Oral health and healthy chewing for healthy cognitive ageing: A comprehensive narrative review

Social context matters: Neighborhood environment as a moderator of the longitudinal relationship between edentulism and cognitive function among older adults in the United States

BACKGROUND

Previous research has shown poor oral health and neighborhood environment are both risk factors for cognitive decline among older adults. Little research has assessed the synergistic effects of poor oral health and neighborhood environment on cognitive health. This study examined whether neighborhood environment moderates the relationship between edentulism and cognitive function over time.

METHODS

Using data from the Health and Retirement Study, we analyzed 9,994 adults aged 60 and older with 39,976 person-wave observations over 14 years (2006-2020). Cognitive function was measured using the modified Telephone Interview for Cognitive Status. Edentulism status was self-reported complete tooth loss. Neighborhood environment included perceived neighborhood cohesion and disorder. We used linear mixed-effect models to examine the moderation effect of neighborhood environment on the association between edentulism and cognitive function over time.

RESULTS

Edentulous participants (22.4 %) showed an accelerated decline over time in cognitive function compared to dentate participants (β = -0.57, 95 % CI: -0.98, -0.16). The analysis revealed that neighborhood cohesion moderated the relationship between edentulism and cognitive function over time (β = 0.08, 95 % CI: 0.01, 0.15). Specifically, among individuals reporting higher neighborhood cohesion, the negative effect of edentulism on cognitive decline was attenuated. Neighborhood disorder had no significant associations with cognitive function.

CONCLUSIONS

This study demonstrates the relationship between edentulism and cognitive function varies by levels of neighborhood cohesion. The findings highlight the significance of neighborhood context in understanding the relationship between oral health and cognitive aging and suggest interventions addressing community environment may be particularly relevant for older adults with oral health challenges.

Trajectory of Cognitive Decline Across Different Racial/Ethnic Groups: The Role of Edentulism

This study examines whether age-related cognitive decline varies by race/ethnicity and how edentulism moderates these effects. Data from the Health and Retirement Study (2006-2020), including 23,669 respondents aged 51 and above across 189,352 person-wave observations were analyzed. Of all respondents, 13.4% were edentulous at baseline, with 65.4% identified as non-Hispanic White, 20.5% non-Hispanic Black, and 14.18% Hispanic. Results from linear mixed-effect models indicated that compared to non-Hispanic Whites, Hispanic and non-Hispanic Black participants exhibited lower baseline cognition scores but slower cognitive decline with age. For edentulous Hispanic participants, this slower rate of decline was attenuated by 0.03 units per year (95% CI: -0.06, -0.01, p = .049). The findings highlighted the need for targeted interventions and policies to improve oral health, particularly for Hispanic populations. Addressing oral health disparities could help mitigate cognitive decline in this group and reduce cognitive health disparities across racial/ethnic groups.

Influence of masticatory function on food preferences and cognitive performance in centenarians: an observational study

INTRODUCTION

Demographic projections forecast that centenarians' population growth will continue. "CaT: Centenari a Trieste" is an ongoing study featuring the collection of demographic and anamnestic data, including the analysis of oral variables.

AIMS

evaluate of the possible influence of past food preferences, taste perception and masticatory function on current cognitive status in a cohort of centenarians.

DESIGN

Observational transversal study.

MATERIALS AND METHODS

31 participants with mean age 102 ± 2 performed an examination of the oral cavity including the measurement of DMFT (Decayed Missing Filled Teeth), FTUs (functional teeth units), FOUs (functional occlusal units) and 6-n-propylthiouracil (PROP) taste perception assay. Results were correlated with dementia, subjective perception of oral health and food preferences.

RESULTS

Masticatory function did not correlate with dementia but had a significant impact on oral health perception. When analyzing variables affecting food preferences, PROP taste perception profile and DMFT resulted significantly correlated. Early edentulism didn't show to affect past dietary preferences.

CONCLUSIONS

our data suggest that in centenarians masticatory function doesn't seem to correlate to cognitive function, but influences the self-perception of oral health. Such results are an interesting addition to knowledge on the topic as they refer to a population which has never been considered before.

Functional significance and welfare implications of chewing in dogs (Canis familiaris)

Dogs chew on both nutritive and non-nutritive items as part of their food acquisition, ingestive behaviour, self-care, and social interactions. Various definitions distinguish chewing from related oral activities, such as gnawing, masticating, and biting. Surprisingly, despite chewing being a ubiquitous behaviour in dogs, its relevance to a dog's comfort, health, and purpose remains unclear. Additionally, the risk of dental fractures or other injuries may lead veterinarians to advise against feeding bones to dogs. This article explores the literature on chewing in dogs through the ethological framework of "Tinbergen's Four Questions" and the Five Domains framework for animal welfare assessment. Evidence is gathered from wild and domestic canids and from human and animal models where shared physiological or biological processes provide insight. Chewing appears to promote biological fitness, providing benefits such as dental and oral hygiene, digestive health, bone strength, psychological health, and stress management. Furthermore, this article discusses the evolutionary importance of chewing, the mechanisms underlying bite force, chew rate and morphology, and the development of chewing throughout a dog's life, from primary teeth eruption to senescence. Application of the Five Domains framework for animal welfare helps assess the impact of chewing, or lack thereof, on a dog's welfare. A dog's preference for chew items is primarily driven by odour, taste, and mouthfeel. Macronutrient proportions may also play a role in food preferences, which, in turn, can affect the selection of chewable items. A lack of preferred chew items may result in redirected chewing toward less appropriate items, such as non-food chews that could be harmful to dentition or the gastrointestinal tract (GIT). Chewing on such inappropriate items may also lead to the adoption of alternative oral behaviours or reduced their contentment by impeding telos. Overall, chewing positively impacts a dog's physical and psychological health, contributing to its welfare and appearing essential as a regular part of a dog's daily life. However, the significant benefits of chewing must be carefully weighed against potential risks.

The Nutritional Pathway Between Tooth Loss and Healthy Ageing: A Longitudinal Study of Older American Adults

OBJECTIVES

This study examines the mediating role of nutritional intake in the relationship between tooth loss and healthy ageing in older American adults.

METHODS

A secondary data analysis was conducted using the Health and Retirement Study (HRS), a longitudinal survey of American older adults aged 50 years and over. Data from six waves from 2006 to 2016 were used. Nutritional intake was assessed in 2013 using ten essential nutrients, categorised as adequate or inadequate based on national dietary recommendations. Healthy ageing was an aggregate variable composed of freedom from cognitive impairment, freedom from disability, and high physical functioning. Tooth loss was measured as a dichotomous variable (edentate/dentate). Structural equation modelling was used to assess the associations between tooth loss in 2012, nutrition in 2013, and healthy ageing in 2016, accounting for demographic/socioeconomic factors and behaviours.

RESULTS

A total of 3665 participants were included on the analysis. A significant association was found between being dentate in 2012 and nutritional intake in 2013 (coefficient 0.63: 95% CI: 0.62, 0.54, p < 0.001). Healthy ageing in 2016 was significantly influenced by socioeconomic factors in 2006 (coefficient 0.84: 95% CI: 1.38, 1.42, p < 0.001) and nutrition in 2013 (coefficient 0.05: 95% CI: 0.04, 0.05, p < 0.001). Non-Black individuals showed a significant association with healthy ageing.

CONCLUSIONS

The findings underscore the complex interplay of nutrition, socioeconomic status, health behaviours, and oral health in predicting healthy ageing trajectories. This study highlights the importance of oral health to maintaining adequate nutritional intake, which in turn promotes healthy ageing.

Mastication Influences Human Brain Anatomy

Objectives

The purpose of this observational clinical study was to evaluate the relationship between brain anatomical and volumetric changes in white matter, grey matter, and cerebral cortex thickness with the number of functional occlusal pairs present in the mouth.

Material and Methods

The number of functional occlusal pairs in 70 patients was counted and non-invasive brain analysis was performed using magnetic resonance imaging. The volume of grey matter, white matter, and thickness of the cortex in different areas of the brain were determined by SPM12 and CAT12 software. Multiple regression model corrected for multiple comparisons using FDR and Spearman correlation coefficient were calculated for statistical comparison.

Results

A total of 70 (39 male, 31 female) were analysed, with an average number of occlusal pairs of 10.21 (3.99). According to the Spearman correlation coefficient, a lower number of occlusal pairs was related to a reduction in white matter (right external capsule and posterior limb of the internal capsule), a reduction in grey matter (right temporal superior and medial gyrus and left cerebellum crus 1) and a reduction in thickness of the cerebral cortex (rostral anterior cingulated cortex of the right hemisphere and areas in the right and left hemisphere, especially in the frontal cortex).

Conclusions

The number of occlusal pairs is related to the volume of white matter, grey matter, and thickness of the cerebral cortex in areas of the brain that are directly involved in the onset and progression of Alzheimer's disease and other dementias.

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.

Factors associated with health-related quality of life on mental and oral health in patients with cancer and cancer survivors using the Korea National Health and Nutrition Examination Survey (2005-2018)

Objective

To investigate the association of mental and oral health with the health-related quality of life (HRQOL) in patients with cancer and cancer survivors.

Methods

This cross-sectional study involved 1643 patients with cancer and 1628 individuals who survived cancer (aged ≥ 19 years) using data from the 2005-2018 Korean National Health and Nutrition Examination Survey. The data were analyzed using SAS survey procedures (version 9.4), t-tests, χ2 test, and multiple regression.

Results

Regarding differences in mental and oral health factors by group, the results revealed significant differences between depression, suicidal ideation, subjective oral health, chewing problems, and speaking problems due to oral issues. The HRQOL of patients with cancer was lower than that of cancer survivors. The factors influencing HRQOL in both patients with cancer and cancer survivors were education status, economic activity, subjective health, suicidal ideation, and speaking problems due to oral issues. HRQOL was also associated with depression in patients with cancer.

Conclusions

Patients with cancer had a lower HRQOL than cancer survivors. The two groups of patients showed significant differences in the factors associated with HRQOL. Therefore, customized health programs and policies should be developed and implemented for each group to improve their QOL.

DO ORAL CARE AND REHABILITATION IMPROVE COGNITIVE FUNCTION? A SYSTEMATIC REVIEW OF CLINICAL STUDIES

OBJECTIVES

An increasing number of studies have identified an association between oral health status and cognitive function. However, the effect of oral interventions, including oral health care, dental treatment and oral motor exercises, on cognitive function remains unclear. This systematic review examined whether oral interventions contribute to the long-term improvement of cognitive status.

METHODS

Four databases were searched (MEDLINE, Web of Science, Cochrane Library, and ICHUSHI Web) to identify randomized and nonrandomized controlled trial studies and prospective cohort studies from inception until 1 September 2023, published in English or Japanese. The Cochrane risk of bias tool for randomized controlled trials and the risk of bias assessment tool for nonrandomized studies were used to assess bias risk.

RESULTS

A total of 20 articles were included in the qualitative analysis; 13 articles were published in English, and 7 were published in Japanese. The implemented interventions were oral care in 8 studies, dental treatment in 8 studies, and oral motor exercise in 4 studies. One study found a significant effect on attention following oral care intervention. Some dental treatments influenced cognitive function, although a clear positive effect was not determined. In 1 study, attention and working memory improved in the chewing exercise group.

CONCLUSIONS

Several studies verified the improvement effects of oral interventions, such as oral care, dental treatment, and oral motor exercise, on cognitive function or impairment. However, there was still a lack of conclusive evidence that such an intervention clearly improved cognitive function. To clarify the effects of oral interventions on cognitive function, it is necessary to examine participants, interventions, and outcome measures in detail.

Risk factors of cognitive impairment: Impact of decline in oral function

Cognitive impairment and subsequent dementia are the major causes of disability and need for nursing care among older people in worldwide. The purpose is to review well-known risk factors for cognitive impairment and dementia, focusing on the relationship between decline in oral function and current prevention strategies. Various non-modifiable and modifiable risk factors are related to cognitive impairment. Effects of oral function to cognitive impairment is not yet well recognized in the medical community, although masticatory function, occlusal force, and number of teeth have been reported to be related to cognitive function. Furthermore, occlusal force rather than number of teeth was significantly related to the early stages of cognitive impairment, and that a decline in occlusal force seemed to lead to cognitive impairment directly and indirectly through dietary intake. This relationship was significant only for occlusal force, which may be associated with the early stages of cognitive decline. Nutritional change caused by reduced masticatory function is suggested as a possible explanation. Therefore, rehabilitation or maintenance of oral function should be sought to prevent cognitive impairment.

Dynamic Correlations and Disorder in the Masticatory Musculature Network

BACKGROUND

Temporomandibular joint (TMJ) disorders, which affect millions of people worldwide, have multiple etiological factors that make an accurate diagnosis and effective treatments difficult. As a consequence, the gold standard diagnostic criteria for TMJ disorders remain elusive and often depend on subjective decisions.

AIM

In this context, the lack of a non-invasive quantitative methodology capable of assessing the functional physiological state and, consequently, identifying risk indicators for the early diagnosis of TMJ disorders must be tackled and resolved.

METHODOLOGY

In this work, we have studied the biomechanics and viscoelastic properties of the functional masticatory system by a non-invasive approach involving 52 healthy subjects, analysed by statistical-physics analysis applied to myotonic measurements on specific points of the masticatory system designing a TMJ network composed of 17 nodes and 20 links.

RESULTS

We find that the muscle tone and viscoelasticity of a specific cycle linking frontal, temporal, and mandibular nodes of the network play a prominent role in the physiological functionality of the system. At the same time, the functional state is characterised by a landscape of nearly degenerated levels of elasticity in all links of the network, making this parameter critically distributed and deviating from normal behaviour.

CONCLUSIONS

Time evolution and dynamic correlations between biomechanics and viscoelastic parameters measured on the different cycles of the network provide a quantitative framework associated with the functional state of the masticatory system. Our results are expected to contribute to enriching the taxonomy of this system, primarily based on clinical observations, patient symptoms, and expert consensus.

Association of Denture Use and Chewing Ability with Cognitive Function Analysed Using Panel Data from Korea Longitudinal Study of Aging (2006-2018)

This study aimed to investigate the association between denture use, chewing ability, and cognitive function in Korean middle-aged adults, using samples representing middle-aged people at the national level. This longitudinal study included 9998 middle-aged adults using the Korea Longitudinal Study of Aging 7th special survey data. Denture use, chewing ability, health-related factors, and general characteristics were assessed using the Computer-Assisted Personal Interview. After controlling for general characteristics using a generalized estimating equation model, the association of denture use and Mini-Mental State Examination (MMSE) scores with the chewing ability of those with or without dentures and MMSE scores were analysed. Among them, 24% of participants wore dentures, and 35.1% complained of difficulty chewing when wearing dentures. Among the participants who did not wear dentures, 16.4% complained of difficulty chewing. MMSE scores were lower among denture wearers than non-denture wearers (β = -0.026, p < 0.001). In both groups, MMSE scores decreased with chewing difficulty and were significantly reduced among non-denture wearers (p < 0.05). Chewing ability was closely associated with cognitive functioning. Therefore, in order to prevent cognitive decline, chewing discomfort while wearing dentures must be eliminated, and oral health must be maintained.

Association between oral health and cognitive function among Chinese older adults: the Taizhou imaging study

BACKGROUND

We aimed to investigate the association between oral health and cognitive function in a sample of older adults from a Chinese rural community.

METHODS

The cross-sectional cognitive function of 677 individuals were assessed by Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA). A comprehensive profile of the oral health status was evaluated by questionnaire and clinical examination.

RESULTS

Multiple covariates-adjusted regression models demonstrated decayed teeth (DT) and decayed/missing/filled teeth (DMFT) were negatively associated with MoCA score (all p < 0.05). Calculus index (CI) and clinical attachment loss (CAL) were significantly associated with the lower MoCA, short-term memory and executive function score, respectively (all p < 0.05). Additionally, participants with missing teeth unrestored tend to get lower MMSE and MoCA scores (p < 0.05). The results also showed that increased DT and CI were modestly associated with higher odds of cognitive impairment (p < 0.05).

CONCLUSIONS

There is an association between oral health and global cognition. Poor periodontal status was strongly associated with worse global cognition performance, especially in the short-term memory and executive domain for the aging population.

Poor Oral Health and Risk of Incident Dementia: A Prospective Cohort Study of 425,183 Participants

BACKGROUND

The association between poor oral health and the risk of incident dementia remains unclear.

OBJECTIVE

To investigate the associations of poor oral health with incident dementia, cognitive decline, and brain structure in a large population-based cohort study.

METHODS

A total of 425,183 participants free of dementia at baseline were included from the UK Biobank study. The associations between oral health problems (mouth ulcers, painful gums, bleeding gums, loose teeth, toothaches, and dentures) and incident dementia were examined using Cox proportional hazards models. Mixed linear models were used to investigate whether oral health problems were associated with prospective cognitive decline. We examined the associations between oral health problems and regional cortical surface area using linear regression models. We further explored the potential mediating effects underlying the relationships between oral health problems and dementia.

RESULTS

Painful gums (HR = 1.47, 95% CI [1.317-1.647], p <  0.001), toothaches (HR = 1.38, 95% CI [1.244-1.538], p <  0.001), and dentures (HR = 1.28, 95% CI [1.223-1.349], p <  0.001) were associated with increased risk of incident dementia. Dentures were associated with a faster decline in cognitive functions, including longer reaction time, worse numeric memory, and worse prospective memory. Participants with dentures had smaller surface areas of the inferior temporal cortex, inferior parietal cortex, and middle temporal cortex. Brain structural changes, smoking, alcohol drinking, and diabetes may mediate the associations between oral health problems and incident dementia.

CONCLUSION

Poor oral health is associated with a higher risk of incident dementia. Dentures may predict accelerated cognitive decline and are associated with regional cortical surface area changes. Improvement of oral health care could be beneficial for the prevention of dementia.

The Masticatory Activity Interference in Quantitative Estimation of CA1, CA3 and Dentate Gyrus Hippocampal Astrocytes of Aged Murine Models and under Environmental Stimulation

Studies indicating the influence of masticatory dysfunction, due to a soft diet or lack of molars, on impairing spatial memory and learning have led to research about neuronal connections between areas and cell populations possibly affected. In this sense, with scarce detailed data on the subfields of hippocampus in dementia neurodegeneration, there is no information about astrocytic responses in its different layers. Thus, considering this context, the present study evaluated the effects of deprivation and rehabilitation of masticatory activity, aging, and environmental enrichment on the stereological quantification of hippocampal astrocytes from layers CA1, CA3, and DG. For this purpose, we examined mature (6-month-old; 6M), and aged (18-month-old; 18M) mice, subjected to distinct masticatory regimens and environments. Three different regimens of masticatory activity were applied: continuous normal mastication with hard pellets (HD); normal mastication followed by deprived mastication with equal periods of pellets followed by soft powder (HD/SD); or rehabilitated masticatory activity with equal periods of HD, followed by powder, followed by pellets (HD/SD/HD). Under each specific regimen, half of the animals were raised in standard cages (impoverished environment (IE)) and the other half in enriched cages (enriched environment (EE)), mimicking sedentary or active lifestyles. Microscopic stereological, systematic, and random sampling approaches with an optical dissector of GFAP-immunolabeled astrocytes were done, allowing for an astrocyte numerical estimate. Stratum moleculare and hilus, from the dentate gyrus (DG) and Strata Lacunosum-Moleculare, Oriens, and Radiatum, similarly to the dentate gyrus, showed no significant change in any of the investigated variables (age, diet, or environment) in these layers. However, in Stratum radiatum, it was possible to observe significant differences associated with diet regimens and age. Therefore, diet-related differences were found when the HD 18M IE group was compared to the HD/SD/HD 18-month-old group in the same environment (IE) (p = 0.007). In the present study, we present modulatory factors (masticatory function, environmental enrichment, and aging) for the differentiated quantitative laminar response in the hippocampal regions, suggesting other studies to read the plasticity and responsiveness of astrocytes, including the molecular background.

Does the Loss of Teeth Have an Impact on Geriatric Patients’ Cognitive Status?

Significant changes in the microstructure of the brain cause dementia and other mental declines associated with aging and disease. Although research has established a connection between oral health and dementia, the underlying pathologic mechanisms are still unknown. Aim: Our aim was to evaluate dentures’ impact on the cognitive state of geriatric patients. Material and methods: A total of 108 individuals seeking treatment at the Faculty of Dental Medicine in Iasi, Romania, participated in the study, which ran from May 2022 to October 2022. Cognitive dysfunction was assessed using the Mini-Mental State Examination. The acquired data were analyzed with IBM SPSS 26.0, and the p-value was set at 0.05. Results: The average value of the MMSE score was 21.81 ± 3.872. Differences between groups of wearer/non-wearer subjects were statistically significant for most of the questions in the questionnaire. Linear regression analysis showed that individuals with a high MMSE score have prosthodontic treatment. A decrease in the MMSE score is associated with a decrease in masticatory efficiency (B = 1.513, p = 0.268). Conclusions: This study provides further evidence that tooth loss is associated with worse cognitive performance. It is thus conceivable that the necessary effects can be achieved by increasing the efforts dedicated to preventing tooth loss in the adult population.

The Relationships of Dentition, Use of Dental Prothesis and Oral Health Problems with Frailty, Disability and Diet Quality: Results from Population-Based Studies of Older Adults from the UK and USA

OBJECTIVES

This study examined the relationships of dental status, use and types of dental prothesis and oral health problems, individually and combined, with diet quality, frailty and disability in two population-based studies of older adults.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

Men form the British Regional Heart Study (BRHS) (aged 85±4 years in 2018; n=1013) and Men and Women from the Health, Aging, and Body Composition (HABC) Study (aged 75±3 years in 1998-99; n=1975).

MEASUREMENTS

Physical and dental examinations and questionnaires were collected with data available for dental status, oral problems related to eating, diet quality, Fried frailty phenotype, disability based on mobility limitations, and activities of daily living (ADL). The associations of dental status and oral health problems, individually and combined, with risk of frailty and disability were quantified. The relationship with diet quality was also assessed.

RESULTS

In the BRHS, but not HABC Study, impaired natural dentition without the use of dentures was associated with frailty independently. This relationship was only established in the same group in those with oral problems (OR=3.24; 95% CI: 1.30-8.03). In the HABC Study, functional dentition with oral health problems was associated with greater risk of frailty (OR=2.21; 95% CI: 1.18-4.15). In both studies those who wore a full or partial denture in one or more jaw who reported oral problems were more likely to have disability. There was no association with diet quality in these groups.

CONCLUSION

Older adults with impaired dentition even who use dentures who experience self-report oral problems related to eating may be at increased risk of frailty and disability. Further research is needed to establish whether improving oral problems could potentially reduce the occurrence of frailty and disability.

Malocclusion impairs cognitive behavior via AgRP signaling in adolescent mice

Introduction

Occlusal disharmony induced by deteriorating oral health conditions, such as tooth loss and decreased masticatory muscle due to sarcopenia, is one of the causes of cognitive impairment. Chewing is an essential oral function for maintaining cognitive function not only in the elderly but also in young people. Malocclusion is an occlusal disharmony that commonly occurs in children. The connection between a decline in cognitive function and malocclusion in children has been shown with chronic mouth breathing, obstructive sleep apnea syndrome, and thumb/digit sucking habits. However, the mechanism of malocclusion-induced cognitive decline is not fully understood. We recently reported an association between feeding-related neuropeptides and cognitive decline in adolescent mice with activity-based anorexia. The aim of the present study was to assess the effects of malocclusion on cognitive behavior and clarify the connection between cognitive decline and hypothalamic feeding-related neuropeptides in adolescent mice with malocclusion.

Methods

Four-week-old mice were randomly assigned to the sham-operated solid diet-fed (Sham/solid), sham-operated powder diet-fed (Sham/powder), or malocclusion-operated powder diet-fed (Malocclusion/powder) group. We applied composite resin to the mandibular anterior teeth to simulate malocclusion. We evaluated cognitive behavior using a novel object recognition (NOR) test, measured hypothalamic feeding-related neuropeptide mRNA expression levels, and enumerated c-Fos-positive cells in the hypothalamus 1 month after surgery. We also evaluated the effects of central antibody administration on cognitive behavior impairment in the NOR test.

Results

The NOR indices were lower and the agouti-related peptide (AgRP) mRNA levels and number of c-Fos-positive cells were higher in the malocclusion/powder group than in the other groups. The c-Fos-positive cells were also AgRP-positive. We observed that the central administration of anti-AgRP antibody significantly increased the NOR indices.

Discussion

The present study suggests that elevated cerebral AgRP signaling contributes to malocclusion-induced cognitive decline in adolescents, and the suppression of AgRP signaling can be a new therapeutic target against cognitive decline in occlusal disharmony.

Unhealthy oral status contributes to the older patients with cognitive frailty: an analysis based on a 5-year database

BACKGROUND

Oral health is associated with the onset and deterioration of cognitive function and physical frailty, which can be improved with appropriate interventions. However, far too little attention has been paid to oral health status of elderly with cognitive frailty. The objective of this study was to investigate the oral health status and potential risk factors of elderly hospitalized patients aged 60 years or older with cognitive frailty.

METHODS

The participants' assessment data derived from the Comprehensive Geriatric Assessment Database of hospitalized patients from The First Affiliated Hospital of Chongqing Medical University. Data were collected from April 2016 to December 2021. All participants underwent a face-to-face assessment conducted by professional evaluators. Physical frailty was defined by Fried's criteria. Cognitive function was assessed by Mini Mental State Examination (MMSE). The cognitive frailty is characterized by the simultaneous presence of at least 1 Fried's criteria and mild cognitive impairment according to Diagnostic and Statistical Manual of Mental Disorders 5th edition. The oral health was assessed according to 10-item Brief Oral Health Status Examination (BOHSE). The general demographic characteristics, BOHSE scores were compared between the cognitive frailty and non-cognitive frailty (control group). The score of BOHSE and ten items were included in the binary logistic regression analysis. The covariate characteristics were adjusted for a final model with a multivariate analysis.

RESULTS

A total of 425 patients (245 females) with cognitive frailty and 491 patients (283 females) with non-cognitive frailty were enrolled in this retrospective study. Univariate analysis showed statistically significant differences in age, education level, living arrangement, diabetes, Body Mass Index (BMI), Pittsburgh Sleep Quality Index (PSQI), depression between the two groups. The total BOHSE score of cognitive frailty was higher than that of the control group (4.35 ± 2.68 vs. 3.64 ± 2.60, Z = 4.07, P < 0.001). The average scores and the proportions of health changes and unhealthy states of tongue, mucosa tissue, gums, natural teeth, dentures, masticatory teeth and oral hygiene in cognitive frailty were greater than those of the control group (all P < 0.05). The binary logistical regression analysis showed that four or more natural teeth decayed or broken was independently associated with cognitive frailty after adjusting the age, gender, education level, living arrangement and BMI, PSQI, diabetes and depression (OR = 1.91, 95%CI: 1.20-3.07, P = 0.007). Additionally, while in the chewing position, those cases with a normal-occlusal-relationship number of less than 11 pairs had a higher risk of cognitive frailty than those with 12 pairs or more.

CONCLUSIONS

The oral health status of older hospitalized patients over 60 years with cognitive frailty was worse than that of patients with non-cognitive frailty. But only four or more natural teeth decayed or broken and a reduction in chewing pairs were independent risk factors for cognitive frailty.

Molar loss further exacerbates 2-VO-induced cognitive impairment associated with the activation of p38MAPK/NFκB pathway

BACKGROUND

Vascular dementia is characterized by reduced cognitive function due to chronic cerebral hypoperfusion and has become a significant public health challenge as the global population ages. Recent studies suggested that molar loss, a common problem among the elderly, may trigger the development of cognitive decline. Our previous study found that the molar loss affected cognitive dysfunction, and the astrocytes in the hippocampus of chronic cerebral ischemia rats were affected, but the underlying mechanism is unclear.

METHODS

In this study, we established the animal model of molar loss with 2-VO rats and the Morris water maze was used to test the cognitive ability of rats in each group. The damage to neurons was observed via Nissl staining, and neuronal apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in the hippocampus of the rats. Quantitative Real-Time PCR and immunohistochemistry and histology (IHC) were used to detect the expression of p38MAPK, NFκB, caspase 3, and iNOS in the hippocampus. The astrocytes were detected by IHC and Immunofluorescence analysis for GFAP. After 2-VO MO surgery, rats were administered DMSO or p38MAPK inhibitor (SB203580) by intrathecal injection.

RESULTS

The Morris water maze test showed that the molar loss aggravated spatial memory learning ability with chronic cerebral ischemia decreased in the rats. The neuronal damage and more apoptotic cells were observed in the hippocampus of 2-VO rats. After the molar loss, the mRNA and protein expression of iNOS, p38MAPK, NFκB, and caspase 3 were further upregulated in 2-VO rats. Molar loss upregulated GFAP expression, and the p38MAPK-positive cells were labeled with the astrocyte marker GFAP. SB203580 reduced cognitive impairment and apoptosis of hippocampal neurons in 2-VO rats following the molar loss.

CONCLUSION

Molar loss can aggravate cognitive impairment in 2-VO rats to a certain extent. The mechanism of molar loss exacerbating the cognitive decline in 2-VO rats may be associated with the activation of the p38MAPK-NFκB-caspase 3 signaling pathway, which induces neuronal apoptosis.

The Sedentary Lifestyle and Masticatory Dysfunction: Time to Review the Contribution to Age-Associated Cognitive Decline and Astrocyte Morphotypes in the Dentate Gyrus

As aging and cognitive decline progresses, the impact of a sedentary lifestyle on the appearance of environment-dependent cellular morphologies in the brain becomes more apparent. Sedentary living is also associated with poor oral health, which is known to correlate with the rate of cognitive decline. Here, we will review the evidence for the interplay between mastication and environmental enrichment and assess the impact of each on the structure of the brain. In previous studies, we explored the relationship between behavior and the morphological features of dentate gyrus glial fibrillary acidic protein (GFAP)-positive astrocytes during aging in contrasting environments and in the context of induced masticatory dysfunction. Hierarchical cluster and discriminant analysis of GFAP-positive astrocytes from the dentate gyrus molecular layer revealed that the proportion of AST1 (astrocyte arbors with greater complexity phenotype) and AST2 (lower complexity) are differentially affected by environment, aging and masticatory dysfunction, but the relationship is not straightforward. Here we re-evaluated our previous reconstructions by comparing dorsal and ventral astrocyte morphologies in the dentate gyrus, and we found that morphological complexity was the variable that contributed most to cluster formation across the experimental groups. In general, reducing masticatory activity increases astrocyte morphological complexity, and the effect is most marked in the ventral dentate gyrus, whereas the effect of environment was more marked in the dorsal dentate gyrus. All morphotypes retained their basic structural organization in intact tissue, suggesting that they are subtypes with a non-proliferative astrocyte profile. In summary, the increased complexity of astrocytes in situations where neuronal loss and behavioral deficits are present is counterintuitive, but highlights the need to better understand the role of the astrocyte in these conditions.

The impact of tooth loss on cognitive function

Objective

To investigate if there is epidemiological evidence of an association between edentulism and cognitive decline beside that currently available from limited sample-sized case series and cross-sectional studies considering limited co-variables.

Materials and methods

Data from two USA national health surveys [NHIS 2014–2017 and NHANES 2005–2018] were analyzed using multinomial logistic regression to study the impact of type of edentulism and number of remaining teeth on memory and concentration problems. Age, gender, socioeconomic status, education level, cardiovascular health index, body mass index, exercise, alcohol, smoking habits, and anxiety and depression were used as covariates.

Results

The combined population sample was 102,291 individuals. Age, socioeconomic status, educational level, anxiety and depression levels, and edentulism showed the highest odds ratios for cognitive decline. Number of teeth present in the mouth was found to be a predictor of cognitive status. This association showed a gradient effect, so that the lower the number of teeth, the greater the risk of exhibiting cognitive decline.

Conclusions

Edentulism was found among the higher ORs for cognitive impairment.

Clinical relevance

Maintenance of functional teeth through the promotion of oral health may contribute to the preservation of memory/concentration and other essential cognitive functions. Thus, increasing and efficiently coordinating efforts aimed at preventing of tooth loss in the adult population could substantially contribute to reduce the incidence of cognitive impairment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04318-4.