Now here's another compelling reason to religiously brush one's teeth: researchers have found that periodontitis or gum disease speeds up cognitive decline in people with early-stage Alzheimer's disease by six times.

Periodontitis is common among the elderly and can become worse during old age as people struggle to maintain good oral hygiene. Bad bacteria in the gums are linked to increased levels of inflammation in the body, in turn associated with increased mental decline in Alzheimer's patients.

The joint research from King's College London and the University of Southampton followed 59 individuals with mild to moderate Alzheimer's for six months, assessing their dental health. The six-fold rise in cognitive decline, as well as an increased in inflammation levels, was detected in those with gum disease at the beginning of the study.

Since it was a small study, the authors advice conducting a bigger one to investigate the mechanisms by which gum disease may lead to decreased cognition. A growing body of research, however, supports the link between decreased cognitive states and inflammation, suggesting the benefits of gum disease treatment to Alzheimer's and dementia cases.

"These are very interesting results which build on previous work we have done that shows that chronic inflammatory conditions have a detrimental effect on disease progression in people with Alzheimer's disease," says senior author and University of Southampton professor Clive Holmes.

The findings were published in the journal PLOS ONE.

Gum disease is prevalent both in the United States and the United Kingdom, particularly among older segments. It is deemed a major cause of tooth loss — a UK study found that 40 percent of adults ages 65 to 74 — half of which reporting periodontitis beforehand — retained less than 21 of their original teeth.

Bacteria and viruses are a close target in probing Alzheimer's.

A team of 31 experts suggested the disease could be rooted in the herpes virus or chlamydia, while researchers from Oxford, Cambridge, and Imperial College London believed that bacterial and viral infections in the brain often exhibited symptoms similar to those of Alzheimer's.

Dementia, the most common form of which is Alzheimer's, covers various degenerative conditions that lead to gradual brain function loss, including memory, thinking and reasoning. Its causes remain largely unknown, although scientists point to genetic, lifestyle and environment as likely factors to consider.

Photo: Patrick Doheny | Flickr