MINNEAPOLIS - Periodontal disease — especially the irreversible kind that causes tooth loss — could be associated with mild cognitive impairment and dementia 20 years later, according to a study published in today’s online issue of Neurology, the medical journal of the American Academy of Neurology.
“We looked at people’s dental health over a 20-year period and found that people with the most severe gum disease at the start of our study had about twice the risk for mild cognitive impairment or dementia by the end,” said study author Ryan T. Demmer, Ph.D., M.P.H., of the University of Minnesota School of Public Health. “However, the good news was that people with minimal tooth loss and mild gum disease were no more likely to develop thinking problems or dementia than people with no dental problems.”
The study involved 8,275 people with an average age of 63, who did not have dementia at the start of the study. The participants were assessed for mild cognitive impairment and dementia. They also received a full periodontal exam that included measuring gum probing depth, amount of bleeding and recession.
Participants were put into groups based on the severity and extent of their periodontal disease and number of lost teeth, with implants counting as lost teeth. At the start of the study, 22 percent of people had no gum disease, and 12 percent had mild gum disease. 12 percent of participants had severe gum inflammation, 8 percent had some tooth loss, 12 percent had disease in their molars, 11 percent had severe tooth loss, 6 percent had severe gum disease and 20 percent had no teeth at all.
The study assessed 4,559 people at the end of the study, when they had been followed for an average of 18 years. 1,569 people developed dementia during the study (19 percent). This was the equivalent of 11.8 cases per every 1,000 person-years. The study also found that of the people who had healthy gums and all their teeth at the start of the study, 264 out of 1,826 (14 percent) developed dementia by the end of the study.
For those with mild periodontal disease, 623 out of 3,470 (18 percent) developed dementia. For participants with severe gum disease, 306 out of 1,368 (22 percent) developed dementia. And 376 out of 1,611 (23 percent) developed dementia in the group with no teeth. This was equal to a rate of 16.9 cases per 1,000 person-years.
When looking at both mild cognitive impairment and dementia, the group with no teeth had about twice the risk, compared to participants who had healthy gums and all their teeth. People with intermediate or severe periodontal disease — but who still had some teeth — had a 20 percent greater risk of developing mild cognitive impairment or dementia, compared to the healthy gums group. These risk percentages were developed after researchers accounted for other factors that could affect dementia risk like diabetes, high cholesterol and smoking.
But researchers are quick to note that there is no data that proves that periodontal disease causes dementia. They also point out a limitation of the study — since initial gum examinations were made when the participants were at an average age of 63, it is possible that cognitive decline might have begun before the start of gum disease and tooth loss.
“Good dental hygiene is a proven way to keep healthy teeth and gums throughout your lifetime. Our study does not prove that an unhealthy mouth causes dementia and only shows an association. Further study is needed to demonstrate the link between microbes in your mouth and dementia, and to understand if treatment for gum disease can prevent dementia,” Demmer noted.