Association between oral health and nutritional status among older patients requiring long-term care who received home-visit dental care

Abstract

Purpose: This study examined the association between oral health and nutritional status among older patients receiving home-visit dental care.

Methods: This study enrolled 110 older patients (age ≥65 years) requiring long-term care who received home-visit dental care. The oral health indicators evaluated included number of teeth, occlusal support, number of functional teeth, tongue pressure, tongue coating index (TCI), and rinsing ability. Nutritional indicators included skeletal muscle mass index (SMI) and the mini-nutritional assessment short-form (MNA-SF). A multivariate modified Poisson regression analysis (adjusted for age, sex, medical history, care level, and housing type) was used to calculate prevalence ratios and 95% confidence intervals (CIs).

Results: The prevalence ratio for low SMI was not significantly higher for patients with ≥20 teeth than for those with 1-19 or no teeth. Number of teeth was not significantly associated with MNA-SF score. A high TCI score (2.15, 95% CI: 1.07-4.32) and poor rinsing ability (2.32, 95% CI: 1.25-4.30) were significantly associated with low SMI. High TCI scores were associated with low scores in MNA-SF categories (1.25, 95% CI: 1.01-1.55).

Conclusion: TCI and rinsing ability, rather than number of teeth, were associated with nutritional status in older patients requiring long-term care.

Introduction

Oral health is a key determinant of dietary intake and nutritional status in older adults [1,2]. The relationship between oral health and nutritional status is important in the etiology of several adverse health outcomes associated with oral health, including frailty, functional disability, dementia, and death [3,4,5,6].

Oral health is a multidimensional indicator that includes information on (i) oral function, such as masticatory efficiency, tongue pressure, motor function of the tongue and lips, and xerostomia; (ii) oral morphological indicators, such as tooth loss and occlusal support, a foundational indicator of vigorous oral function; (iii) dental diseases caused by poor oral hygiene, such as tooth decay and periodontal disease; and (iv) oral health behavior, including preventive practices, such as frequency of tooth brushing and regular dental visits.

Previous studies have examined associations of indicators of oral function and morphology (rather than oral hygiene outcomes such as periodontal disease and decayed teeth) with dietary and nutritional indicators [3,7,8,9,10,11,12]. These associations have been investigated in several settings, such as cohort studies of older people living in the community and in nursing homes. However, most of these studies analyzed data from hospitalized patients and outpatients receiving dental treatment; few relied on clinical data [13,14].

In Japan, the need for older persons requiring long-term or end-of-life care to receive dental care in their homes and nursing homes is expected to increase as the population ages [Ministry of Health Labour and Welfare, 2017] [15]. Furthermore, patients receiving home-visit dental care in Japan often undergo treatment with removable dentures in addition to requiring care for oral hygiene. Consequently, such patients are at risk of being malnourished owing to deterioration of masticatory function [9] [Nakane A et al., Jpn J Gerodont 35: 150-157, 2020].

In the home-visit dental care setting, information is limited on whether oral health is associated with nutritional status and what oral health indicators are associated with nutritional status in older people requiring long-term care. Therefore, this study explored the association between oral health and nutritional status in older adults requiring long-term care in home-visit dental care settings.

Materials and Methods

Participants

This cross-sectional study analyzed clinical data from older adults (age ≥65 years) requiring long-term care who received home-visit dental care in Fukushima Prefecture, Japan, from July 2020 to March 2023. The participants were 110 patients residing in their homes or nursing homes. Patients incapable of oral intake were excluded. Data were only collected after informed consent for the research was obtained from the patients or their legal representatives, such as their families.

Oral health examination

A dentist (YF) evaluated patients’ oral health, including number of teeth, posterior occlusal support, number of functional teeth, tongue pressure, tongue coating index (TCI), and rinsing ability. Number of teeth, excluding residual root teeth, was classified as ≥20, 1-19, or 0 teeth. Posterior occlusal support was evaluated using the Eichner Index. Participants with at least one occlusal support area were classified as having posterior occlusal support, while those with no retaining occlusal support area were classified as lacking posterior occlusal support [16]. Functional teeth were defined as the sum of the number of teeth and artificial teeth, such as removable partial dentures, pontics in fixed partial dentures, and dental implants [17].

Tongue pressure was evaluated with a tongue pressure-measuring device (TPM-01, JMS Co., Ltd., Hiroshima, Japan), and participants were categorized as exerting a pressure of ≥30 kPa or <30 kPa, as in a previous study [18]. Some participants were unable to complete the tongue pressure test because of medical conditions, such as severe dementia, that limited their understanding of how to complete the test. These patients were classified separately as “difficult to measure.”

The TCI, an indicator of oral hygiene status, was evaluated by examining the tongue surface [19]. The dentist assigned scores for the extent of tongue coating in each of the nine tongue sections. The participants were categorized based on whether the ratio of their total score to the maximum score was ≥50% or <50% [18].

Rinsing ability was categorized as (1) swishes a sip of water around in the mouth, (2) retains a sip of water in the mouth to some extent, or (3) lacks the ability to retain a sip of water in the mouth. Rinsing ability was assessed using a method developed in Japan that quantifies oral care independence while brushing, wearing dentures, and rinsing the mouth. Patients who could swish a sip of water around in their mouth were deemed to have vigorous rinsing ability, while those in the other categories were classified as having reduced rinsing ability [20].

Nutritional assessment

The skeletal muscle mass index (SMI) and mini-nutritional assessment short-form (MNA-SF) scores were collected for nutritional assessment. The SMI was evaluated by bioelectrical impedance analysis using an InbodyS10 device (Inbody Japan Inc., Tokyo, Japan) [21]. Participants were categorized into two groups according to the 2019 Asian Working Group for Sarcopenia criteria (men: <7.0 kg/m²; women: <5.7 kg/m²) [22].

The MNA-SF is a screening tool that evaluates the nutritional status of older adults and comprises six sections on (i) food intake, (ii) weight loss, (iii) mobility, (iv) acute diseases, (v) neurological problems, and (vi) body mass index [23]. The reliability and validity of the MNA-SF were sufficient for evaluating participants with dementia [24]. Participants with scores of <12 or ≥12 points were classified as having decreased nutritional status or being well-nourished, respectively [25].

Other variables

Information on age, sex, medical history (stroke, dementia, and pneumonia), care level, and type of housing was collected from patients’ medical records. Medical history was consolidated into a single variable that indicated whether patients have ≥1 disease or no diseases. The care level was based on the Japanese long-term care insurance classification, which specifies specific care levels from level one, the mildest level, to level seven, the severest level [26].

Statistical analysis

Characteristics based on the SMI and MNA-SF scores were analyzed using the Wilcoxon rank-sum test for continuous variables, and Fisher’s exact test was used for categorical variables. The prevalence ratio (PR) and 95% confidence interval (CI) of the decline in nutritional status were calculated using multivariate modified Poisson regression analysis, adjusted for age, sex, medical history, care level, and type of housing.

Categorical variables with missing data were recorded by reassigning missing values into separate “missing” categories to maximize the sample size of the participants included in the analysis. All statistical analyses were performed using Stata (version 17.0; Stata Corp LLC, College Station, TX, USA), and the level of statistical significance was set at α = 0.05 (two-tailed).

Results

Among the 110 patients, the mean age ± standard deviation (SD) was 83.1 ± 8.4 years. The means ± SD for number of teeth and care level were 12.1 ± 9.6 and 4.7 ± 1.7, respectively. Of all patients, 34 and 85 had low SMI and MNA-SF scores, respectively. Care level, TCI, and rinsing ability significantly differed in relation to SMI status. Similarly, care level, tongue pressure, TCI, and rinsing ability significantly differed in relation to MNA-SF status (Table 1). No patient scored ≥12 points on the MNA-SF and none lacked the ability to rinse.

After adjusting for age, sex, medical history, housing, and care level, multivariate Poisson regression analysis of oral health status in relation to SMI and MNA-SF status revealed that the PR for low SMI was not significantly higher in patients with 1-19 teeth (1.16, 95% CI: 0.48-2.81) and no teeth (1.32, 95% CI: 0.46-3.78) than in those with ≥20 teeth (Tables 2, 3).

The PR for low MNA-SF status was not significantly higher in patients with 1-19 teeth (1.04, 95% CI: 0.81-1.32) and no teeth (1.06, 95% CI: 0.78-1.43) than in those with ≥20 teeth. The PRs for low SMI (1.18, 95% CI: 0.64-2.17) and MNA-SF scores (0.98, 95% CI: 0.79-1.20) were not significantly higher in patients lacking posterior occlusal support than in those with retained posterior occlusal support. The PR for low SMI was significantly higher in patients with high TCI scores than in those with low TCI scores (2.15, 95% CI: 1.07-4.32) and in patients lacking rinsing ability than in those with vigorous rinsing ability (2.32, 95% CI: 1.25-4.30). The PR for low MNA-SF status was significantly higher in patients with high TCI scores (1.25, 95% CI: 1.01-1.55) than in those with low TCI scores.

Table 1 Characteristics of patients who received home-visit dental care, by nutritional status (n = 110)

	Overall (n = 110)	SMI		P-value	MNA-SF		P-value*
		retained (n = 76)	decreased (n = 34)		retained (n = 25)	decreased (n = 85)
Age, years, median (IQR)	85 (76-91)	82 (73-90)	87 (80-91)	0.12	84 (75-92)	85 (77-90)	0.95
Male, %	37.3	36.8	38.2	0.99	36.0	37.7	0.99
Stroke, %	38.2	31.6	52.9	0.06	32.0	40.0	0.64
Dementia, %	30.9	30.3	32.4	0.83	16.0	35.3	0.09
Pneumonia, %	9.01	5.26	17.7	0.07	12.0	8.24	0.69
Type of housing
patient’s home, %	66.4	72.4	52.9	0.05	72.0	64.7	0.63
nursing home, %	33.6	27.6	47.1		28.0	35.3
Care level, mean, median (IQR)	5 (3-7)	4 (3-6)	6 (5-7)	<0.01	4 (3-5)	5 (4-6)	<0.01
Number of teeth, median (IQR)	11 (3-21)	14 (3-23)	6 (2-18)	0.05	10 (1-21)	11 (4-20)	0.65
Number of functional teeth, median (IQR)	28 (13-28)	28 (24-28)	27 (18-28)	0.18	27 (24-28)	28 (23-28)	0.61
Lack of posterior occlusal support, %	50.0	41.2	59.2	0.17	52.0	49.4	0.99
Decreased tongue pressure (<30 kPa), %	53.6	59.2	41.2	0.17	72.0	48.2	<0.01
TCI (≥50), %	51.9	42.1	73.5	<0.01	32.0	57.7	0.04
Lack of rinsing ability, %	30.9	19.7	55.9	<0.01	0.0	40.0	<0.01

^*P-values were obtained using the Wilcoxon rank sum test for continuous variables and Fisher’s exact test for categorical variables. IQR: interquartile range; MNA-SF: mini-nutritional assessment short-form; SMI: skeletal muscle mass index; TCI: tongue coating index.

 

Table 2 Association of oral health variables with skeletal muscle mass index

Variables	Unadjusted PRs (95% CIs)	P-valuea	Adjusted PRs (95% CIs)	P-valuea
Number of teeth
≥20	1.00		1.00
1-19	1.68 (0.80-3.54)	0.173	1.16 (0.48-2.81)	0.739
0	1.57 (0.62-3.99)	0.341	1.32 (0.46-3.78)	0.606
Posterior occlusal support area
≥1	1.00		1.00
0	1.43 (0.80-2.54)	0.223	1.18 (0.64-2.17)	0.590
Functional teeth (for each additional tooth)	0.97 (0.94-0.99)	0.010	0.97 (0.94-1.01)	0.102
Tongue pressure (kPa)
≥30	1.00		1.00
<30	0.77 (0.30-1.97)	0.588	0.68 (0.28-1.69)	0.411
Difficult to measure	1.37 (0.56-3.37)	0.495	0.81 (0.28-2.36)	0.703
TCI (%)
<50	1.00		1.00
≥50	2.58 (1.33-5.03)	0.005	2.15 (1.07-4.32)	0.032
Rinsing abilityb
1	1.00		1.00
≥2	2.83 (1.64-4.88)	<0.001	2.32 (1.25-4.30)	0.007

^aEach exposure variable was calculated separately. ^b1: swishes a sip of water around in the mouth; 2: retains a sip of water in the mouth to some extent; 3: lacks the ability to retain a sip of water in the mouth. Adjusted for age, sex, medical history (stroke, dementia, and pneumonia), care level, and housing type. CI: confidence interval; PR: prevalence ratio; TCI: tongue coating index

 

Table 3 Association of oral health variables with mini-nutritional assessment short-form score

Variables	Unadjusted PRs (95% CIs)	P-valuea	Adjusted PRs (95% CIs)	P-valuea
Number of teeth
≥20	1.00		1.00
1-19	1.03 (0.81-1.30)	0.812	1.04 (0.81-1.32)	0.775
0	1.03 (0.75-1.41)	0.870	1.06 (0.78-1.43)	0.718
Posterior occlusal support area
≥1	1.00		1.00
0	0.98 (0.80-1.20)	0.821	0.98 (0.79-1.20)	0.824
Functional teeth (for each additional tooth)	0.99 (0.98-0.99)	< 0.001	0.99 (0.98-1.00)	0.007
Tongue pressure (kPa)
≥30	1.00		1.00
<30	1.13 (0.71-1.80)	0.608	1.19 (0.74-1.91)	0.468
Difficult to measure	1.54 (0.99-3.37)	0.054	1.76 (1.04-2.96)	0.035
TCI (%)
<50	1.00		1.00
≥50	1.27 (1.02-1.57)	0.031	1.25 (1.01-1.55)	0.039
Rinsing abilityb
1	1.00		1.00
≥2	n/a	n/a	n/a	n/a

^aEach exposure variable was calculated separately. ^b1: swishes a sip of water around in the mouth; 2: retains a sip of water in the mouth to some extent; 3: lacks the ability to retain a sip of water in the mouth. Adjusted for age, sex, medical history (stroke, dementia, and pneumonia), care level, and housing type. CI: confidence interval; PR: prevalence ratio; TCI, tongue coating index

Discussion

This study used clinical data from home dental care visits to examine the association of oral health and nutritional status with two nutritional indicators among older adults receiving long-term care. The findings suggest that oral health is associated with SMI, an indicator of muscle mass, in this population. Morphological indicators of oral health, such as number of teeth and posterior occlusal support, were not associated with nutritional indicators after adjusting for age, sex, medical history, care level, and type of housing. However, TCI and rinsing ability were associated with nutritional indicators.

Clinical data from home-visit dental care patients requiring long-term care show that tooth loss was not associated with nutritional status, which contrasts with the findings of previous studies of community-dwelling and dental clinic outpatients [14,27]. While the association between tooth loss and nutritional status in older adults requiring long-term care remains controversial [28,29], some studies reported that tooth loss was not associated with nutritional status. Future research, including systematic reviews and meta-analyses, should further investigate this association in dependent older adults, such as those requiring long-term care. Additionally, given the limited sample size of this clinical study, the potential mechanism underlying this lack of association in older people requiring long-term care should be explored in future studies with larger sample sizes and a broader range of variables, including environmental factors such as family and caregiver information.

This study revealed an association between TCI, rinsing ability, and nutritional status. TCI is considered an indicator of oral hygiene; however, a previous study reported that tongue coating was associated with tongue motor function [30]. In this context, tongue motor function based on the TCI could be used to evaluate the extent of tongue motion, although not tongue power. A prior study also indicated that an oral functional training intervention, including tongue motion, was associated with decreased tongue coating. While TCI could be a potential proxy indicator of tongue motor function, a previous study provided a safer, more straightforward measurement of tongue motor function [31]. Rinsing effectively prevents oral disease [32], and vigorous rinsing ability requires adequate muscle mass and coordination of the lips, buccinator, and tongue. Previous research has demonstrated that vigorous activity of the lips, buccinator, and tongue is associated with nutritional intake [33]. The present findings suggest that, as compared with oral morphological indicators such as tooth loss and occlusal support, indicators of oral function such as TCI as a measure of tongue motor function and rinsing ability might be more closely associated with nutritional status in older people requiring long-term care who receive home-visit dental care.

Although a previous study found that low tongue pressure was linked to malnutrition [34], this study did not observe such an association. The present study focused on older patients requiring long-term care, 30.9% of whom had dementia and 38.2% of whom had a history of stroke. These factors likely contributed to the difficulty that 34.5% of patients experienced in completing tongue pressure test procedures, even though a well-trained dentist conducted the tests. Research indicating that patients with dementia struggle to understand instructions [35] suggests that these findings should be interpreted with caution owing to potential misclassification.

The present study evaluated the nutritional status of older patients in a home-visit dental care setting. The SMI, a phenotypic indicator of the Global Leadership Initiative on Malnutrition (GLIM) criteria [36], indicated that 30.9% of older patients had decreased nutritional status. In addition, the MNA-SF, a screening indicator of malnutrition, indicated that 77.3% were at risk of malnutrition or malnourished. In a study of a Japanese nursing home, MNA-SF scores indicated that 73.1% of residents were at risk of malnutrition or malnourished [10], as compared with 38.2% of residents in a nursing home in Italy [37]. Descriptive data from home-visit dental care settings on different aspects of patient’s nutritional status (i.e., SMI and MNA-SF) may guide dental teams in assessing patients’ nutritional status.

This study had some limitations. First, it was conducted in a single dental clinic. Therefore, the generalizability of the results is limited. Second, evaluating causal relationships is difficult in a cross-sectional study. Third, because of the small sample size, analyzing association between rinsing ability and MNA-SF score was challenging. However, this study yielded important data on the association between rinsing ability and SMI, an indicator of the GLIM criteria. Because of the small sample size, medical histories of stroke, dementia, and pneumonia were combined into one variable, thereby limiting information that might have been gained by adjusting for each disease separately.

TCI and rinsing ability, rather than number of teeth or posterior occlusal support, were associated with the nutritional status of older adults requiring long-term care who received home-visit dental care.

Ethical Statements

The study protocol was approved by the Institutional Review Board of the Tohoku University Graduate School of Dentistry (No. 2019-3-036). All experiments involving human participants were conducted in accordance with the principles of the Declaration of Helsinki.

Conflicts of Interest

The authors declare no conflicts of interest.

Funding

This study was partially supported by JSPS KAKENHI (grant numbers: 18K09674, 22K10070, 22K10093, and 23K09476).

References

• 1.  Sheiham A, Steele JG, Marcenes W, Lowe C, Finch S, Bates CJ et al. (2001) The relationship among dental status, nutrient intake, and nutritional status in older people. J Dent Res 80, 408-413. doi: 10.1177/00220345010800020201
• 2.  Hussein S, Kantawalla RF, Dickie S, Suarez-Durall P, Enciso R, Mulligan R (2022) Association of oral health and mini nutritional assessment in older adults: a systematic review with meta-analyses. J Prosthodont Res 66, 208-220. doi: 10.2186/jpr.JPR_D_20_00207
• 3.  Komiyama T, Ohi T, Miyoshi Y, Murakami T, Tsuboi A, Tomata Y et al. (2016) Association between tooth loss, receipt of dental care, and functional disability in an elderly Japanese population: the Tsurugaya project. J Am Geriatr Soc 64, 2495-2502. doi: 10.1111/jgs.14390
• 4.  Fereshtehnejad SM, Garcia-Ptacek S, Religa D, Holmer J, Buhlin K, Eriksdotter M et al. (2018) Dental care utilization in patients with different types of dementia: a longitudinal nationwide study of 58,037 individuals. Alzheimers Dement 14, 10-19. doi: 10.1016/j.jalz.2017.05.004
• 5.  Ohi T, Komiyama T, Miyoshi Y, Murakami T, Tsuboi A, Tomata Y et al. (2020) The association between bilateral maximum occlusal force and all-cause mortality among community-dwelling older adults: the Tsurugaya project. J Prosthodont Res 64, 289-295. doi: 10.1016/j.jpor.2019.08.005
• 6.  Hakeem FF, Bernabé E, Sabbah W (2021) Association between oral health and frailty among American older adults. J Am Med Dir Assoc 22, 559-563.e2. doi: 10.1016/j.jamda.2020.07.023
• 7.  El Osta N, Hennequin M, Tubert-Jeannin S, Abboud Naaman NB, El Osta L, Geahchan N (2014) The pertinence of oral health indicators in nutritional studies in the elderly. Clin Nutr 33, 316-321. doi: 10.1016/j.clnu.2013.05.012
• 8.  Poisson P, Laffond T, Campos S, Dupuis V, Bourdel-Marchasson I (2016) Relationships between oral health, dysphagia and undernutrition in hospitalised elderly patients. Gerodontology 33, 161-168. doi: 10.1111/ger.12123
• 9.  Suzuki H, Kanazawa M, Komagamine Y, Iwaki M, Jo A, Amagai N et al. (2018) The effect of new complete denture fabrication and simplified dietary advice on nutrient intake and masticatory function of edentulous elderly: a randomized-controlled trial. Clin Nutr 37, 1441-1447. doi: 10.1016/j.clnu.2017.07.022
• 10.  Izumi M, Sonoki K, Ohta Y, Fukuhara M, Nagata M, Akifusa S (2020) Impact of tongue pressure and peak expiratory flow rate on nutritional status of older residents of nursing homes in Japan: a cross-sectional study. J Nutr Health Aging 24, 512-517. doi: 10.1007/s12603-020-1347-y
• 11.  Tani A, Mizutani S, Kishimoto H, Oku S, Iyota K, Chu T et al. (2023) The impact of nutrition and oral function exercise on among community-dwelling older people. Nutrients 15, 1607. doi: 10.3390/nu15071607
• 12.  Xu KH, Li L, Jia SL, Li Q, Hao JX, Ma S et al. (2023) Association of tooth loss and diet quality with acceleration of aging: evidence from NHANES. Am J Med 136, 773-779.e4. doi: 10.1016/j.amjmed.2023.04.008
• 13.  Maeda K, Akagi J (2015) Decreased tongue pressure is associated with sarcopenia and sarcopenic dysphagia in the elderly. Dysphagia 30, 80-87. doi: 10.1007/s00455-014-9577-y
• 14.  Takahashi M, Maeda K, Wakabayashi H (2018) Prevalence of sarcopenia and association with oral health-related quality of life and oral health status in older dental clinic outpatients. Geriatr Gerontol Int 18, 915-921. doi: 10.1111/ggi.13279
• 15.  Taniguchi Y, Iwagami M, Jin X, Sakata N, Sato M, Watanabe T et al. (2022) National trends in the proportion of in-hospital deaths by cause of death among older adults with long-term care: a nationwide observational study in Japan from 2007 to 2017. BMC Geriatr 22, 6. doi: 10.1186/s12877-021-02700-1
• 16.  Ito W, Komiyama T, Ohi T, Hiratsuka T, Matsuyama S, Sone T et al. (2021) Relationship between oral health and fractures in community-dwelling older Japanese adults. J Am Med Dir Assoc 22, 1184-1189.e1. doi: 10.1016/j.jamda.2021.01.058
• 17.  Han JH, Lee HJ, Han JW, Suh SW, Lee JR, Byun S et al. (2020) Loss of functional dentition is associated with cognitive impairment. J Alzheimers Dis 73, 1313-1320. doi: 10.3233/JAD-190971
• 18.  Minakuchi S, Tsuga K, Ikebe K, Ueda T, Tamura F, Nagao K et al. (2018) Oral hypofunction in the older population: position paper of the Japanese Society of Gerodontology in 2016. Gerodontology 35, 317-324. doi: 10.1111/ger.12347
• 19.  Shimizu T, Ueda T, Sakurai K (2007) New method for evaluation of tongue-coating status. J Oral Rehabil 34, 442-447. doi: 10.1111/j.1365-2842.2007.01733.x
• 20.  Tomuro K (2004) Oral home telecare tutorials for the community-dwelling elderly. J Med Dent Sci 51, 165-171.
• 21.  Momoki C, Habu D, Ogura J, Tada A, Hasei A, Sakurai K et al. (2017) Relationships between sarcopenia and household status and locomotive syndrome in a community-dwelling elderly women in Japan. Geriatr Gerontol Int 17, 54-60. doi: 10.1111/ggi.12674
• 22.  Chen LK, Woo J, Assantachai P, Auyeung TW, Chou MY, Iijima K et al. (2020) Asian Working Group for Sarcopenia: 2019 consensus update on sarcopenia diagnosis and treatment. J Am Med Dir Assoc 21, 300-307.e2. doi: 10.1016/j.jamda.2019.12.012
• 23.  Rubenstein LZ, Harker JO, Salvà A, Guigoz Y, Vellas B (2001) Screening for undernutrition in geriatric practice: developing the short-form mini-nutritional assessment (MNA-SF). J Gerontol A Biol Sci Med Sci 56, M366-M372. doi: 10.1093/gerona/56.6.m366
• 24.  Kimura A, Sugimoto T, Kitamori K, Saji N, Niida S, Toba K et al. (2019) Malnutrition is associated with behavioral and psychiatric symptoms of dementia in older women with mild cognitive impairment and early-stage Alzheimer’s disease. Nutrients 11, 1951. doi: 10.3390/nu11081951
• 25.  Lindmark U, Jansson H, Lannering C, Johansson L (2018) Oral Health matters for the nutritional status of older persons-A population-based study. J Clin Nurs 27, 1143-1152. doi: 10.1111/jocn.14146
• 26.  Tsutsui T, Muramatsu N (2007) Japan’s universal long-term care system reform of 2005: containing costs and realizing a vision. J Am Geriatr Soc 55, 1458-1463. doi: 10.1111/j.1532-5415.2007.01281.x
• 27.  Zelig R, Goldstein S, Touger-Decker R, Firestone E, Golden A, Johnson Z et al. (2022) Tooth loss and nutritional status in older adults: a systematic review and meta-analysis. JDR Clin Trans Res 7, 4-15. doi: 10.1177/2380084420981016
• 28.  Furuta M, Komiya-Nonaka M, Akifusa S, Shimazaki Y, Adachi M, Kinoshita T et al. (2013) Interrelationship of oral health status, swallowing function, nutritional status, and cognitive ability with activities of daily living in Japanese elderly people receiving home care services due to physical disabilities. Community Dent Oral Epidemiol 41, 173-181. doi: 10.1111/cdoe.12000
• 29.  Saarela RK, Soini H, Hiltunen K, Muurinen S, Suominen M, Pitkälä K (2014) Dentition status, malnutrition and mortality among older service housing residents. J Nutr Health Aging 18, 34-38. doi: 10.1007/s12603-013-0358-3
• 30.  Kikutani T, Tamura F, Nishiwaki K, Suda M, Kayanaka H, Machida R et al. (2009) The degree of tongue-coating reflects lingual motor function in the elderly. Gerodontology 26, 291-296. doi: 10.1111/j.1741-2358.2008.00258.x
• 31.  Nagashima K, Kikutani T, Takahashi N, Kato Y, Sagawa K, Tohara T et al. (2022) Development of the Sakiika transport test: a practical screening method for patients with oral-phase dysphagia. J Prosthodont Res 66, 409-415. doi: 10.2186/jpr.JPR_D_20_00290
• 32.  Wyatt CC, MacEntee MI (2004) Caries management for institutionalized elders using fluoride and chlorhexidine mouthrinses. Community Dent Oral Epidemiol 32, 322-328. doi: 10.1111/j.1600-0528.2004.00176.x
• 33.  Nishi K, Kanouchi H, Tanaka A, Nakamura M, Hamada T, Mishima Y et al. (2021) Relationship between oral hypofunction, and protein intake: a cross-sectional study in local community-dwelling adults. Nutrients 13, 4377. doi: 10.3390/nu13124377
• 34.  Abe A, Nakayama A, Otsuka Y, Shibata K, Matsui Y, Ito Y et al. (2023) Relationship of preoperative oral hypofunction with prognostic nutritional index in gastric cancer: a case-control retrospective study. PLoS One 18, e0283911. doi: 10.1371/journal.pone.0283911
• 35.  Sawaya Y, Ishizaka M, Kubo A, Shiba T, Sato T, Onoda K et al. (2020) Absolute reliability of tongue pressure measurement in young healthy adults and elderly patients with certification of needing long-term care or support. Geriatr Gerontol Int 20, 488-493. doi: 10.1111/ggi.13902
• 36.  Cederholm T, Jensen GL, Correia MITD, Gonzalez MC, Fukushima R, Higashiguchi T et al. (2019) GLIM criteria for the diagnosis of malnutrition - a consensus report from the global clinical nutrition community. J Cachexia Sarcopenia Muscle 10, 207-217. doi: 10.1002/jcsm.12383
• 37.  Valmorbida E, Trevisan C, Imoscopi A, Mazzochin M, Manzato E, Sergi G (2020) Malnutrition is associated with increased risk of hospital admission and death in the first 18 months of institutionalization. Clin Nutr 39, 3687-3694. doi: 10.1016/j.clnu.2020.03.029