Relationship between chewing ability and cognitive impairment in the rural elderly
Introduction
Cognitive impairment or dementia is a common cause of disability and decreased quality of life in the elderly (Ferri et al., 2006). Therefore, prevention and treatment of cognitive impairment are becoming increasingly important given the aging population.
Age, sex, genetic and vascular factors have been reported to be associated with cognitive impairment (Beck, Benson, Scheibel, Spar, & Rubenstein, 1982; Carlo et al., 2000). Moreover, some studies have reported a relationship between oral health and cognitive impairment (Ghezzi & Ship, 2000).
In 1997, Kato et al. were the first to describe a relationship between tooth loss and spatial memory deficits in senile rats; rats without molar teeth consuming a soft diet showed worse behavioral performance than rats with molar teeth consuming a solid diet. In an epidemiological study, Stein, Desrosiers, Donegan, Yepes, and Kryscio (2007) suggested that having no or very few teeth might be a risk factor for dementia in later life. In addition, Kimura et al. (2013) reported that low chewing ability was associated with lower cognitive functioning.
In contrast, some studies have reported that loss of teeth or chewing ability was not associated with cognitive impairment (Chen, Shuman, Hodges, Gatewood, & Xu, 2010; Onyper, Carr, Farrar, & Floyd, 2011). In 2014, Teixeira et al. indicated that studies regarding a relationship between loss of teeth or masticatory deficiency and cognitive impairment are necessary, because loss of teeth and masticatory deficiency are very closely related. Because the objective assessment of chewing ability is relatively more difficult than counting the number of lost teeth, we are aware of only a few studies regarding the relationship between chewing ability and cognitive impairment. Therefore, we aimed to assess the relationship between chewing ability and cognitive impairment by objectively assessing chewing ability using color-changing gum.
Section snippets
Study participants
A total of 295 participants were recruited from elderly registered at the public health center of a rural city of Korea. Trained nurses performed oral examinations and interviewed participants and caregivers at the participants’ homes. Participants were included based on the following criteria: (1) agreed to enroll in this study by themselves or caregivers, (2) complied with the questionnaires, and (3) whose caregivers could help the examiner if necessary. Those who were not able to communicate
Results
Socio-demographic characteristics, geriatric, and cognitive function, as measured using IADL, PADL, MNA, and MMSE-DS, are shown in Table 1 in addition to the comparison of chewing ability. The mean age of all of the participants was 81.4 (70–102) years, and most of the participants were women (67.8%), lived alone (62.0%), and were being treated for a disease (83.4%). Most participants had independent PADL (79.0%), and approximately half of the participants had independent IADL (58.6%).
Discussion
In this study, we analyzed the relationship between chewing ability and cognitive impairment among rural Korean elderly. The level of chewing ability was significantly associated with cognitive function. Participants who had lower chewing ability were more likely to have lower cognitive function. To our knowledge, this is the first study showing an association between chewing ability only measured by color-changing gum that is even simple approach as an objective proxy measure for mastication
Conclusions
This study demonstrated that there was a possibility that the risk of having cognitive impairment increased among the elderly living in a rural region with lower chewing ability. Therefore it was worth more researching on the association between oral health and cognitive impairment.
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Author contributions
I and E-K Kim designed this study and drafted and wrote the original manuscript, SK Lee and Y-S Jung collected data, HC Kim and H-K Lee performed data analyses and interpreted data, M Tanaka, K Hirotsu, and A Amano provided critical comments on the original manuscript and contributed to development of the final draft.
Acknowledgments
This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2014S1A3A2044496). This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1D1A3B03934825).
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