Dental health and dementia risk

Periodontal disease is associated with later development of mild cognitive impairment (MCI) or dementia, especially in those with severe gum inflammation and edentulism (tooth loss), new research suggests (published online July 29 in Neurology)

Over a 20-year period, investigators prospectively followed more than 8000 individuals around the age of 63 years who did not have cognitive impairment or dementia at baseline, grouping them based on the extent and severity of their periodontal disease and number of lost teeth.

Results showed that 14% of participants with healthy gums and all their teeth at baseline developed dementia, compared with 18% of those with mild periodontal disease and 22% who had severe periodontal disease. The highest percentage (23%) of participants who developed dementia was found in those who were edentulous (toothless).

After accounting for comorbidities that might affect dementia risk, edentulous participants had a 20% higher risk for developing MCI or dementia compared with the healthy group.

The take-home message from this paper is that it further supports the possibility that oral infections could be a risk factor for dementia,

Prior studies have described the interrelation of tooth loss or periodontal disease and cognitive outcomes, although many reports were cross-sectional or case-control and often lacked robust confounder adjustment.

To explore the associations between periodontal status and incident MCI and dementia, the researchers studied participants in the ARIC study, a community-based longitudinal cohort consisting of 15,792 predominantly Black and White participants 45 to 64 years of age.

The current analysis included 8275 individuals (55% women; 21% black; mean age, 63 years) who at baseline did not meet criteria for dementia or MCI.

A full-mouth periodontal examination was conducted at baseline and participants were categorized according to the severity and extent of gingival inflammation and tooth attachment loss based on the Periodontal Profile Class (PPC) 7-category model.

Based on PPC categorization, 22% of the patients had healthy gums, 12% had mild periodontal disease, 8% had a high gingival inflammation index, and 12% had posterior disease (with 6% having severe disease). In addition, 9% had tooth loss, 11% had severe tooth loss, and 20% were edentulous.

Results showed that participants with worse periodontal status were more likely to have risk factors for vascular disease and dementia, such as smoking, hypertension, diabetes, and coronary heart disease.

During median follow-up of 18.4 years, 19% of participants overall (n = 1569) developed dementia, translating into 11.8 cases per 1000 person-years.

There were notable differences between the PPC categories in rates of incident dementia, with edentulous participants at twice the risk for developing dementia, compared with those who had healthy gums.

The association between periodontal disease and MCI or dementia is rooted in the infection hypothesis, meaning adverse microbial exposures in the mucosal surfaces of the mouth, especially the subgingival space.

One notion is that there could somehow be a direct infection of the brain with oral organisms, which posits that the oral organism could travel to the brain, colonize there, and cause damage that impairs cognition.

Another possible mechanism is that chronic systemic inflammation in response to oral infections can eventually lead to vascular disease which, in turn, is a known risk factor for future dementia.