spread into the blood and, perhaps, directly into the nervous system from the mouth. It might further contribute through some mysterious and as of yet unexplained mechanism of lowering acetylcholine levels in the brain after teeth are lost.
Excerpted from Chapter 5 of Beyond Alzheimer's by Scott D. Mendelson
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