Relationship between chewing ability and cognitive impairment in the rural elderly

Masticatory Function, Sex, and Risk of Dementia Among Older Adults: A Population-Based Cohort Study

BACKGROUND

A decline in masticatory function may indicate brain dysfunction related to dementia, but the relationship between masticatory function and dementia risk remains unclear. This study aimed to investigate whether masticatory function is associated with the risk of cognitive decline and dementia.

METHODS

Data were obtained from the nationwide prospective cohort study of randomly sampled community-dwelling Koreans aged ≥ 60 years. The 5,064 non-demented participants, whose number of chewing cycles per bite was assessed by clinical interview, were followed for 8 years with biennial assessments of cognitive performance and clinical diagnoses of all-cause dementia and Alzheimer's disease (AD). Structural brain magnetic resonance imaging was collected from a subset of cohort participants and their spouses for imaging analyses.

RESULTS

Males who chewed ≥ 30 cycles/bite had faster decline in global cognition and memory function and were at higher risk for incident all-cause dementia (hazard ratio [HR], 2.91; 95% confidence interval [CI], 1.18-7.18) and AD (HR, 3.22; 95% CI, 1.14-9.11) compared to males with less than 10 cycles/bite. Additionally, increased chewing cycles in males were associated with reduced brain volume, particularly in regions involved in compensatory cognitive control of mastication. There was no significant association between chewing cycles and the risk of dementia or brain volume in females.

CONCLUSION

Older men who frequently chew their meals could be considered a notable population at risk for dementia who should be carefully assessed for their cognitive trajectories.

Correlation between GLCM-based texture features of the lateral pterygoid muscle and cognitive function in patients with idiopathic normal pressure hydrocephalus: a preliminary report

PURPOSE

The potential relationship between mastication ability and cognitive function in idiopathic normal pressure hydrocephalus (iNPH) patients is unclear. This report investigated the association between mastication and cognitive function in iNPH patients using the gray level of the co-occurrence matrix on the lateral pterygoid muscle.

METHODS

We analyzed data from 96 unoperated iNPH patients who underwent magnetic resonance imaging (MRI) between December 2016 and February 2023. Radiomic features were extracted from T2 MRI scans of the lateral pterygoid muscle, and muscle texture parameters were correlated with the iNPH grading scale. Subgroup analysis compared the texture parameters of patients with normal cognitive function with those of patients with cognitive impairment.

RESULTS

The mini-mental state examination score correlated positively with the angular second moment (P < 0.05) and negatively with entropy (P < 0.05). The dementia scale (Eide's classification) correlated negatively with gray values (P < 0.05). Gray values were higher in the cognitive impairment group (64.7 ± 16.6) when compared with the non-cognitive impairment group (57.4 ± 13.3) (P = 0.005). Entropy was higher in the cognitive impairment group (8.2 ± 0.3) than in the non-cognitive impairment group (8.0 ± 0.3) (P < 0.001). The area under the receiver operating characteristic curve was 0.681 (P = 0.003) and 0.701 (P < 0.001) for gray value and entropy, respectively.

CONCLUSION

Our findings suggest an association between heterogeneity of mastication and impaired cognitive function in iNPH patients and highlight muscle texture analysis as a potential tool for predicting cognitive impairment in these patients.

A Cluster Analysis of Oral and Cognitive Health Indicators in the CLSA: An Exploratory Study on Cholinergic Activity as the Link

INTRODUCTION

Poor oral health has been suggested as a risk factor for cognitive decline. Yet, biologically plausible mechanisms explaining this relationship remain unknown.

OBJECTIVES

We aimed (1) to identify oral and cognitive health clustering patterns among middle-aged to elderly Canadians and (2) to investigate the extent to which these patterns could be explained by bone mineral density (BMD), a proxy measure of the cholinergic neurons' activity.

METHODS

This cross-sectional study used baseline data from the Comprehensive cohort of the Canadian Longitudinal Study of Aging (CLSA). Oral health was assessed by a self-report questionnaire, and 7 task-based instruments measured cognitive health. We identified oral and cognitive health clusters, our outcome variables, using latent class analysis. Two sets of multivariate logistic regression and 95% confidence intervals were used to investigate whether BMD explains the odds of membership in a certain oral and cognitive health group. The final models were adjusted for socioeconomic, health, and lifestyle factors.

RESULTS

Our study sample (N = 25,444: 13,035 males, 12,409 females) was grouped into 5 and 4 clusters based on the oral health status and performance on the cognitive tasks, respectively. After adjusting for all potential covariates, increase in BMD was not associated with higher odds of membership in classes with better oral health (odds ratio [OR] = 1.58 [95% confidence interval {CI}: 0.85-2.92]) and cognitive health (OR = 1.61 [95% CI: 1-2.6]) compared with the groups with the least favorable oral and cognitive health status, respectively.

CONCLUSION

Middle-aged and elderly Canadians show different oral and cognitive health profiles, based on their denture-wearing status and performance on cognitive tests. No evidence could be found to support BMD in place of cholinergic neurons' activity as the common explanatory factor behind the association between oral health and cognitive health.

KNOWLEDGE TRANSFER STATEMENT

This study is probably the first of its kind to shed light on the cholinergic system as a potential pathway influencing oral and cognitive health. Our findings may support the notion that any potential association between poor oral health and cognitive health might be explained by common contributors, helping clinicians to find the common risk factors for both conditions.

Accuracy of newly developed color determination application for masticatory performance: Evaluating color-changeable chewing gum

PURPOSE

Color-changeable chewing gums are used to evaluate masticatory performance, as measured by a colorimeter or visually based on a color scale. Although anyone can use a color scale, the evaluation accuracy depends on the evaluator. We develop an application that can determine the degree of color change in chewing gum using smartphone images, making color evaluation accurate and easy to measure.

METHODS

For the application, 60 chewed gum samples were prepared. Two shots were captured using two smartphone models. To create the application algorithm, a formula was developed to approximately map the color value from the smartphone images to the true value using a colorimeter. A basic validation was performed on 60 new samples covering a range of colors, followed by a field validation on 100 healthy dentate participants aged 20-39 years.

RESULTS

The intraclass correlation coefficient for two repeated shots had a high value ≥ 0.97 in the basic and field validations, confirming reliability. No significant differences were observed in the paired t-test and Wilcoxon signed-rank test, and a significant and strong correlation (correlation coefficient ≥ 0.92) was observed between the evaluation values using the colorimeter and the basic and field validations. Bland-Altman plots further confirmed the validity of the application.

CONCLUSIONS

A software application was developed to enable easy, quick, and accurate determination of the masticatory performance of a chewing gum from images taken using a smartphone with highly reliable and validated results.

Structural brain feature is associated with changes of masticatory performance in healthy elderly people: Evidence from longitudinal neuroimaging research over two years

BACKGROUND

Human neuroimaging studies have revealed the association between brain structure and masticatory function. However, the majority of the studies adopted a cross-sectional design, which hardly reveals the change in masticatory function and brain structure between different timepoints, and the dynamical association between changes in masticatory function and changes in brain structure has not been elucidated.

OBJECTIVE

With a longitudinal design, we assessed the association between changes in masticatory performance (MP) and regional brain volume.

METHODS

Twenty-two elderly participants received assessments of the number of missing teeth and MP (via colour-changeable chewing gum) when they entered the study (i.e. the initial stage, T0 ), approximately 6 months later (T0.5 ), and approximately 1-2 years later (T1 ). Difficulty of food intake was assessed using a questionnaire. The participants received magnetic resonance imaging (MRI) at T0 and T1 . The brain volume of the motor-related area was estimated using FreeSurfer for MRI data. The associations between different stages were analysed using Spearman's rho correlation coefficients.

RESULTS

(1) Individually, a smaller volume of right primary motor cortex at T0 was associated with increased MP from T0 to T1 , suggesting the brain's role in changing oral functions; (2) higher MP at T0 was associated with an increased volume of the left superior frontal cortex from T0 to T1 p, suggesting a potential effect on brain plasticity, and (3) increased difficulty to eat was associated with decrease MP but not brain volume of motor-related area.

CONCLUSIONS

The preliminary findings revealed a complicated pattern of structural brain features and masticatory function in elderly people, and either the hypothesis that the brain predisposes masticatory function or the hypothesis that mastication reshapes the brain is oversimplified.

Are demographic factors, masticatory performance and structural brain signatures associated with cognitive impairment in older people? A pilot study of cross-sectional neuroimaging data

BACKGROUND

The occurrence of cognitive impairment (CI) is expected to increase within an ageing population. CI is associated with tooth loss, which influences masticatory performance. A decrease in masticatory performance may cause functional and morphological changes in the brain. However, whether CI is associated with masticatory performance, demographics, and structural brain signatures has not been studied yet.

OBJECTIVES

To assess the associations between CI on the one hand, and masticatory performance, demographic factors, and structural brain signatures (i.e. cortical volume and thickness) on the other hand.

METHODS

In total, 18 older adults with CI (mean ± SD age = 72.2 ± 9.5 years) and 68 older adults without CI (65.7 ± 7.5 years) were included in this study. Masticatory performance was quantified using a colour-changeable chewing gum. A Magnetic Resonance Imaging (MRI) scan was used to map structural brain signatures. To study our aim, a multivariate binary logistic regression analysis with backward selection was performed.

RESULTS

The cortical volume of the right entorhinal cortex was negatively associated with CI (p < .01). However, demographic factors, masticatory performance, and the other structural brain signatures under investigation were not associated with CI.

CONCLUSION

A decrease in the volume of the right entorhinal cortex is associated with CI in older people.

Relationship between a gum-chewing routine and oral, physical, and cognitive functions of community-dwelling older adults: A Kashiwa cohort study

AIM

As associations between oral function and general health have been reported in community-dwelling older adults, easily implementable preventive measures are urgently required. We focused on the health benefits of gum chewing, as no studies have been carried out on the impact of gum-chewing routines on the health of older adults. This cross-sectional study aimed to determine whether the gum-chewing routine is associated with oral, physical and cognitive functions in community-dwelling older adults.

METHODS

This study included 1617 community-dwelling older participants in a health survey carried out in 2021. The gum-chewing routine and weekly chewing time were assessed using a self-administered questionnaire. The outcome measures, including actual measurements of oral function, physical function, cognitive function, dietary intake and lifestyle, were evaluated using self-administered questionnaires or health surveys.

RESULTS

We analyzed 1474 (mean age 76.1 ± 5.8 years, 45% women) participants for whom all data were not missing, and 14% of them had a gum-chewing routine for more than 30 min weekly. Oral functions were significantly higher in older adults with a gum-chewing routine, and there were substantially fewer participants with oral frailty (adjusted odds ratio 0.581, 95% confidence interval 0.340-0.993). Additionally, cognitive and physical functions, including grip strength, were significantly higher in the gum-chewing routine group.

CONCLUSIONS

Community-dwelling older adults with a gum-chewing routine have higher oral, physical and cognitive functions. These findings indicate that a gum-chewing routine might contribute to maintaining oral function and preventing frailty. Geriatr Gerontol Int 2024; 24: 68-74.

Chewing ability and associated factors in older adults in Germany. Results from GEDA 2019/2020-EHIS

BACKGROUND

Oral well-being is an important component of general well-being and quality of life, as it is greatly influenced by the ability to chew and speak, and thus by central factors of social interaction. Because quality of life and participation are important factors for health in older age, the aim of this article was to examine the chewing ability, including associated factors, for the older population in Germany on the basis of a nationally representative sample.

METHODS

Database is the German Health Update (GEDA 2019/2020-EHIS), a population based cross-sectional survey of the Robert Koch Institute. In the telephone interview, participants aged 55 years and older were asked: "Do you have difficulty biting and chewing on hard foods such as a firm apple? Would you say 'no difficulty', 'some difficulty', 'a lot of difficulty' or 'cannot do at all/ unable to do'?" Prevalences and multivariate prevalence ratios (PR) were calculated with 95% confidence intervals (95% CI) from log-Poisson regressions. Sociodemographic, health-, behavioral- and care-related characteristics were investigated as associated factors.

RESULTS

The analyses were based on data from 12,944 participants (7,079 women, 5,865 men). The proportion of people with reduced chewing ability was 20.0%; 14.5% had minor difficulty, 5.5% had major difficulty. There were no differences between women and men. The most important associated factors for reduced chewing ability were old age (PR 1.8, 95% CI 1.5-2.1), low socioeconomic status (PR 2.0, 95% CI 1.7-2.5), limitations to usual activities due to health problems (PR 1.9, 1.6-2.2), depressive symptoms (PR 1.7, 1.5-2.1), daily smoking (PR 1.6, 95% CI 1.3-1.8), low dental utilization (PR 1.6, 95% CI 1.4-1.9), and perceived unmet needs for dental care (PR 1.7, 95% CI 1.5-2.1).

CONCLUSIONS

One fifth of adults from 55 years of age reported reduced chewing ability. Thus, this is a very common functional limitation in older age. Reduced chewing ability was associated with almost all investigated characteristics. Therefore, its prevention requires a holistic view in the living environment and health care context of older people. Given that chewing ability influences quality of life and social participation, maintaining or improving chewing ability is important for healthy aging.

The relationships between mastication and cognitive function: A systematic review and meta-analysis

Masticatory function such as chewing is expected to modify human cognitive function, and/or the possibility of improving cognitive function is also predicted. This systematic review investigated whether masticatory function affects cognitive function for older/young adults. Full articles written in English from January 2000 to April 2022 were collected using PubMed and Cochrane Library. Target outcomes were cognitive function test scores, cognitive processing speed (reaction time), and masticatory function. For each research question, two independent reviewers conducted the search and screening, data extraction, quality assessment, and risk of bias assessment. The reviewers resolved any disagreements by discussion. From 226 articles retrieved, 20 were included in this review. Older adults with lower scores on the cognitive function test had lower masticatory performance, lower chewing ability, chewing difficulty, and decreased number of teeth. An increased risk of cognitive impairment was found in older adults with masticatory dysfunction. For young adults, gum chewing significantly reduced the processing speed of cognitive tasks compared to no gum chewing. Although most of the evidence included had a low level of evidence and a high risk of bias because of the research designs, the results still suggest that mastication may be a factor in improving cognitive function.

Lip and tongue strength associated with chewing patterns in aging population

BACKGROUND

Improving chewing function of older adults increases the health-related quality of life. Few studies indicated the correlation between tongue, lip strength on masticatory performance in older people. The study aimed to investigate the association between lip, tongue strength on chewing pattern in aging population.

METHODS

The older adults had independent daily intake without assistance were enrolled. They had intact dentition and no periodontitis. To estimate the number of chewing strokes and chewing time by consuming a cornstarch cookie were used to represent chewing pattern. Lip and tongue pressure were evaluated with an Iowa Oral Performance Instrument. Linear regression analysis was used to analyze the lip and tongue pressure associated with the chewing time and strokes. Spearman's correlation analysis was utilized to evaluate the associations among chewing time and chewing strokes or lip and tongue pressure.

RESULTS

35 women and 35 men with an average age of 73.2 years were investigated. Tongue pressure was significantly related to the chewing time and the number of chewing strokes (p = 0.01 and 0.03). There was a close association between chewing time and the number of chewing strokes (p < 0.0001). The correlation between lip and tongue pressure was significant (p < 0.0001).

CONCLUSION

The tongue strength significantly related to chewing ability in aging population. Increasing the tongue strength greatly reduced the number of chewing strokes and chewing time. Good masticatory ability could increase the motor function of tongue; raising the tongue strength might be able to improve mastication in older adults.

Lower masticatory function relates to cognitive health and intrinsic brain network in older adults

OBJECTIVES

Mastication is associated with brain activation at the primary somatosensory cortex (S1) and the primary motor cortex (M1). Masticatory functions differ between patients with cognitive impairment (CI) and cognitively healthy older adults (non-CI). The association between cognitive health, brain network of functional connectivity, and mastication has remained unknown. The study investigated the association between masticatory performance (MP) and the topological feature of the functional network at the M1 and S1 in the CI and non-CI groups.

SUBJECTS AND METHODS

Forty-nine non-CI and 15 CI subjects received resting-state (rs) fMRI and assessment of MP. The topological feature of the M1 and S1 was quantified by eigenvector centrality (EC), an index that reflects a brain region as a functional "hub" of brain network.

RESULTS

In the non-CI group, MP was significantly correlated with EC of the left M1 and the right M1. The correlation was not statistically significant in the CI group. Cognitive status (CI or non-CI) and EC of the left M1 and the right M1, respectively, were statistically significant predictors to individual MP.

CONCLUSION

Cognitive status and the topological feature of the M1 in the intrinsic functional network may contribute to the individual difference in masticatory function.

Pre-Adolescent Diet Normalization Restores Cognitive Function in Young Mice

Mastication is a fundamental function critical for human health. Controlled by the central nervous system (CNS), it influences CNS development and function. A poor masticatory performance causes cognitive dysfunction in both older adults and children. Improving mastication may prevent cognitive decline. However, no study has determined the period of masticatory dysfunction that impairs children's later acquisition of cognitive function. Herein, we developed an animal model wherein a soft diet was switched to a normal diet at early and late time points in young mice. We aimed to investigate the impact of restored mastication on learning and memory function. Behavioral studies were conducted to evaluate learning and memory. Micro-CT was used to evaluate orofacial structural differences, while histological and biochemical approaches were employed to assess differences in the hippocampal morphology and function. Correction to a hard-textured diet before adolescence restored mastication and cognitive function through the stimulation of neurogenesis, extracellular signal-regulated kinases, the cyclic adenosine monophosphate-response element-binding protein pathway, and the brain-derived neurotrophic factor, tyrosine receptor B. In contrast, post-adolescent diet normalization failed to rescue full mastication and led to impaired cognitive function, neuronal loss, and decreased hippocampal neurogenesis. These findings revealed a functional linkage between the masticatory and cognitive function in mice during the juvenile to adolescent period, highlighting the need for adequate food texture and early intervention for mastication-related cognitive impairment in children.

Kinematic Features of Mandibular Movement during Mastication in Geriatric Individuals Who Are Provided with a Dysphagia Diet at Long-Term Care Facilities

Providing a normal diet to a care recipient who is unable to form an adequate bolus may cause suffocation or aspiration pneumonia. We investigated whether differences in kinematic data of mandibular movements during mastication can be used as an indicator of the need for a dysphagia diet in the elderly in long-term care facilities. We included 63 participants who were provided with solid food in two long-term care facilities. The primary outcome variable was the kinematic data on mandibular movement during cracker chewing. The analysis results were compared between the normal and dysphagia diet groups. Logistic regression analysis and receiver operating characteristic curve analyses were performed. Significant differences were observed in the masticatory time, cycle frequency, total change amount, number of linear motions, and circular motion frequency between the normal and modified diet groups. The odds ratio for the circular motion frequency was -0.307, and the calculated cutoff value was 63%, with a sensitivity of 71.4%, a specificity of 73.5%, and an area under the curve of 0.714. Thus, these characteristics may be useful for detecting care recipients who need to be provided with a dysphagia diet. Moreover, the circular motion frequency could be used as a screening test to identify people who need a dysphagia diet.

Assessment of subjective and objective masticatory function among elderly individuals with mild cognitive impairment

BACKGROUND

Masticatory function is known to be related to cognitive ability; therefore, factors for improving masticatory function should be identified.

AIMS

This study aimed to identify factors influencing masticatory function associated with mild cognitive impairment (MCI) in elderly individuals.

METHODS

A total of 123 elderly participants [mean age: 76.5 ± 6.5 years; 82 females (66.7%), 41 males (33.3%)] were included. Cognitive function was evaluated by the Korean version of the Mini-Mental State Examination (KMMSE). Questionnaires for subjective evaluation were administered, and dynamic objective masticatory function evaluations, including chewing tests and bite force measurements, were performed. Intergroup differences were evaluated by the Wilcoxon rank-sum and chi-square test, and correlations between cognitive ability and masticatory function were evaluated by multilinear logistic regression.

RESULTS

The number of teeth, number of posterior teeth, bite force, masticatory ability index (MAI) and posterior support status showed significant differences between the normal (KMMSE > 23) and MCI (KMMSE ≤ 23) groups. However, only the MAI, representing dynamic masticatory performance, was significantly associated with MCI regardless of age, sex and removable prostheses. The number of teeth and posterior teeth, bite force, subjective masticatory ability and posterior occlusal support showed no significant association with MCI.

DISCUSSION

These results suggested the importance of chewing function for preventing the progression of cognitive impairment.

CONCLUSIONS

Considering that only the MAI was significantly associated with MCI, it is more important to improve chewing efficiency by harmonizing therapeutic prosthetics with the surrounding masticatory system than simply increasing the number of teeth to prevent or delay cognitive impairment in elderly individuals.

Associations Between Abdominal Obesity, Chewing Difficulty and Cognitive Impairment in Dementia-Free Chinese Elderly

OBJECTIVE

To investigate the independent and synergistic associations between abdominal obesity, chewing difficulty and cognitive impairment in a community-dwelling older adults sample in China.

METHODS

Cognitive function was measured by the 5 min- Montreal Cognitive Assessment (5 min-MoCA) and abdominal obesity was measured by A Body Shape Index (ABSI) in 572 participants recruited from local communities. Chewing difficulty was assessed via a self-report questionnaire. Linear regression and general logistic regression were performed to investigate the association of chewing difficulty and abdominal obesity with cognition.

RESULTS

Chewing difficulty score [β (95% CI) = -.30 (-.49, -.11)] and ABSI [β (95%CI) = -.30 (-.55, -.05)] were independently associated with worse performance on the 5 min-MoCA. Whilst ABSI was not associated with cognitive impairment, the co-existence of chewing difficulty and abdominal obesity [OR (95% CI) = 2.22 (1.18, 4.17)] was found associated with the presence of cognitive impairment.

CONCLUSION

Chewing difficulty and abdominal obesity were independently associated with cognition. Abdominal obesity and chewing may have an additive effect on cognitive function.

The Risk of Cardiovascular Disease According to Chewing Status Could Be Modulated by Healthy Diet in Middle-Aged Koreans

To assess whether a healthy diet could change the risk of cardiovascular disease (CVD)-related chewing difficulty (CD) in relation to age distribution. In a cross-sectional study of 9411 middle-aged Koreans from the KNHANES VII. In this study, the Framingham 10-year general CVD risk prediction equations and the Korean Heathy Eating index (KHEI) were used to assess the 10-year estimated risk of CVD and dietary quality, respectively. CD was experienced by 16.7% of the total subjects. Among subjects with CD, the 10-year estimated CVD risk was 8.71% of the subjects in the 30−49 years age group and 30.38% of those in the 50−64 years age group, which is a difference of approximately 3.5 times. Regardless of age distribution, the total score of the KHEI in subjects who had CD was significantly lower than in those who had no CD (NCD) (p = 0.004 for the 30−49 years age group and p < 0.001 for the 50−64 years age group, respectively). Among the subjects with poor KHEI in the 30−49-year age group, the adjusted odds ratio for the 10-year estimated CVD risk of the subjects with CD was 2.204-fold (95% CI = 1.385−3.506) higher using NCD as a reference. The findings showed that dietary quality could modify the risk for CVD according to chewing status.

Association between dietary hardness score and activities of daily living among individuals aged 90 years

Objectives

With the rapidly aging world population, Japan has many older people with difficulties in maintaining oral health. This study aimed to investigate the relationship between dietary hardness score and performance of activities of daily living (ADL) of 90‐year‐old individuals in rural areas of Japan.

Material and Methods

A total of 236 individuals (64 men and 172 women) aged 90 years in Mitsugi town, Hiroshima, Japan, were included. Assessment of oral status and survey of ADL were performed. The association of ADL with dietary hardness score and the number of remaining teeth was determined.

Results

The mean dietary hardness score was 8.3 ± 2.6. Eighty individuals showed independence in ADL, whereas 156 individuals showed dependence. Logistic regression analysis, adjusted for potential confounding factors, showed that dietary hardness score was associated with ADL status but not the number of remaining teeth.

Conclusion

Our findings suggest that a low dietary hardness score is associated with dependence on ADL in 90‐year‐old individuals.

Does reduced chewing ability efficiency influence cognitive function? Results of a 10-year national cohort study

A growing body of literature suggests that oral health can influence cognitive function during aging. However, it is currently unclear whether reduced masticatory efficiency influences cognitive impairment in longitudinal studies.This study sought to investigate the effects of reduced chewing ability on the incidence of cognitive impairment using national representative data from 10 years of follow-up in Korea. Among the 10,254 people recruited in 2006 (1st wave), 7568 with normal cognitive function were selected. The participants were followed up every 2 years. The number of participants followed up until the 6th wave was 5020 in 2016. Chewing ability and scores on the Mini-Mental State Examination were recorded using self-reported questionnaires. Risk factors for dementia taken from systematic literature reviews were used as covariates. We performed logistic regression and created general estimating equation models after controlling for all covariates to assess the relationship between chewing ability and cognitive decline. Decreased chewing function was associated with mild cognitive impairment after controlling for confounding variables.The odds ratio for cognitive impairment was about 1.28 times higher than in people with poor chewing function as in those with good chewing function. We identified changes in chewing function from the 1st wave to the 6th wave; the odds ratios were 2.21 (95% confidence interval = 1.90-2.58) in the good-poor group and 2.11 (95% confidence interval = 1.74-2.55) in the poor-poor group.We identified an impairment in cognitive function in the poor (poor-poor and good-poor) chewing ability group. Therefore, we have confirmed that reduced mastication efficiency may contribute to a deterioration in cognitive function. People with deteriorated chewing ability must be given additional attention to aid in the prevention of cognitive decline.

Associations of general health conditions with masticatory performance and maximum bite force in older adults: A systematic review of cross-sectional studies

OBJECTIVES

To give an overview of the current evidence on the associations of general health conditions with masticatory performance and maximum bite force in older adults.

DATA/SOURCES

Three electronic databases (Medline via PubMed, Embase via Ovid and CINAHL Plus via EBSCOhost) were searched up to September 2021 for cross-sectional studies on general health conditions and masticatory performance or maximum bite force in older adults. Methodological quality of the included studies was independently evaluated based on Joanna Briggs Institute critical appraisal checklist for analytical cross-sectional studies. Data on the associations between general health conditions and masticatory performance or maximum bite force were extracted.

STUDY SELECTION

Of the 5133 records identified, 39 studies (43 articles) were included in this review. Significant negative associations were found between masticatory performance and stroke, sarcopenia, amyotrophic lateral sclerosis, chronic obstructive pulmonary disease, dyspepsia, dysphagia, anorexia, and carotid atherosclerosis. Significant negative association was found between maximum bite force and sarcopenia. There were equivocal results on the association between masticatory performance and diabetes mellitus, and between maximum bite force and stroke, and amyotrophic lateral sclerosis. There was no significant association between masticatory performance and metabolic syndrome, and between maximum bite force and progress of Parkinson's disease. Most studies revealed positive associations of physical function with masticatory performance and maximum bite force.

CONCLUSIONS

Negative associations between masticatory function of older adults and presence of several systemic diseases have been reported in a number of studies while there are positive associations between masticatory function and some physical function indicators.

CLINICAL SIGNIFICANCE

This study provides valuable information on the association of masticatory function with general health, which draws clinicians' attention to the masticatory function of older adults who suffer from certain systemic diseases or physical dysfunction, and to the need to improve their masticatory ability to achieve healthy aging.

Impact of Masticatory Behaviors Measured With Wearable Device on Metabolic Syndrome: Cross-sectional Study

Background

It has been widely recognized that mastication behaviors are related to the health of the whole body and to lifestyle-related diseases. However, many studies were based on subjective questionnaires or were limited to small-scale research in the laboratory due to the lack of a device for measuring mastication behaviors during the daily meal objectively. Recently, a small wearable masticatory counter device, called bitescan (Sharp Co), for measuring masticatory behavior was developed. This wearable device is designed to assess objective masticatory behavior by being worn on the ear in daily life.

Objective

This study aimed to investigate the relation between mastication behaviors in the laboratory and in daily meals and to clarify the difference in mastication behaviors between those with metabolic syndrome (MetS) and those without (non-MetS) measured using a wearable device.

Methods

A total of 99 healthy volunteers (50 men and 49 women, mean age 36.4 [SD 11.7] years) participated in this study. The mastication behaviors (ie, number of chews and bites, number of chews per bite, and chewing rate) were measured using a wearable ear-hung device. Mastication behaviors while eating a rice ball (100 g) in the laboratory and during usual meals for an entire day were monitored, and the daily energy intake was calculated. Participants’ abdominal circumference, fasting glucose concentration, blood pressure, and serum lipids were also measured. Mastication behaviors in the laboratory and during meals for 1 entire day were compared. The participants were divided into 2 groups using the Japanese criteria for MetS (positive/negative for MetS or each MetS component), and mastication behaviors were compared.

Results

Mastication behaviors in the laboratory and during daily meals were significantly correlated (number of chews r=0.36; P<.001; number of bites r=0.49; P<.001; number of chews per bite r=0.33; P=.001; and chewing rate r=0.51; P<.001). Although a positive correlation was observed between the number of chews during the 1-day meals and energy intake (r=0.26, P=.009), the number of chews per calorie ingested was negatively correlated with energy intake (r=–0.32, P=.002). Of the 99 participants, 8 fit the criteria for MetS and 14 for pre-MetS. The number of chews and bites for a rice ball in the pre-MetS(+) group was significantly lower than the pre-MetS(–) group (P=.02 and P=.04, respectively). Additionally, scores for the positive abdominal circumference and hypertension subgroups were also less than the counterpart groups (P=.004 and P=.01 for chews, P=.006 and P=.02 for bites, respectively). The number of chews and bites for an entire day in the hypertension subgroup were significantly lower than in the other groups (P=.02 and P=.006). Furthermore, the positive abdominal circumference and hypertension subgroups showed lower numbers of chews per calorie ingested for 1-day meals (P=.03 and P=.02, respectively).

Conclusions

These results suggest a relationship between masticatory behaviors in the laboratory and those during daily meals and that masticatory behaviors are associated with MetS and MetS components.

Trial Registration

University Hospital Medical Information Network Clinical Trials Registry R000034453; https://tinyurl.com/mwzrhrua

Effects of oral exercise on tongue pressure in Taiwanese older adults in community day care centers

Background/purpose

Oral exercise is a training method for swallowing dysfunction in older adults. The study investigated the effect of oral exercise on tongue pressure in older adults in Taiwanese community day care centers over a 3-month period.

Materials and methods

Participants over age 50 who were able to communicate and participating for the duration of the 12-week period were recruited from five community day care centers. A 15-min weekly group oral exercise activity was conducted. The tongue pressures were measured and multivariable linear regression models were used to assess the effect of oral exercise intervention on the participants’ tongue pressures.

Results

A total of 66 older adult participants, among whom the mean age was 78.06 ± 10.74 years. Tongue pressure continued improving during the intervention period, and the mean tongue pressure at the end of the study was 20.63 ± 10.45 kPa, which was significantly higher than the baseline measurement (16.92 ± 10.62 kPa, p < 0.001). Participants exhibited significant improvement in tongue pressure regardless of their age groups. Moreover, participants with one to seven pairs of functional tooth units (FTUs) exhibited significantly more improvement in tongue pressure (16.00 kPa, 95% CI = 2.58–29.43) than those without FTUs (p = 0.021).

Conclusion

Oral exercise over a 3-month period significantly improved tongue pressure among the study participants regardless of their gender or age group. Oral exercise should be integrated into comprehensive health promotion programs to assist in the improvement and maintenance of oral function among older adults.

Masticatory performance and other oral functions in community-dwelling elderly patients without posterior occlusal support by natural teeth

PURPOSE

To evaluate masticatory performance (MP), maximum occlusal force (MOF), maximum tongue pressure (MTP) and oral diadochokinesis (ODK) among community-dwelling elderly patients without posterior occlusal support.

METHODS

This study enrolled community-dwelling elderly patients (≥65 years old) who belonged to Eichner A, B4, C1, C2, and C3. Each oral function was statistically compared among groups. Correlations between MP and other variables were examined in Eichner B4 and C patients.

RESULTS

MP and MOF values in Eichner B4 and C patients were significantly lower than in Eichner A patients. There were significant differences in MTP values between Eichner "A and C2, C3", and "B4 and C2, C3". ODK in Eichner C patients showed significantly lower values compared to Eichner A patients in general. Although there were statistically significant correlations of MP with age, the number of remaining teeth and all oral functions were identified, and multiple regression analysis indicated that MOF and MTP were independently related to MP.

CONCLUSION

Oral functions in Eichner B4 and C patients were lower compared to Eichner A patients. MP was significantly correlated with MOF and MTP in elderly patients without posterior occlusal support, suggesting the importance of rehabilitation of MOF and MTP in MP.

Chewing function and related parameters as a function of the degree of dementia: Is there a link between the brain and the mouth?

Background

To date, no study has investigated the association between chewing function and related parameters as a function of the degree of dementia using a finer subdivision of the values of the Mini‐Mental State Examination (MMSE).

Objective

This study aimed to investigate the differences in chewing function and related parameters as a function of the degree of dementia.

Methods

An analysis of cross‐sectional data obtained from the OrBiD (Oral Health, Bite Force, and Dementia) pilot study was performed. The participants were stratified into five groups based on the outcomes of the MMSE (no dementia, MMSE 28–30; mild cognitive impairment, MMSE 25–27; mild dementia, MMSE 18–24; moderate dementia, MMSE 10–17; severe dementia, MMSE <10). The chewing efficiency, maximum occlusal force and related parameters (number of supporting zones, number of teeth, Eichner index, tooth/denture status, denture quality, and dental treatment needs) were recorded.

Results

The MMSE groups showed significantly different chewing efficiencies (p = .003, Jonckheere‐Terpstra test) and maximum occlusal forces (p = .003, Jonckheere‐Terpstra test), but the number of supporting zones (p = .055, chi‐square test) and the number of natural teeth (p = .126, chi‐square test) were not different. The Eichner index, tooth/denture status, denture quality and dental treatment need showed no significant associations with the degree of dementia.

Conclusion

An improvement in the usability of the measurement methods for assessing chewing function in people with dementia is needed. Research involving people with dementia is necessary because the nutritional situation often deteriorates rapidly within a multifactorial system, which includes chewing ability and oral health.

Cognitive changes and neural correlates after oral rehabilitation procedures in older adults: a protocol for an interventional study

BACKGROUND

Epidemiological studies show an association between masticatory function and cognitive impairment. This has further strengthened the notion that tooth loss and impaired masticatory function may be risk factors for dementia and cognitive decline. Animal experiments have indicated a causal relationship and several possible mechanisms have been discussed. This evidence is, however, lacking in humans. Therefore, in the current interventional study, we aim to investigate the effect of rehabilitation of masticatory function on cognition in older adults.

METHODS

Eighty patients indicated for prosthodontic rehabilitation will be randomly assigned to an experimental or a control group. Participants will conduct neuropsychological assessments, masticatory performance tests, saliva tests, optional magnetic resonance imaging, and answer questionnaires on oral health impact profiles and hospital anxiety and depression scale before, 3 months, and 1 year after oral rehabilitation. The difference between the two groups is that the control group will be tested an additional time, (at an interval of about 3 months) before the onset of the oral rehabilitation procedure. The primary outcome is a change in measures of episodic memory performance.

DISCUSSION

Although tooth loss and masticatory function are widespread in older people, it is still an underexplored modifiable risk factor potentially contributing to the development of cognitive impairment. If rehabilitation of masticatory function shows positive effects on the neurocognitive function, this will have great implications on future health care for patients with impaired masticatory status. The present project may provide a new avenue for the prevention of cognitive decline in older individuals.

TRIAL REGISTRATION

The protocol for the study was retrospectively registered in ClinicalTrials.gov Identifier: NCT04458207, dated 02-07-2020.

How Do Changes in Oral Health and Chewing Efficiency Affect the Changes of Oral-Health-Related Quality of Life of Nursing-Home Residents in the Short Term?

Objective

To evaluate how changes in oral health and chewing efficiency affect the changes in oral-health-related quality of life (OHRQoL) of nursing-home residents over six months.

Methods

The study was conducted in nine nursing homes. Sociodemographic and general data were collected for all eligible individuals (n = 150). Of these, 114 participants (mean age 82.0 [± 9.5] years, 77.2% women) were available for the following tests at baseline and six months later: a comprehensive examination of dental and general health, a two-colour mixing-ability test (to assess chewing efficiency), the Geriatric Oral Health Assessment Index (GOHAI; to evaluate the OHRQoL), and the Mini Mental State Examination (MMSE; to diagnose the presence and severity of dementia). Univariate and multivariate linear regression models were compiled to analyse possible factors affecting OHRQoL.

Results

For the final analysis, 108 participants were available. For the study cohort as a whole, a decrease in the number of functional occluding pairs (C: 0.195; p = 0.034) and an increase in dental-treatment needs (C: −1.968; p = 0.056) had the greatest negative effects on OHRQoL as expressed by the GOHAI score. For denture wearers, a deterioration of denture condition (C: −2.946; p = 0.003) was the most important predictor for a decline in OHRQoL.

Conclusion

A short-term decline in oral health and function affects the OHRQoL of nursing-home residents. The most important dental variables in this regard are the number of functional occluding pairs and dental and denture-related treatment needs.

Oral Health Status and Nutritional Habits as Predictors for Developing Alzheimer's Disease

OBJECTIVE

Poor oral health, mainly tooth loss, has been suggested to pose a risk factor for Alzheimer's disease (AD). The nature of this relationship can be explained by mastication deficit and nutritional status. Also, the influence of nutritional parameters on cognitive impairment has been documented. The aim of this study was to investigate whether poor dental status and nutrition habits can be potential separate or associated risk factors for development of the AD.

METHODS

The study sample included 116 patients with AD and 63 controls. Sociodemographic variables were investigated as factors potentially associated with AD. Dental examination included recording the number of natural teeth, presence of fixed or removable dentures, and the number of functional tooth units (FTUs). Nutritional status analysis included qualitative nutrition information, body mass index, serum albumin level, food consistency, and need for assistance in feeding. Regression analysis was used to investigate the predictors for development of AD.

RESULTS

Variables with significant differences between groups, which were analyzed by using the binary regression analysis, were marital status, residence, number of total FTUs (no matter whether the contacts were between natural teeth or dentures), eating meat/fish and fruits/vegetables, food consistency, and serum albumin level. Logistic regression analysis showed that being single/widowed/divorced, eating more meat/fish or fruit/vegetable, eating blended/mashed/liquid food, having low levels of serum albumin, and having less FTUs were significant predictors for developing dementia.

CONCLUSION

Having fewer occlusal contacts, consumption of soft food, and lower serum albumin levels can be considered as associated risk factors for AD.

Food consumption frequency of Korean adults based on whether or not having chewing difficulty using 2013-2016 KNHANES by sex-stratified comparative analysis

BACKGROUND/OBJECTIVES

This study examined the associations between food consumption frequency of Korean adults and self-perceived chewing difficulty, using the food frequency questionnaire (FFQ, 112 items) from 2013-2016 of the Korea National Health and Nutrition Examination Survey (KNHANES).

SUBJECTS/METHODS

Subjects were divided into not difficult in chewing (NDC) and difficult in chewing (DC) groups, with 24.17% being classified into DC. Males and females consumed 35 and 37 items less frequently than the other sex, respectively. Due to the remarkable sex difference in food consumption, sex-stratified one-sided survey regression analysis was performed after adjusted for the effect of age, household income, and self-rated health status.

RESULTS

Thirty-four items of FFQ were significantly less consumed by the DC group. Females exclusively consumed less beverages and alcohol while males showed the same for fruits and milk·dairy products. Consumption frequency of 8 items such as steamed potatoes·grilled potatoes, stir fried beef, other kimchi·fresh vegetable kimchi, orange, sour pork·pork cutlet, tteokbokki and green tea were significant only in males. In contrast, 17 items including cooked rice with other grains and legumes, boiled egg·steamed egg, Korean cabbage kimchi, banana, and tofu stew·soft tofu stew were significant only for females. Finally, items that showed significance for both were 9 items including loaf bread, ready-to-eat cereal, steamed sweet potatoes·grilled sweet potatoes, stir-fried lotus roots·stir-fried burdock, green laver salad·brown seaweed salads, apples, tomato·cherry tomatoes, squid (raw, dried shredded, boiled, stir-fried), and curd type yogurt.

CONCLUSIONS

Findings in this study suggest chewing difficulty may be an important nutritional issue that has to be dealt with for healthful food consumption, with distinct interest of sex.

A multilevel analysis of the importance of oral health instructions for preventing tooth loss: The 8020 Promotion Foundation Study of Japanese Dental Patients

Background

Many studies have reported risk factors for tooth loss. Oral health instruction is considered effective at improving oral health behavior and oral health. However, few studies have examined the relationship of dental clinic factors, such as the number of dental hygienists and implementation of oral health instructions, with tooth loss. Here, we conducted a multilevel analysis to clarify the dental clinic risk factors associated with tooth loss.

Methods

Baseline surveys were conducted at 1216 dental clinics in 46 prefectures in Japan, and 12,399 dental patients aged 20 years and over underwent oral examinations and completed a questionnaire. The dental clinics also completed a questionnaire at baseline. A 3-year follow-up survey included 2488 patients in 585 dental clinics. Multilevel multivariate logistic regression analysis was used to examine the risk of tooth loss at the patient and clinic levels.

Results

Of the patient variables, older age, higher mean probing pocket depth, current or past smoking, and bleeding during tooth brushing were associated with higher risks of tooth loss. Individuals with many teeth who visited dental clinics for maintenance were at significantly lower risk of tooth loss. Of the clinic variables, patients attending dental clinics with four or more dental hygienists had a significantly lower risk of tooth loss (OR 0.68, 95% CI 0.50–0.99). Patients attending dental clinics that provide oral health instructions for 20 min or more had a significantly lower risk of tooth loss (OR 0.69, 95% CI 0.50–0.96).

Conclusions

In addition to individual risk factors for tooth loss, dental clinic factors such as length of oral health instruction and number of dental hygienists are associated with tooth loss. In dental clinics, ensuring sufficient time for dental hygienists to provide oral health instructions can help prevent tooth loss in dental patients.

The Effects of Dental Status and Chewing Efficiency on the Oral-Health-Related Quality of Life of Nursing-Home Residents

Objective

The aim of this study was to evaluate the effects of dental status and chewing efficiency on the oral-health-related quality of life (OHRQoL) of nursing-home residents.

Materials and Methods

The study was conducted in nine nursing homes. All eligible participants were included, and general and medical data, information about nutritional status and their dental and prosthetic status were collected. Chewing efficiency was assessed by means of a two-colour mixing-ability test. The simple count version of the Geriatric Oral Health Assessment Index (SC-GOHAI) was used to evaluate participants’ OHRQoL, and the Mini-Mental State Examination to classify the presence of cognitive impairment. Univariate and multivariate regression models were used to analyse data.

Results

The mean age of the participants was 82.1 (± 9.8) years and most participants suffered from at least very mild cognitive impairment. OHRQoL for all participants (n = 143) and denture wearers only (n = 105) was substantially associated with the type of prosthesis, the presence of natural teeth, the number of functional occluding pairs and dental and denture-related (if applicable) treatment needs. Furthermore, in both model’s univariate analysis showed that chewing efficiency also affected OHRQoL. In contrast, multivariate analysis of all participants revealed that only a higher number of functional occluding pairs (C: 0.250; p < 0.001), fewer dental treatment needs (C: −1.733; p = 0.019) and a better nutritional status (C: −1.298; p = 0.048) were relevant for better OHRQoL. For denture wearers, a higher number of functional occluding pairs (C: 0.192; p = 0.011), a better denture condition (C: −2.194; p= 0.003) and a higher body mass index (BMI) (C: 0.145; p = 0.006) were the main variables associated with better OHRQoL among participants.

Conclusion

Good oral health and oral function, including chewing efficiency, are associated with a high OHRQoL of nursing-home residents. However, few dental treatment needs, well-fitting dentures without treatment needs and a high number of functional occluding pairs seem to be the principal variables for an acceptable OHRQoL of nursing-home residents.

Chewing Efficiency, Global Cognitive Functioning, and Dentition: A Cross-sectional Observational Study in Older People With Mild Cognitive Impairment or Mild to Moderate Dementia

Introduction: Previous studies suggest an association between poor mastication and cognitive impairment. The role of chewing efficiency and dentition in this relation is unclear. The aim was to examine global cognitive functioning and dentition as predictors for chewing efficiency, in older people with mild cognitive impairment (MCI) or dementia.

Methods: In this observational cross-sectional study, 136 people with MCI or dementia were included. The chewing efficiency was assessed with a two-colored chewing gum and analyzed with the Chewing Efficiency Analysis software. The level of global cognitive functioning was measured with the Mini Mental State Examination (MMSE) by trained clinical staff. An oral examination was performed by a dentist and included the number of present teeth, the number of occluding pairs, and the presence of prostheses. Age, gender, and educational years were derived from the medical records. Univariate and multivariate backward stepwise linear regression analyses were used to evaluate global cognitive functioning and dentition as predictors for chewing efficiency.

Results: The mean age of the participants was 82.1 (SD 5.8) years, and 74 (54.4%) were female. The participants had a median MMSE score of 22.4 (IQR 18.0–26.0) and a median Chewing Efficiency Analysis score of 0.46 (IQR 0.14–0.59). The median number of teeth was 13.0 (IQR 0.0–23.0), and the median number of occluding pairs was 0.0 (IQR 0.0–7.0). Sixty-four (47.4%) of the participants wore full prosthesis in the upper jaw. In univariate linear regression analyses, predictive factors for the Chewing Efficiency Analysis score were age, MMSE score, full prosthesis in the upper jaw, number of present teeth, and number of occluding pairs. In the multivariate model, full prosthesis in the upper jaw and number of occluding pairs were significant predictors for the Chewing Efficiency Analysis score. Participants with full prosthesis in the upper jaw had a lower Chewing Efficiency Analysis score than participants with natural dentition in the upper jaw.

Conclusion: Better mastication is associated with a higher number of occluding pairs. Full prosthesis in the upper jaw is related to a lower chewing efficiency. Global cognitive functioning is not associated with mastication in older people with MCI or mild-to-moderate dementia. This might be explained by sufficient capacity for compensation of reduced mastication in this group.

Poor oral health conditions and cognitive decline: Studies in humans and rats

Background

The relationship between poor oral health conditions and cognitive decline is unclear.

Objective

To examine the association between oral health and cognition in humans and rats.

Methods

In humans: a cross-sectional study was conducted. Cognitive levels were evaluated by the Mini Mental State Examination (MMSE); oral conditions were reflected by the number of missing index teeth, bleeding on probing, and probing pocket depth (PD). In rats: a ligature-induced (Lig) periodontitis model and Aβ_25-35-induced model of Alzheimer’s disease (AD) were established; tumor necrosis factor-α (TNF-α), interleukin 1 (IL-1), interleukin 6 (IL-6), and C-reactive protein levels in the hippocampus and cerebral cortex were detected.

Results

MMSE scores for the number of missing index teeth ≥ 7 group were significantly lower than those in the ≤ 6 group. A negative relationship (correlation coefficient ρ = −0.310, P = 0.002) was observed between MMSE scores and number of missing index teeth. More missing index teeth and lower education levels were independent risk factors for cognitive decline. A negative relationship (correlation coefficient ρ = −0.214, P = 0.031) was observed between MMSE scores and average PD. TNF-α and IL-6 levels in the hippocampus of the Lig+AD group were significantly higher than those of the AD group. IL-1 and IL-6 levels in the cerebral cortex of the Lig+AD group were significantly higher than those of the AD group.

Conclusion

Poor oral health conditions including more missing index teeth and higher average PD may be risk factors for cognitive decline. Periodontitis may increase inflammatory cytokines in rat models of AD.

Do subjectively and objectively impaired oral health parameters influence geriatric assessment results in hospitalized geriatric patients?

BACKGROUND

Impaired oral health affects oral health-related quality of life (OHrQoL) in orthogeriatric hospitalized patients, and both might be associated with potential risk factors for functional impairment, based on the comprehensive geriatric assessment (CGA) and related blood laboratory values. As data on this field are scarce, we investigated possible associations between oral health, items of the geriatric oral health assessment instrument (GOHAI), CGA assessment tools, and relevant laboratory values.

METHODS

Explorative cross-sectional pilot study investigating oral and general health, OHrQoL, and functionality based on objective oral health, GOHAI, CGA, and routinely assessed laboratory parameters of orthogeriatric patients. Correlations (Spearman's rho and Pearson's) and regression analysis were performed for the dependent variables functionality, cognition, Mini-Nutritional Assessment, Falls Efficacy Scale (FES), and the 15-item geriatric depression scale (GDS).

RESULTS

Among all participants (N = 40), several GOHAI single items (GOHAI 1,4,5,7,10,11) correlated with certain CGA assessment results (fear of falling, Barthel index, handgrip power). Reduced subjective oral health (GOHAI, xerostomia) and objective oral health (oral hygiene index, root caries index, unstimulated salivation rate) correlated with reduced general health and CGA results (polypharmacy, handgrip power, FES, GDS). Anemia was seen in all participants, but no associations between reduced oral health and laboratory blood values were detected.

CONCLUSION

Our results demonstrate the association between impaired subjective and objective oral health, OHrQoL, and physical functional impairment among orthogeriatric patients. Impaired GOHAI item results at the dentist, and the association between GOHAI values and CGA results that implies an association between physical and oral health, should encourage a geriatric check based on CGA, and vice versa. Results encourage interdisciplinary cooperation between geriatricians and dentists, but also indicate the need for further research in this field.

TRIAL REGISTRATION

DRKS00013230.

Can chronic oral inflammation and masticatory dysfunction contribute to cognitive impairment?

PURPOSE OF REVIEW

This article provides an overview of current literature focused on oral health and cognitive impairment in older adulthood, focusing in particular on whether oral inflammation, tooth loss and masticatory dysfunction might increase the risk of cognitive impairment in this age group.

RECENT FINDINGS

There is now general acceptance that cognitive impairment contributes to poor oral health, largely through detrimental changes in behaviours related to maintaining good oral hygiene. There is more limited evidence for the reverse causal direction, but at least some studies now suggest that inflammatory mechanisms, tooth loss and masticatory dysfunction each have the potential to contribute to cognitive decline.

SUMMARY

Poorer oral health significantly correlates with cognitive dysfunction, and at least some studies suggest that there may be a bi-directional causal relationship. Randomized controlled trials assessing cognitive abilities in relation to oral hygiene or oral health interventions, or provision of removable or fixed (implant-supported) dentures, are encouraged.

Improvements in oral functions of elderly after simple oral exercise

Purpose: Conventional oral exercises in previous studies are considered impractical for continuous use in the elderly because of the extended duration needed for effective outcomes. Therefore, in the present study, a simple oral exercise (SOE) was developed to reduce performance time, focusing on improvements in mastication, salivation, and swallowing functions. The aim of this study was to determine the short-term effects of the SOE with respect to improving mastication, salivation, and swallowing function in elderly subjects ≥65 years of age.

Patients and methods: The study included 84 subjects, all of whom performed the SOE 2 times per day for 1 week. Masticatory performance was assessed using the mixing ability index (MAI). Unstimulated saliva and the degree of moisture of the tongue/buccal mucosa were evaluated, and the repetitive saliva swallowing test was performed. On the basis of each of these four measurements, subjects were dichotomized into two groups with high (good) and low (poor) conditions. The same evaluations were conducted before and immediately after intervention, as well as after 1 week of intervention. A subjective evaluation with questionnaires was performed after 1 week of intervention. The changes were analyzed using repeated-measures ANOVA, Cochran’s Q test, and McNemar’s test.

Results: The mean MAI increased by 6% immediately after the intervention, and by 16% in the poor-chewing group. Similarly, the amount of unstimulated saliva increased by 0.1 ml/min immediately after the SOE, and by 29% in the poor-salivation group. The degree of tongue moisture increased by 3% and was maintained. In the poor-swallowing group, 25% and 40% of the subjects were upgraded to the good-swallowing group immediately after intervention, as well as after 1 week of intervention, respectively. The subjects experienced less discomfort as their oral function improved.

Conclusion: The SOE was effective in immediately improving oral functions, and improvement was maintained for 1 week.

Rehabilitation of lost teeth related to maintenance of cognitive function

OBJECTIVE

As the era of aging comes, cognitive impairment (CI) is increasing. The impact of rehabilitation of lost tooth on CI remains unclear. This study aimed to investigate whether non-rehabilitated lost teeth (NRLT) is associated with CI among Korean elders.

METHODS

A total of 280 elders comprising of 140 cases and 140 age-sex-matched controls were included in this cross-sectional study. CI was assessed using the Mini-Mental Status Examination (MMSE). NRLT was evaluated using panoramic radiograph and oral examination. NRLT was categorized into low (≤4) and high (≥5). Age, sex, education, drinking, smoking, exercise, obesity, hypertension, subclinical atherosclerosis, glucose, cholesterol, depression, and denture-wearing were considered as confounders. Conditional multivariate logistic regression analysis was applied to assess the adjusted association.

RESULTS

NRLT was associated with increased CI after controlling for confounders (odds ratio [OR] = 1.06, 95% confidence interval [95% CFI]: 1.00-1.13). However, lost teeth were not associated with CI. Those with high NRLT (≥5) compared to those with low NRLT (≤4) was more likely to have CI by 2.7 times (OR = 2.74, 95% CFI = 1.28-5.86).

CONCLUSION

Our data showed that NRLT was independently associated with CI. Hence, rehabilitation of the lost teeth could be important for the maintenance of cognitive function.

A 2-year longitudinal study of the relationship between masticatory function and progression to frailty or pre-frailty among community-dwelling Japanese aged 65 and older

BACKGROUND

An association has recently been reported between frailty and reduced masticatory function; however, the causal relationship remains unclear.

OBJECTIVE

The aim of this study was to clarify the relationship between masticatory function and frailty progression.

METHODS

Among 6699 individuals aged 65 and older (mean age 72.8 ± 5.2 years) who were invited to participate in comprehensive medical check-ups, 418 who underwent examinations at the Tokyo Metropolitan Institute of Gerontology in both 2013 and 2015 and who met inclusion criteria were included in this study. Frailty was determined with the Kihon Checklist developed by the Japanese Ministry of Health, Labour and Welfare. The following three masticatory functions were evaluated: occlusal force, mixing ability and subjective chewing ability. The following confounding factors were investigated: age, sex, grip strength, comfortable walking speed, Mini-Mental State Examination (MMSE) score, Self-Rating Depression Scale (SDS) score, skeletal mass index (SMI), number of medications taken and number of remaining teeth. Statistical analysis was performed with binomial logistic regression analysis.

RESULTS

Logistic regression analysis revealed that comfortable walking speed, SDS score, MMSE score and masticatory function were significantly related to progression to frailty or pre-frailty. Of the three masticatory function items evaluated, mixing ability and subjective chewing ability were related to frailty progression.

CONCLUSION

Our results confirm that masticatory function was associated with the progression to pre-frailty or frailty among community-dwelling individuals 65 years and older over the 2-year period of this longitudinal study. Of the masticatory function items evaluated, mixing ability and subjective chewing ability were associated with frailty progression.

Does reduced mastication influence cognitive and systemic health during aging?

There is a growing body of literature which suggests that oral health and mastication can influence cognitive and systemic health during aging. However, it is currently unclear whether oral health, masticatory efficiency, cognitive health and systemic health merely deteriorate independently with age, or whether mechanisms exist linking mastication to cognitive and systemic health directly. The aim of this paper is to review the extent to which reduced mastication influences cognitive and systemic health during aging because this knowledge may underpin future interventions that improve quality of life. Current evidence suggests that a deterioration in mastication and oral health during aging can have: 1) direct effects on systemic health through mechanisms such as the migration of the oral microbiota into the systemic environment, and 2) indirect effects on systemic health through changes nutrient intake. A loss of teeth and reduction in masticatory efficiency during aging can have: 1) direct effects on cognitive performance and potentially impact cognitive health through mechanisms such as enhanced adult hippocampal neurogenesis, and 2) indirect effects on cognitive health through changes in nutrient intake. It is concluded that oral health and masticatory efficiency are modifiable factors which influence the risk poor cognitive and systemic health during aging, although it is currently premature to propose chewing-based interventions to slow the rate of cognitive decline and improve cognitive health during aging. Future research should include large-scale longitudinal studies which control for the types of confounding factors which concurrently influence the association between mastication and cognitive and systemic health.

Revisiting the link between cognitive decline and masticatory dysfunction

Age-related decline in cognitive functions and dementia are major challenges in geriatric healthcare. Accumulating evidence from clinical, epidemiological and animal research suggests that tooth loss may be a risk factor for the decline of cognitive functions. This issue highlights the role of the brain-stomatognathic axis in geriatric medicine. Whether input from the stomatognathic apparatus can affect the brain remains an open debate. By revisiting the evidence published in the past five years, we argue that the hypothesis regarding the association between cognitive decline and masticatory dysfunction should be carefully interpreted. Most of the available clinical and epidemiological studies present only cross-sectional data. With respect to the prospective studies, important confounding factors, such as nutritional and physical conditions, were not fully controlled for. Animal research has revealed that hippocampal deficits may play key roles in the observed cognitive decline. However, experimental intervention and outcome assessments may not capture the condition of human subjects. Brain neuroimaging research may be suitable for bridging the gap between clinical and animal research, potentially contributing to (a) the clarification of the brain network associated with mastication, (b) the identification of brain imaging markers for exploring the mechanisms underlying long-term changes in masticatory functions, and (c) the elucidation of interactions between mastication and other cognitive-affective processing systems. Three potential models of the brain-stomatognathic axis and relevant hypotheses are summarized, focusing on the sensory feedback mechanisms, the compensation of motor control, and cerebellar deficits. Finally, we highlight four critical aspects of study and experimental design that should be considered in future research: (a) the refinement of the considered behavioral assessments, (b) the inclusion of baseline changes in mental and physical conditions,