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Abstract

Objective

To systematically review studies on oral frailty and its associations.

Background

Oral frailty is prevalent and yet under-recognised in the elderly. It has been linked to adverse outcomes including increased mortality, frailty and dementia.

Methods

The databases were searched for published literature up to January 2024 using a prespecified search strategy. The following terms were used: ’oral’ AND ‘frailty’ The search was restricted to English publications. Two independent reviewers screened the retrieved references through the titles and abstracts to test them against the eligibility criteria for inclusion. The full texts of qualified publications were read and selected for the final decision after discussion between the two reviewers.

Results

15 studies were identified with 12 cross-sectional studies and three prospective cohort studies. The definitions of oral frailty varied and outcomes were grouped into categories namely physical frailty, social frailty, cognition, mood, nutrition, quality of life and biochemical indices. Oral frailty results in negative outcomes such as increased physical frailty, social frailty, late life depression and deteriorating nutritional status. It could predict declining cognition and decreased health-related quality of life.

Conclusion

This review identified associations between oral frailty and geriatric syndromes and revealed poorer outcomes in elderly with oral frailty. Early identification of oral frailty can be used to predict negative outcomes. Addressing oral frailty involves a multidisciplinary approach, combining dental care, nutrition and overall health to improve the quality of life. It is hoped that we can investigate and tailor interventions, allowing our elderly to age well and live well.

Keywords

oral frailty outcomes review elderly

Introduction

Oral frailty is an ever growing problem yet under-recognised in the elderly population.¹ It has been linked to various adverse health outcomes in terms of frailty, pneumonia, dementia and mortality.² In a recent meta-analysis, the prevalence of oral frailty in older adults was 28% (95% CI 20–36%).¹ Of note, there was a higher prevalence of oral frailty in China of 40% (95% CI 32–47%) compared to Japan of 22% (95% CI 11–33%).¹ By improving oral function, it could potentially improve the health status of the older person in terms of nutrition, cognition and function. This in turn impacts the quality of life (QoL) of the older person.^3,4

The oral cavity is made up of various parts including the lips, tongue, palate and teeth. Together, they perform complex and diverse functions which include the consumption of food, maintaining tongue pressure, chewing and swallowing, It is also vital for articulation and good communication.⁵ All of the above functions decline with age.⁶ At the same time, eating behaviours consist of other aspects eg psychosocial, enjoyment and are closely linked with the QoL of the older adult.^4,7

There have been varying definitions of oral frailty over the years. Tanaka et al. describe the multifaceted decline of oral function in the elderly⁸ and selected six oral health measures (i.e., number of teeth, masticatory function, difficulty chewing, oral diadochokinesis, tongue pressure, and difficulty swallowing). Oral frailty was present if there was poor status in three or more of these six oral health items.⁹ According to the Japan Dental Association, oral frailty involves vulnerability in oral health status due to age-related changes (number of teeth, oral hygiene, oral functions, etc.) coupled with a reduced interest in oral health and physical and mental reserve capacity with deterioration of eating function.¹⁰ Minakuchi et al. created the Oral Frailty 5-Item Checklist (OF-5) as a simple tool for this objective which includes five criteria for oral frailty: (i) fewer teeth, (ii) difficulty in chewing, (iii) difficulty in swallowing, (iv) dry mouth, and (v) low articulatory oral motor skills.¹¹

Various risk factors have been found to influence oral frailty. Hu et al. described these factors including age, gender, education level, frailty score, frailty stage, number of dentures, dry mouth, subjective chewing difficulty, oral health score and sleep quality.¹² At the same time, oral frailty itself is a risk factor for geriatric syndromes. When an older adult develops problems with chewing or swallowing, they tend to avoid certain types of food and this dietary restriction causes a vicious cycle, leading to malnutrition and further weakness in chewing ability. This in turn contributes to the onset of sarcopaenia and physical frailty conferring poorer functional outcomes resulting in a greater need for long term care and increased mortality.^2,13

This review aims to delineate the associations between oral frailty and outcomes that are relevant to the geriatric population namely physical and social frailty, cognition, mood, nutrition, quality of life and mortality. In doing the above and achieving better understanding of the association, it can propel the need for healthcare professionals and policymakers alike to institute earlier detection for oral frailty and undertake research to identify relevant outcome measures.

Methods

Pubmed and Web of Science databases were searched for published literature up to January 2024 using a prespecified search strategy. Search terms included controlled terms and free text terms. The following terms were used (including synonyms and closely related words) as index terms or free text words: ’oral’ AND ‘frailty’ The search was restricted to English publications with date restriction up till January 2024. Duplicate articles were excluded.

Participants were elderly aged 65 years and above. Various recruitment settings were included (nursing homes, hospitals, community‐dwelling). The study designs included observational, longitudinal and prospective studies. The focus was on studies which addressed oral frailty directly and the outcomes. Outcomes included the following: physical frailty (gait performance, locomotive syndrome), social frailty, mortality and quality of life. Studies that were meta-analyses or systematic reviews were excluded in the final selection.

Two independent reviewers (WT and KS) checked the retrieved references through the titles and abstracts of every publication against the eligibility requirements for inclusion in the review. The full texts of relevant publications were read and chosen for the final decision of inclusion after discussion between the two reviewers. All retrieved references were summarised into an excel file listing year of publication, first author name, title, journal. Other details included the study design, population, country, mean age (if available), definition of oral frailty, outcomes and association. The two reviewers discussed and aimed to resolve any disagreement that arose. In case of persistent dispute, a third reviewer (AY) was consulted to examine the abstracts where inconsistencies existed. The three reviewers would then discuss the outcome, whereby the final decision would be determined by the majority. The review protocol has been registered in OSF. ID osf.io/7gfs3.

Results

Selection of sources of evidence

The search found a total of 2599 results. Using the search terms “oral” and “frailty”, 1148 records were generated from Pubmed while 1451 articles were generated from Web of Science under their advanced search. The preliminary screening excluded 2568 articles that were not relevant.

The remaining 31 articles that were clearly relevant were eligible for full text review. The full texts of relevant publications were read and chosen for the final decision of meeting the inclusion criteria after discussion between the two reviewers.

Of these publications, 16 articles lacked a definition of oral frailty, did not include outcomes or were systematic reviews/meta-analyses. In total, 15 articles were included in the final selection for extraction and analysis of data Figure 1.

Figure 1.

Search strategy and selection of literature on oral frailty and its outcomes.

Characteristics of sources of evidence and results of individual studies

A total of 11 studies were conducted in Japan, two in Taiwan and two in Finland. The studies included 12 cross sectional studies and three prospective cohort studies. There were varying definitions of oral frailty and they looked at various outcomes. Table 1 highlights the characteristics of the studies demonstrating the association between oral frailty and outcomes.

Table 1.

showing characteristics of studies illustrating association between oral frailty and outcomes.

Study	Study design	Country, Population, Age	Definition of oral frailty (OF)	Outcomes	Results
Ya Wen Kuo et al Association between Oral Frailty and Physical Frailty among Rural Middle-Old Community-Dwelling People with Cognitive Decline in Taiwan: A Cross-Sectional Study	Cross Sectional	Taiwan Community dwelling elderl Mean age 79.7 years	Oral frailty checklist by the Japanese Dental Association <1>	Cognitive Impairment: Clinical Dementia Rating (CDR) The Study of Osteoporotic Fracture Index used for physical frailty (PF) <2>	80.6% of the elderly with a high risk of OF were in the pre-frailty and frailty stages. PF was significantly associated with the OF subdomains of difficulty eating hard food (Odds Ratio OR = 2.17, 95% Confidence Interval CI = 1.21–3.88; p = 0.009), choking (OR = 2.64, 95% CI = 1.29–5.43; p = 0.008), denture use (OR = 2.44, 95% CI = 1.26–4.17; p = 0.008), inability to chew hard food (OR = 2.27, 95% CI = 1.48–5.0; p = 0.001), and high risk of OF (OR = 3.03, 95% CI = 1.51–6.1; p = 0.002) A linear correlation of OF mean score and PF was found. Elderly with high risk of OF had an OR of 3.03 for PF
Komatsu et al Association between Physical Frailty Subdomains and Oral Frailty in Community Dwelling Older Adults	Cross Sectional	Japan Community dwelling elderly Mean age 72.8 ± 5.6 years	Oral frailty- functional limitations in ≥3 of 6 domains <4>	Physical frailty with reference to the Japanese version of the Cardiovascular Health Study (J-CHS) <5>	PF risk (OR = 2.40, 95% CI: 1.22–4.75, p = 0.012) was associated with OF in multivariate analysis. In secondary analysis, among PF subdomains, gait speed (OR = 0.85, 95% CI: 0.73–0.97, p = 0.019) was associated with OF
Iwasaki et al Oral frailty and gait performance in community dwelling older adults: findings from the Takashimadaira study	Cross Sectional	Japan Community dwelling elderly Mean age 77.1 ± 4.7 years	Oral frailty definition as per Tanaka et al Number of teeth and denture use, masticatory performance, tongue pressure, oral diadochokinesis, self perceived oral function via Kihon Checklist <6>	Gait parameters assessed using modular platform systems : P-WALK (BTS Bioengineering Corp Milano Italy) measuring gait variables in dynamic phases <7>	After adjusting for confounders, the participants with OF had slower gait speed, shorter stride and step length, wider step width, and longer double support duration. A positive linear relationship was observed between the number of OF components and the variability of stride length and step length. OF was associated with poor gait performance. The accumulation of oral health deficits had a dose response relationship with the decline in gait performance.
Tanaka et al Oral Frailty as a Risk Factor for Physical Frailty and Mortality in Community Dwelling Elderly	Prospective cohort study	Japan Community dwelling elderly Mean age 73.0 ± 5.5 years	Oral frailty defined as ≥3 of 6 Domains <4> Oral examinations consisted of 16 measures namely 5 dental status, 8 oral functions, and 3 subjective difficulties <8> but chose 6 measures as the OF definition	Physical frailty - Cardiovascular Health Study index criteria Disability and mortality data were obtained from the long term care insurance (LTCI) system. <9>	OF was significantly associated with 2.4-, 2.2-, 2.3-, and 2.2-fold increased risk of PF, sarcopenia, disability, and mortality respectively Over the 45-month follow-up period, 3.2 % died. There was a significant difference in the incidence of mortality between the orally frail and prefrail (Hazards Ratio HR 1.99; 95% CI 1.14−3.57 p < .022). Baseline OF status significantly predicted susceptibility to PF, sarcopenia, need for LTCI, and mortality
Hiltuen et al Relationship between Fried’s frailty phenotype and oral frailty in long-term care residents	Cross sectional	Helsinki, Finland Long term care residents Mean age 82 years	Oral Frailty <10> (i) salivation as normal or dry mouth (ii) presence of food residues (iii) inability to keep mouth open during the examination (iv) unclear speech (v) pureed or soft food diet (vi) painfulness	Physical Frailty: Fried’s phenotypic criteria <11>	After adjustment for age and sex, a significant linear relationship remained between the number of OF signs and Fried’s frailty phenotype (P for linearity <0.001) There was a similar linear relationship between the accumulation of signs and frailty phenotype (P for linearity 0.006). Participants with more signs of OF had more often dementia, malnutrition, lower body mass index (BMI) and swallowing and chewing difficulties, and they needed more often help with eating and managing oral hygiene.
Puranen et al Relationship between oral frailty, health‑related quality of life and survival among long‑term care residents	Cross sectional	Helsinki, Finland Long term care residents Mean age 82 years	Oral Frailty <10> Defined by 6 signs	Health related Quality of life(HRQoL) using 15D quality of life instrument <12> 3-year mortality data was taken from central registers in March 2021.	HRQoL according to 15D decreased linearly as the severity of OF increased (p < 0.001). Eight dimensions of 15D (mobility, eating, speech, excretion, usual activities, mental function, vitality, and sexual activity) and total 15D score correlated negatively with the number of OF signs. 64% (n=224) died during the 3-year follow-up period.
Hironaka et al Association between oral, social, and physical frailty in community-dwelling older adults	Cross Sectional	Japan Community dwelling elderly Mean age 73.3 ± 6.6 years	Oral frailty as per Tanaka et al <4>	Physical frailty was assessed via the 5 categories <13> Social Frailty(SF) as per Makizako et al (2015) <14>	Participants with OF were older, were less independent in IADL, had lower physical and cognitive function, and tended to be depressed The results of the present study suggest that SF directly relates to OF and that both, OF and SF are directly related to PF.
Miyuki Nagatani et al Oral frailty as a risk factor for mild cognitive impairment in community dwelling older adults: Kashiwa study	longitudinal cohort study prospective cohort study	Japan Community dwelling elderly Mean 72.4 ± 5.2 years	Oral frailty as per Tanaka et al <4>	MIld cognitive impairment (MCI) defined as MMSE below 27 (Kaufer et al., 2008) <15>	The OF group had a significantly higher HR for new-onset MCI, after adjusting for confounders. A decrease in the number of remaining teeth, low tongue pressure, and difficulty eating tough foods significantly correlated with new-onset MCI. Co-existing OF and PF was associated with an increased risk of MCI.
Ying-Chun Lin et al Physical Frailty and Oral Frailty Associated with Late-Life Depression in Community Dwelling Older Adults	Cross sectional	Taiwan Community dwelling elderly Adults ≥65 years old 58% for 65-74 group, 42% for ≥75 years	Oral condition <16> Involved 6 components, namely dysphagia, xerostomia, masticatory performance, EI (indicating occlusal support), oral diadochokinetic rate and the Silness–Löe Plaque Index (representing oral hygiene)	Depression measured via GDS-15 <17> Physical frailty via the SOF index <2>	Factors associated with late-life depression were pre-physical frailty (adjusted odds ratio aOR = 3.61, 95% CI: 1.94–6.71), physical frailty (aOR = 53.74, 95% CI: 12.87–224.42), pre-oral frailty (aOR = 2.56, 95% CI: 1.12–5.84), and oral frailty (aOR = 4.89, 95% CI: 2.02–11.80). PF and OF were associated with late-life depression in a dose–response manner. PF, sarcopenia, insomnia, OF, dysphagia, and xerostomia exerted significant combined effects on late-life depression
Masanori Iwasaki et al A Two-Year Longitudinal Study of the Association between Oral Frailty and Deteriorating Nutritional Status among Community Dwelling Older Adults	Longitu- dinal	Japan Community dwelling elderly Mean age, 76.4 ± 4.1 years	Oral frailty as per Tanaka et al <4>	Nutrition: Mini Nutritional Assessment®- Short Form (MNA®-SF) <18> Deteriorating nutritional status: at risk of malnutrition or malnourished at the 2 year follow-up	OF was associated significantly with deteriorating nutritional status (OR 2.57; 95% CI 1.32–4.99). OF remained statistically significant after adding MNA®-SF score, poor appetite, JST-IC score, and depressive symptoms as covariates. There is also a significant association between the number of OF components and deteriorating nutritional status.
D. Hoshino et al Association between Oral Frailty and Dietary Variety among Community-Dwelling Older Persons: A Cross-Sectional Study	Cross sectional	Japan Community dwelling elderly ≥65 years Mean age 75.9 ± 6.3 years	Oral frailty as per Tanaka et al <4>	Dietary variety: via dietary variety score (DVS) <19>	The severity of OF was significantly associated with DVS after adjusting for potential confounders age, sex, BMI, habits of drinking and smoking, living arrangement, years of education, functional status, cognitive status, depressive symptoms, and medical history The higher the DVS, the lower the number of participants with <20 teeth and subjective difficulty in swallowing. The DVS and chewing ability were directly proportional.
M. Iwasaki et al Association between Oral Frailty and Nutritional Status among Community Dwelling Older Adults: the Takashimadaira Study	Cross sectional	Japan Community dwelling elderly Mean age: 77.0 ± 4.8 years	Oral frailty as per Tanaka et al <4>	Nutrition assessed via Mini Nutritional Assessment®- Short Form (MNA®-SF) <18> and also serum albumin Stratified into 3 groups using serum albumin levels: ≤3.8, 3.9, and ≥4.0 g/dL	After adjusting for potential confounders, the participants with OF had higher odds of more severe malnutrition using MNA®-SF (aOR: 2.17; 95% CI 1.58–2.98) and serum albumin level (aOR: 1.59; 95% CI: 1.10–2.31). The odds of more severe malnutrition based on the MNA®-SF score increased by 36% for each increase in the number of OF components. The magnitude of the effect of the number of components of OF on malnutrition based on serum albumin was near the limit of significance (p = 0.049).
Yuki Ohara et al Association of eating alone with oral frailty among community dwelling older adults in Japan	Cross- sectional study	Japan Community dwelling elderly Mean age 79.1 ± 4.5 years	Oral frailty as per Tanaka et al <4>	Dietary habits were assessed in terms of dietary quality via DVS <19> and eating behaviour measured by eating alone. <20>	Participants in the OF and preOF groups tend to be of significantly older age, lower food variety, higher percentage of eating alone, and higher scores on the GDS-15 (p < .05). Eating alone remained significantly associated with a higher OR of the presence and severity of OF even after adjusting for confounders e.g. age, sex, living status, employment, medical history, and depression
Yoshiaki Nomura et al Nutritional Status and Oral Frailty: A Community Based Study	Cross sectional	Japan Community dwelling elderly Mean age 71.5 ± 8.9 years	Oral Frailty checklist proposed by the Japan dental association <1>	Nutritional status - brief-type self-administered diet history questionnaire (BDHQ) <21> Number of remaining teeth Body Mass Index	The items concerning self-assessed oral function and daily activity showed almost no significant correlation with nutrition intakes. In addition, the number of remaining teeth had almost no significant correlation with nutrition intakes. In contrast, brushing teeth twice a day and regular attendance of dental clinic had significant correlation with intakes of most of the nutrients. Nutrients intake status was correlated with oral health behaviour but not oral function and number of remaining teeth.
Kusunoki et al Association between oral frailty and cystatin C-related indices—A questionnaire (OFI-8) study in general internal medicine practice	Cross- sectional	Japan Community dwelling elderly Mean age of 77.7±6.6 years	Oral Frailty Index-8 (OFI-8) <22>	Blood tests: Cr and CysC Height and weight Grip strength	Cr/CysC, eGFRcys/ eGFRcre and grip strength were significantly lower in both men and women in the high-risk group for OF (OFI-8 score >or equal to 4). A low cystatin C-related index is associated with a high risk of sarcopenia and OF whereas a high OFI-8 score recommends a precise evaluation of oral functions.

Association between oral frailty and physical frailty

Frailty is a syndrome of increased vulnerability to stressors and resultant homeostenosis that has increased prevalence with ageing and results in adverse health outcomes.^14,15 There are various models and operational criteria to determine physical frailty in an individual, ranging from Fried’s physical phenotype¹⁶ to Rockwood’s deficit accumulation model.¹⁷ A study looked at the prevalence of frailty in community dwelling older adults in Asia and found that the average prevalence was 20.5%.¹⁸

From our review, six studies were conducted on community-dwelling elderly in East Asia (Japan, Taiwan). A cross-sectional study from Taiwan evaluating elderly with cognitive decline found that physical frailty was significantly associated with the following oral frailty subdomains. There was an increased difficulty in eating hard food (Odds Ratio OR = 2.17, 95% CI = 1.21–3.88; p = .009), increased choking (OR = 2.64, 95% CI = 1.29–5.43; p = .008), denture use (OR = 2.44, 95% CI = 1.26–4.17; p = .008) and greater problems of chewing hard food (OR = 2.27, 95% CI = 1.48–5.0; p = .001). Challenges in eating was related to slowing of gait speed and physical frailty. Choking demonstrates swallowing impairment which affects nutritional status and also predicts physical frailty. Participants with physical frailty also demonstrated higher risk of oral frailty with odds ratio of 3.03 (OR = 3.03 , 95% CI 1.51–6.1, p = .002).¹⁹ To determine which subdomain of frailty is linked to oral frailty, Komatsu et al. examined elderly in the community with physical frailty parameters established as per the Japanese version of Cardiovascular Health study which included gait speed, weakness, exhaustion, low physical activity and weight loss. Secondary analysis demonstrated that a reduction in gait speed was associated with oral frailty (OR = 0.85, 95% CI: 0.73–0.97, p = .019).²⁰ Similarly, the Takashimadaira study demonstrated that individuals with oral frailty had poorer gait performance with reduced gait speed, decreased stride and step length, and increased step width with longer double support duration.²¹ Tanaka et al. demonstrated in their prospective cohort study that oral frailty has far-reaching detrimental effects apart from physical frailty alone with a 2.3 times higher risk of disability (HR = 2.35, 95% CI: 1.18–4.67, p = .015) and 2.1 times increased mortality risk (HR = 2.09, 95% CI:1.00–4.35, p = .048).⁸

Oral frailty and its inter-relationship with physical frailty not only poses a concern for community-dwelling individuals but also for institutionalised elderly.²² From our review, one study focused on nursing home residents. The FINnish ORAL Health Study demonstrated that oral frailty had a significant linear relationship with physical frailty as per the Fried frailty phenotype with p for linearity <0.001 after controlling for gender and age. Worsening oral frailty had downstream effects of higher prevalence of dementia and malnutrition which can result in increased care needs for the residents.²³

Association between oral frailty and social frailty

There is a lack of consensus on how to define social frailty. Bunt et al. in 2017 defined social frailty as a progressive state of being vulnerable to the loss or deprivation of resources that are necessary to fulfill one’s basic social needs throughout life²⁴ In a recent publication in 2013, Yamada et al. reported the social frailty index focusing on four factors: the degree of neighbourhood interaction, living alone, social participation, and economic status. Social frailty is present when two or more of the four items are applicable.²⁵ Individuals with social frailty are shown to have a greater risk of impairment associated with adverse social circumstances such as social isolation and lower frequency of going out.²⁶

From our review, Hironaka et al. aimed to establish the complex relationships between oral, social and physical frailty in community-dwelling elderly, highlighting that social frailty was closely linked to oral frailty.²⁷ OF was found in older adults with a lower level of education, reduced nutrition, worse physical and mental reserves, poor mood and polypharmacy.^8,27 As social function drops with a lowering of health knowledge, the consequences of suboptimal dental care, loss of teeth and a deterioration in oral function can occur. At the same time, there are fewer chances for conversation, which can lead to reduced tongue pressure, poorer masticatory ability and slowing tongue movement. This drop in oral and social function is closely connected to the waning general health status.²⁷

Association between oral frailty and cognition

Research has delved into the links between unhealthy oral status and cognitive impairment. Dibello et al. found a bidirectional relationship between Alzheimer’s Disease (AD) as well as late life cognitive disorders and oral frailty components.²⁸ Purported mechanisms included presence of pathological oral bacteria resulting in tooth loss which is associated with AD risk as well as the microbiota-gut-brain axis. Tooth loss could lead to a decrease in chewing ability resulting in decreased cerebral blood flow and cerebral neural activity that can lead to cognitive impairment. Both tooth loss due to gum disease and suboptimal tooth brushing were associated with a doubling of AD risk²⁹ and increased dementia risk.³⁰

P. gingivalis (a pathogen of gum disease) secretes a lipopolysaccharide that causes chronic inflammation which could potentially induce the onset and course of Alzheimer’s disease.³¹

From our review, one study in Japan investigated the impact of oral frailty on mild cognitive impairment. Nagatani et al. conducted a longitudinal prospective cohort study which found that oral frailty predicted a higher risk of new-onset MCI in community-dwelling older adults (HR 1.54 95% CI 1.05–2.24 p-value 0.026). New-onset MCI was correlated with reduced number of teeth, low tongue pressure, and difficulty consuming tough foods. In addition, there was an increased risk if both oral frailty and physical frailty were present.⁸

Association between oral frailty and mood

Strong links have been found between oral frailty and depression. How depressive symptoms are associated with it may involve a reduction in daily activities (e.g. lesser tooth brushing and fewer dental visits).³² The oral status (missing teeth, cavities and xerostomia) can also impact the severity of depression in the elderly.³³

From our review, oral frailty is associated with late-life depression in a Taiwanese study. Oral frailty had an increased odds ratio of 4.89 (aOR = 4.89, 95% CI: 2.02–11.80) with late-life depression in a dose-response relationship. When paired with xerostomia, oral frailty exerted a substantial impact on late-life depression. Medication-induced xerostomia was found to be higher in patients with polypharmacy and taking antidepressants.³⁴

Association between oral frailty and nutrition

Nutrition is a central element in frailty that requires both energy and protein as major players. Intuitively, oral frailty and unhealthy oral status will lead to restricted dietary intake leading to malnutrition which has an impact on the health of the elderly. The reduction in tongue pressure makes it challenging to form food boluses which in turn affects swallowing leading to decreased overall food consumption.⁵ A major factor is the masticatory function that influences how dietary status and oral health are related. Other factors asserting their impact include culture, life and personal preference.¹²

From our review, 3 Japanese studies looked at the links between oral frailty and nutrition. Iwasaki et al. illustrated the above in two papers. In a longitudinal study performed on community-dwelling older adults, a significant association between oral frailty and worsening nutritional status existed (adjusted odds ratio, 2.24; 95% confidence interval, 1.08–4.63) even after controlling for confounders.³⁵ A cross-sectional study found that the elderly with oral frailty had greater odds of being severely malnourished when assessed using Mini Nutritional Assessment Short Form ( MNA®-SF) (adjusted odds ratio: 2.17; 95% Cl: 1.58–2.98) and serum albumin (adjusted odds ratio: 1.59; 95% CI: 1.10–2.31).³⁶ Nomura et al. studied the effects of oral frailty on nutritional intake at a community level and found an association between oral health behaviour and nutrient intake. This was not present for oral function and the number of remaining teeth.¹²

Studies have also examined the influence of oral frailty on dietary habits and dietary variety. Hoshino et al. showed that the severity of OF was significantly associated with the dietary variety score (DVS). Dietary variety was assessed using DVS, a self-administered questionnaire for weekly food consumption. The rate of OF was 21.6%. After adjusting for potential confounders, Hoshino et al. found that the severity of OF was significantly correlated with DVS (Pre-OF; adjusted odds ratio [OR] = 1.687, 95% confidence interval [CI] = 1.219-2.335, OF; adjusted OR = 2.857, 95% CI = 1.489-5.484).³⁷ Interestingly, Ohara et al. did not find a significant association with dietary variety.³⁸ Instead, eating alone was significantly associated with oral frailty after adjusting for socioeconomic characteristics like work status and living circumstances.³⁸ This highlights the links between oral health, psychosocial factors and overall nutrition. Eating is not just a process of consuming food but it provides chances for socialising and engagement. At the same time, eating alone is linked to inactivity of the mouth whereby there is a reduction of oral function from fewer chewing motions and the absence of dialogue compared to eating together.³⁸

Association between oral frailty and QoL

Oral frailty is linked to various diseases and QoL.^4,6 A review done in 2021 found a positive association between denture wearing, tooth-related pain, gum diseases and poor Oral Health-Related QoL among the elderly.³⁹

From our review, the subset study conducted by Puranen et al. revealed that the health-related QoL declined linearly with the rise in the number of oral frailty signs.⁴⁰ Long term care residents who were in the lower oral frailty category were also noted to have better survival prediction.⁴⁰

Association between oral frailty and biochemical indices

Despite the presence of multiple screening instruments for oral frailty, there is yet to be an established biochemical marker to enable its early detection. Cystatin C has been established in studies to indicate renal function, unaffected by muscle mass and sarcopenia.⁴¹ Other biochemical reflectors of muscles mass include the ratio of creatinine to cystatin C(Cr/CysC) and the ratio of estimated glomerular filtration rate by cystatin C (eGFRcys) to creatinine eGFRcre (eGFRcys/eGFRcre).^42–44

From our review, Kusunoki et al. aimed to examine the relationship between cystatin C-related indices (Cr/CysC and eGFRcys/eGFRcre) and oral frailty. They illustrated significantly lower cystatin C-related indices in the high-risk group for oral frailty based on the OFI-8 across both genders. However, limitations of the study include lack of causality determination due to its cross-sectional nature.⁴⁵

Discussion

Oral frailty is one aspect of geriatric care that is gaining more attention in recent years.^1,3 It is associated with several geriatric syndromes such as physical frailty, social frailty, impaired cognition and low mood.² Early identification of oral frailty becomes crucial so as to intervene early before it has nutritional impacts and downstream deleterious outcomes.

There is no standardised definition or checklist to identify oral frailty but the one proposed by Tanaka et al. has been highly cited in our papers.⁷ Tanaka et al. defines oral frailty as functional limitations in ≥3 of six domains : few remaining teeth, decreased masticatory performance, decreased articulatory oral motor skills, lower maximum tongue pressure, subjective difficulty chewing hard foods, and subjective difficulty swallowing.⁸

We propose that there should be a consensus on the identification of oral frailty via case finding approach. Although there is yet to be a standardised approach in screening and identifying for oral frailty, based on the various tools found in this review, questions that can be asked to the elderly during routine visits can include if they are suffering from tooth loss, if they have difficulty chewing or swallowing food and if they have visited a dentist in the past 1 year.^7,9,45 These simple questions in addition to a bedside oral examination can give the clinician a clue to identify if oral frailty is a concern which can then prompt the referral to the relevant specialty for example gerodontology.⁸

Preventive measures for oral frailty that seek to preserve oral health would involve improving oral function on an individual basis and promoting community health education.³⁸ Oral health counselling was suggested by Kossioni et al. for care of teeth and dentures, preventing hyposalivation and xerostomia, lifestyle changes, dietary advice and regular dental checkups.⁴⁶

Multidisciplinary management of oral frailty and its associations are paramount to address the symptoms early.⁴⁷ As highlighted in the paper by Shiraishi et al., management involves oral rehabilitation, oral health education and oral health promotion.⁴⁸ We propose that it involves not just oral health education and promotion but a comprehensive review of the geriatric patient with a focus on physical, social and psychological factors. It requires a multi-pronged approach with collaboration between medical doctors, nurses, dentists and dental hygienists to identify and treat oral frailty.

Further research needs to be conducted to determine a standardised screening and diagnostic tool for oral frailty and how it impacts on determined outcome measures for the various geriatric syndromes. Most of the studies have been conducted in the Asian population and they were of a cross-sectional nature. More robust studies need to be performed in other countries outside of Asia. Collaborative work between general physicians, dentists, dieticians and geriatricians will be key for the above.

This scoping review is not without limitations. Firstly, hand searches and major textbooks were not included. Secondly, the search terms were not discussed with the librarian.

Conclusion

Oral frailty has been demonstrated to have wide-ranging associations and detrimental consequences from the realms of physical frailty to reduced cognition, mood and nutrition. Relevant information for example number of teeth and questions on self-perceived oral function can be easily obtained and incorporated into routine geriatric care. It is imperative that we take a closer look at this field and use this window of opportunity to provide optimal care for our patients. Addressing oral frailty involves a multidisciplinary approach, combining dental care, nutritional support, and attention to overall health to improve the quality of life for elderly individuals. With more studies in this area, it is hoped that we can investigate and tailor interventions for our geriatric population, thereby reducing the adverse outcomes and allowing them to age well and live well.

Supplemental Material

Supplemental Material - Oral frailty and outcomes: A scoping review

Supplemental Material for Oral frailty and outcomes: A scoping review by Wei Ting Foo, Sri Karpageshwary K and Angela Frances Hui Wen Yap in Proceedings of Singapore Healthcare.

Footnotes

Author contributions

Foo Wei Ting was involved in the conceptualization, article search, methodology and writing of original draft. K Sri Karpageshwary was involved in the article search, methodology, writing of original draft. Angela Frances Yap Hui Wen was involved in the conceptualization, article search, editing of final publication. All authors reviewed and edited the manuscript and approved the final version of the manuscript.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Wei Ting Foo

Supplemental Material

Supplemental material for this article is available online.

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