Question Lingers Over Relationship Between Dementia and Tooth Loss

Question Lingers Over Relationship Between Dementia and Tooth Loss

Scientists on two continents have produced conflicting reports about whether a relationship exists between tooth loss and dementia. While a study in Japan found significant associations between older adults who had lost their teeth and incidences of dementia, a study of subjects at a Minnesota geriatric dental clinic reported no association between the two conditions. While the efforts produced differing conclusions, both studies reflect the impact poor oral health can have on systemic health.

The Japanese-based study led by Dr. Nozomi Okamoto of Nara Medical University School of Medicine in Kashihara declared a “significant relationship” between tooth loss and mild memory impairment and cognitive impairment. It also offered four possible biological explanations for the relationship. The first proposed cause was connected to periodontal diseases and the systemic inflammation associated with the conditions. The researchers proposed a second cause might lie in genetic risk factors related to periodontal diseases and cognitive function. A third explanation suggests that when teeth are lost there is also a decrease in the number of sensory receptors around the teeth. The loss of these receptors may trigger a learning disorder. The final cause the researchers considered could stem from various biologic and non-biologic risk factors, such as low socioeconomic status, negative early-life events, certain head traumas and diet. Test subjects included 4,206 male and female subjects age 65 or older who live within the prefecture of Nara, Japan.

As noted, United States researchers analyzing a similar geriatric population found contrasting results. A community-based geriatric dental clinic in Minnesota was the focus of the study led by Xi Chen, DDS, PhD, assistant professor in the Department of Dental Ecology at the School of Dentistry, University of North Carolina in Chapel Hill. The study population included 491 older adults, of which 119 were classified as having dementia. Prior to enrolling in the study all subjects received treatment for their existing dental conditions, and treatment was delivered to all subjects throughout follow-up.

The US study analyzed data that included tooth loss patterns, number of tooth loss events, and number of teeth lost per patient per year. Data were compared for study subjects who had dementia and for those who did not have dementia. After 4 years the study found 31% of subjects without dementia had lost at least one tooth compared to 37% of subjects with dementia. Despite some differences, the report stated the findings between the two groups did “not significantly differ.” Chen’s investigation pointed out that poor oral health was observed from the outset of the study in both groups. The report concluded, however, “Participants with dementia maintained their dentition as well as participants without dementia when dental treatment was provided.”

Source: Behavioral and Brain Functions, December 2010; Journal of the American Geriatrics Society, December 2010