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Association of eating alone with oral frailty among community-dwelling older adults in Japan
Archives of Gerontology and Geriatrics 87 (2020) 104014
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Association of eating alone with oral frailty among community-dwelling older adults in Japan
T
Yuki Ohara*, Keiko Motokawa, Yutaka Watanabe, Maki Shirobe, Hiroki Inagaki, Yoshiko Motohashi, Ayako Edahiro, Hirohiko Hirano, Akihiko Kitamura, Shuichi Awata, Shoji Shinkai Research Team for Promoting Independence and Mental Health, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015, Tokyo, Japan
ARTICLE INFO
ABSTRACT
Keywords: Dietary habits Oral function Eating alone Older adults
Background: Because the oral cavity plays an important role as the first digestive organ, thus, decreased oral function such as oral frailty may negatively affect the nutritional status of older adults. However, few studies have examined the relationship between oral frailty and dietary habits. Objective: This cross-sectional study aimed to investigate the relationship between oral functions and dietary habits in a general population of older adults. Methods: Participants were 722 older adults (mean age, 79.1 ± 4.5 [standard deviation] years) who had participated in the Takashimadaira Study conducted in 2018, in Tokyo, Japan. Oral frailty among them was determined by a modified version of a well-known method originally proposed by other researchers. Dietary habits were evaluated based on two aspects: dietary variety and eating behavior (eating alone or together). The independent association between oral frailty and dietary habits was analyzed with an ordinal logistic regression model, controlling for important covariates. Results: Of the participants, 23.5 %, 57.2 % and 19.3 % were determined to have non-oral frailty, pre-oral frailty, and oral frailty, respectively. Eating alone (practiced by 36.0 % of the participants) was significantly associated with oral frailty status (adjusted odds ratio, 1.82 [95 % confidence interval, 1.14–2.90]) even after controlling for potential confounders including age, sex, body mass index, living arrangement, employment, chronic medical conditions, and depressive mood. Conclusions: We found a significant association between eating alone and oral frailty in a general population of Japanese older adults. Because of the strong association, further investigation of potential mechanisms is warranted.
1. Introduction The oral cavity performs various functions such as chewing, swallowing, and communication; these functions are closely related to quality of life in older adults (Enoki et al., 2014; Ohi et al., 2018; Takeshita et al., 2015). Several previous studies have reported that oral health and general health closely interact with each other, especially in older adults; oral health cannot be considered to be isolated from other aspects of the body’s functioning. In recent years, frailty has been regarded as one of the general health issues in super-aged societies. It is considered to be highly prevalent in populations of older adults and is one of the risk factors for
adverse health outcomes, such as mortality, institutionalization, falls, and hospitalization (Fried et al., 2001). Sarcopenia and undernutrition are components of the frailty cycle comprising psychiatric and social factors (Xue, Bandeen-Roche, Varadhan, Zhou, & Fried, 2008). The relationship between oral function and frailty has been reported by previous studies, and decreased chewing ability and oral motor skills have been recognized as independent factors associated with frailty (Iwasaki et al., 2018; Watanabe et al., 2017). Oral function consists of multiple functions such as mastication, swallowing, and motor dexterity. However, most previous studies have focused on individual oral functions, especially masticatory function. In recent years, the concept of “oral frailty” has been proposed, conceptualizing the age-related
Abbreviations: BMI, body mass index; CI, confidence interval; DVS, dietary variety score; GDS, Geriatric Depression Scale; MMSE-J, Mini-Mental State Examination Japanese version; ODK, oral diadochokinesis; OR, odds ratio; SD, standard deviation; TMIG-IC, Tokyo Metropolitan Institute of Gerontology Index of Competence ⁎ Corresponding author. E-mail address: [email protected] (Y. Ohara). https://doi.org/10.1016/j.archger.2020.104014 Received 5 November 2019; Received in revised form 31 December 2019; Accepted 17 January 2020 Available online 18 January 2020 0167-4943/ © 2020 Elsevier B.V. All rights reserved.
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deterioration process of oral function (Minakuchi et al., 2018; Tanaka et al., 2018). Oral frailty implies signs of decreased oral function, such as poor masticatory performance, reduced oral motor skills, difficulty swallowing, low lingual pressure, and a low number of present teeth. Thus, it is a comprehensive concept based on the diversity of oral functions (Tanaka et al., 2018). In a longitudinal study of Japanese community-dwelling older adults, Tanaka et al. reported that oral frailty predicted subsequent risks for physical frailty, need of long-term care, and mortality. Therefore, it is important to consider the effective maintenance or improvement of oral function among older adults as an important issue to achieve healthy aging. The oral cavity contains the first digestive organ, and decreased oral function and tooth loss have been proven to affect nutritional status (Inomata et al., 2017; Wakai et al., 2010) Meals are not only life-sustaining, but also associated with quality of life such as enjoyment of eating and socializing. In particular, dietary habits—such as the quality and diversity of the food consumed—and eating behaviors—such as eating alone or together—should be considered in addition to nutritional status in order to verify the relationship to oral function among community-dwelling older people. However, few studies have examined the association between oral frailty and dietary habits. Eating alone is one of the important components of dietary habits as a health issue among older population, because its association with depressive symptoms and mortality has been reported (Kuroda et al., 2015; Tani et al., 2018). Previous study revealed that eating alone was associated with frailty (Suthutvoravut, Tanaka, Takahashi, Akishita, & Iijima, 2019). Similarly, eating alone may also affect the severity of oral frailty but, to our knowledge, there have been no reports investigating its relevance. Therefore, the present study aimed to investigate the relationship between oral frailty status and dietary habits in a general population of older adults in Japan.
Fig. 1. Flowchart of study selection process.
2.2. Measurements Oral assessments were performed by well-trained dentists and dental hygienists. Prior to the study, the staff received instructions over the course of two hours from the authors regarding the appropriate method of data collection for each measurement for the purpose of calibration. Oral examinations comprised six measures including counting the number of present teeth, determining oral function, and self-assessed oral function. 2.3. Intra-oral examination
2. Methods
For the intra-oral examination, the number of present teeth was counted. Severely decayed and stump teeth were not considered as present teeth.
2.1. Study design and participants This cross-sectional study was conducted in 2018. Data were obtained from the Takashimadaira Study, a longitudinal cohort study conducted in a metropolitan area in Tokyo (Takashimadaira, Itabashiku). Data were collected through a series of interviews, questionnaires, and health examinations to gain information on topics like lifestyle, diet, overall health status, and physical function including oral health, cognitive function, social status, and demographics. A flow chart regarding details of recruitment of the participants is shown in Fig. 1. This project was initiated in 2016, and the details of this study have been described in a previous study (Igarashi et al., 2019) Power analysis for a logistic regression was conducted using G*power (version 3.1.9.4, Heinrich-Heine-Universität Düsseldorf, Germany) to determine a sufficient sample size of 0.80 and two-tailed test. Based on the aforementioned assumptions, the desired sample size was 135. The present comprehensive health survey was held at a community hall in December 2018 as the two-year follow-up for 1,248 older adults (506 men and 742 women) who had participated in the baseline survey in 2016. In total, 743 individuals (response rate: 59.5 %) participated in the 2018 survey. The study excluded those with missing information on oral function (n = 9) or the Mini-Mental State Examination Japanese version (MMSE-J) (n = 2), as well as those with decreased cognitive function (MMSE-J score < 18) (n = 12) for the purpose of ensuring the accuracy of the self-administered questionnaire. The analysis was conducted on the remaining dataset of 722 individuals (277 men [38.4 %] and 445 women [61.6 %], mean age ± standard deviation [SD]: 79.1 ± 4.5 years). This study was approved by the ethics committees of the Tokyo Metropolitan Institute of Gerontology (receipt number 28031, 30–33). Informed written consent was obtained from all participants.
2.4. Oral diadochokinesis (ODK) We conducted an ODK test, defined as the rate of maximal rapid syllable repetition, to evaluate articulatory oral motor skills at sites such as the lips, tongue tip, and tongue dorsum. Participants were asked to repeat each given syllable—/ta/—sequentially as fast as possible for 5 s. The number of repetitions per second was calculated as the repetition speed of the syllables (Watanabe et al., 2017). 2.5. Tongue muscle force Tongue muscle force, implying maximum tongue pressure, was measured using a hand-held balloon probe and a manometer (JMS, Hiroshima, Japan) (Yoshida et al., 2006). The participants were asked to sit in a relaxed position, place the balloon on their tongue, and hold the plastic pipe at the midpoint of their central incisors with their lips closed. They were then asked to compress the balloon onto their palates for approximately 7 s by maximum voluntary effort of the tongue. The maximum value of three records was defined as tongue muscle force. 2.6. Chewing ability Participants’ chewing ability was assessed by a color-changeable chewing gum (masticatory performance evaluating gum Xylitol; Lotte, Saitama, Japan) (Wada, Kawate, & Mizuma, 2017). The gum changes from yellowish-green to red when chewed. The red dye is pH-sensitive and changes color under neutral or alkaline conditions. Citric acid maintains the low internal pH of the yellowish-green gum before 2
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cerebrovascular disorder, heart disease, diabetes mellitus, dyslipidemia, osteoporosis, and cancer), and depressive mood based on the 15-item Geriatric Depression Scale (GDS-15) (range: 0–15; higher GDS scores indicated higher depressive mood) (Sugishita, Sugishita, Hemmi, Asada, & Tanigawa, 2017). Participants were interviewed to determine their medical history and information on other variables was collected through self-administered questionnaires.
chewing. During the course of chewing, the gum color changes to red because the yellow and blue dyes leach into the saliva and the red color appears as a result of citric acid elution. Changes in the color values of the gum reflect the comprehensive abilities of mastication, such as dental occlusion, salivary secretion, and tongue movements. The value of a* represents the degree of color between red and green. Positive values for a* indicate red. After chewing the gum 60 times at a rhythm of one chewing action per second, the chewed gum was flattened in polyethylene films by compression, before measuring the a* values using a colorimeter (CR-20; Konica-Minolta Sensing, Tokyo, Japan) and determining the mean values of three points for each of the a* values.
2.10. Data analysis For this study, we used the definition of oral frailty proposed by Tanaka et al., who adopted the cut-off value for objective data (Tanaka et al., 2018) (Table 1). “Non-oral frailty” reflected no poor status in any of the six targeted measures, “pre-oral frailty” reflected poor status in one or two measures, and “oral frailty” reflected poor status in three or more of the six targeted measures. With regard to the participants’ characteristics of non-oral frailty, pre-oral frailty, and oral frailty groups, the Jonckheere-Terpstra and the Mantel-Haenszel trend tests were used for comparisons of continuous and categorical variables, respectively. To examine the association between the severity of oral frailty and dietary habits, an ordinal logistic regression analysis was conducted. The independent variable was the severity of oral frailty (non-oral frailty, pre-oral frailty, and oral frailty), and dependent variables were eating alone and DVS. All analyses were performed using SPSS version 25.0 J (IBM Japan, Tokyo, Japan). The variance inflation factor was used to quantify the severity of multicollinearity. The level of significance was set at p < .05.
2.7. Self-assessed oral function We sought participants’ responses questions regarding oral function: “Do solid food?” and “Do you choke when response to these questions indicated swallowing, respectively.
to the following dichotomous you have difficulty in chewing drinking tea or soup?” A “yes” difficulties in mastication and
2.8. Dietary habits We assessed dietary habits in terms of dietary quality and eating behavior. The diversity of food intake was adopted as a measure of dietary quality, and eating alone was adopted as a measure of eating behavior. The variety of participants’ food intake indicated their dietary variety score (DVS), which was assessed using a self-administered questionnaire on the frequency of food consumption during one week. The questionnaire covered 10 main food groups: fish and shellfish, meat, eggs, milk, soybean/soybean products, green and yellow vegetables, potatoes, seaweeds, fruits, and fats and oils. Each response that stated “I have eaten every day” for each food group received a score of 1 with a possible maximum total score of 10 for the entire questionnaire (Kumagai et al., 2003). Eating alone was assessed using the question, “Do you usually have meal with others?” Participants were asked to select a response from five options: “I usually eat with someone,” “4–5 days a week,” “2–3 days a week,” “1 day a week,” or “I always eat alone.” We defined eating alone by participants’ responses of “1 day a week” and “I always eat alone.”
3. Results The results of simple tabulations on each item of oral function that served as a criterion for oral frailty are shown in Table 1 The highest observed rate of decreased oral function was found in masticatory performance as evaluated by chewing gum (38.9 %), followed by the number of present teeth (37.3 %). Table 2 lists the characteristics of study participants by severity of oral frailty. In total, 23.5 % of participants had non-oral frailty, 57.2 % had pre-oral frailty, and 19.3 % had oral frailty. The ratio of those who ate alone was 36.0 % among all participants. Participants in the oral frailty and pre-oral frailty groups also showed the following trends: significantly older age, lower food variety, higher percentage of eating alone, and higher scores on the GDS-15 (p < .05). On the other hand, no significant differences were observed with regard to gender, social status, or the presence of systemic diseases based on the severity of oral frailty. Regarding the comparison of food group by DVS, lack of daily intake of milk and green-yellow vegetables was significantly associated with the severity of oral frailty. Table 3 shows the results of the ordinal multiple logistic regression
2.9. Covariates Covariates included demographic factors (e.g., age and gender), body mass index (BMI) representing nutritional status, social status (e.g., years of education, employment status, and living alone), higher functional capacity as evaluated by the Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIG-IC), health behavior (e.g., smoking and drinking habits), medical history (e.g., hypertension, Table 1 Criteria of oral function and observation rate of decreased oral function.
Mean ( ± SD)
Prevalence
Criteria
Number of present teeth ODK (times/s)
19.5 6.2
( ± 9.2) ( ± 0.7)
269 (37.3 %) 73 (10.0 %)
33.4
( ± 8.2)
139 (19.3 %)
Chewing ability
13.5
( ± 5.6)
281 (38.9 %)
Difficulty masticating Difficulty swallowing
– –
– –
142 (19.7 %) 180 (24.9 %)
< 20 Male Female Male Female Male Female Yes Yes
Tongue muscle force (kPa)
Note. The cut-off value of each oral function was determined based on the report by Tanaka et al. (2018). SD: standard deviation. ODK: Oral diadochokinesis.
3
< 5.2 times/s < 5.4 times/s < 27.4 kPa < 26.5 kPa < 14.2 < 10.8
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Table 2 Comparison of participants’ characteristics and oral-frailty severity. Variables
Number or participants Basic attributes Age, years Sex, female Dietary habits Dietary variety score Food groups (consumed daily) Fish and shellfish Meat Eggs Milk Soybean/soybean products Green and yellow vegetables Potatoes Seaweeds Fruits Fats and oils Eating alone Body mass index, kg/m2 Social status Years of education, year Employed Living alone TMIG-IC, point Drinking alcohol Current smoker Medical history Hypertension Cerebrovascular disorder Heart disease Diabetes mellitus Dyslipidemia Osteoporosis Cancer GDS-15 score
Overall
Oral frailty status
722
P for trend
Non-oral frailty (0/6)
Pre-oral frailty (1–2/6)
Oral frailty (≥3/6)
170
(23.5 %)
413
(57.2 %)
139
(19.3 %)
79.1 445
± 4.5 (61.6 %)
78.2 110
± 4.1 (64.7 %)
78.8 252
± 4.2 (61.0 %)
81.3 83
± 5.1 (59.7 %)
< 0.001a 0.355 b
4.5
± 2.5
4.8
± 2.5
4.5
± 2.5
4.1
± 2.7
0.028
261 272 348 405 373 419 125 216 489 352 260 23.2
(36.1 %) (37.7 %) (48.2 %) (56.1 %) (51.7 %) (58.0 %) (17.3 %) (29.9 %) (67.7 %) (48.8 %) (36.0 %) ± 3.1
65 67 76 108 88 114 35 60 114 81 54 23.1
(38.2 %) (39.4 %) (44.7 %) (63.5 %) (51.8 %) (67.1 %) (20.6 %) (35.3 %) (67.1 %) (47.6 %) (31.8 %) ± 2.7
151 163 202 225 209 244 63 119 293 209 143 23.4
(36.6 %) (39.5 %) (48.9 %) (54.5 %) (50.6 %) (59.1 %) (15.3 %) (28.8 %) (70.9 %) (50.6 %) (34.6 %) ± 3.2
45 42 70 72 76 61 27 37 82 62 63 22.7
(32.4 %) (30.2 %) (50.4 %) (51.8 %) (54.7 %) (43.9 %) (19.4 %) (26.6 %) (59.0 %) (44.6 %) (45.3 %) ± 3.5
0.297 b 0.117 b 0.555 b 0.033 b 0.647 b < 0.001 0.692 b 0.088 b 0.180 b 0.658 b 0.017 b 0.230 a
12.8 128 285 12.1 335 44
± 2.5 (17.7 %) (39.5 %) ± 1.3 (46.4 %) (6.1 %)
12.8 35 103 12.4 83 10
± 2.3 (20.6 %) (60.6 %) ± 1.0 (48.8 %) (5.9 %)
13.0 76 252 12.1 196 26
± 2.6 (18.4 %) (61.0 %) ± 1.2 (47.5 %) (6.3 %)
12.3 17 82 11.8 56 8
± 2.5 (12.2 %) (59.0 %) ± 1.5 (40.3 %) (5.8 %)
0.101 a 0.062 b 0.794 b < 0.001a 0.150 b 0.979 b
365 53 171 84 301 196 130 3.5
(50.6 %) (7.3 %) (23.7 %) (11.6 %) (41.7 %) (27.1 %) (18.0 %) ± 3.2
77 11 34 12 69 38 34 2.7
(45.6 %) (6.5 %) (20.0 %) (7.1 %) (40.8 %) (22.4 %) (20.0 %) ± 2.7
217 32 101 54 175 110 74 3.4
(52.7 %) (7.7 %) (24.5 %) (13.1 %) (42.7 %) (26.6 %) (17.9 %) ± 3.1
71 10 36 18 57 48 22 4.8
(51.1 %) (7.2 %) (25.9 %) (12.9 %) (41.3 %) (34.5 %) (15.8 %) ± 3.6
0.293 b 0.781 b 0.221 b 0.088 b 0.907 b 0.018 b 0.341 b < 0.001a
a
b
Note. Continuous variables are presented as mean ± standard deviation. TMIG-IC: Tokyo Metropolitan Institute of Gerontology Index of Competence. GDS 0–15: Geriatric Depression Scale-15. a Jonckheere-Terpstra trend test. b Mantel-Haenszel trend test.
4. Discussion
Table 3 Multivariable model for the association between oral frailty and dietary habits.
Dietary variety score (per one increase) Eating alone (0: absence, 1: presence)
Adjusted OR†
95 % CI
P-value†
0.94 1.82
0.89 – 1.00 1.14 – 2.90
0.066 0.012
To our knowledge, this is the first large-scale study to examine the relationship between dietary habits and the severity of oral frailty among community-dwelling older adults in Japan. This study thus presents novel findings that have considered oral function from the comprehensive perspective of oral frailty and investigated its association with dietary habits. Principally, this study found eating alone to be significantly associated with oral frailty, rather than with dietary variety, even when controlling for living arrangements with others, employment status, and other social factors. Meals can provide valuable opportunities for socializing, whereby older adults build intimate interactions with others. The findings of the present study suggest that eating alone is associated with oral inactivity; in other words, oral function is lower due to the lack of conversations and fewer chewing actions when eating alone than when eating together. On the other hand, oral function may be affected by psychosocial factors because eating together plays critical roles not only in access to nutrients but also in communication and emotional expression with others. Previous studies have also reported that a reduction in the frequency of going out and depression were associated with oral health status (Ohara et al., 2015). The findings of this study reveal that social engagement factors—such as eating alone—rather than dietary variation—possibly affect oral frailty. Preventive strategies toward oral frailty aimed at
Note. This model was adjusted for age, sex, TMIG-IC, GDS score, and social status (employment, years of education, and living arrangement), body mass index, drinking and smoking habit, and presence of medical history. CI: confidence interval. GDS: Geriatric Depression Scale. TMIG-IC: Tokyo Metropolitan Institute of Gerontology Index of Competence. OR: odds ratio. † Adjusted odds ratios and P-values estimated using ordinal logistic regression model.
analysis with regard to the association between oral frailty and dietary habits. Even after adjusting for potential confounders including age, sex, living status, employment, medical history, and depressive symptoms, eating alone remained significantly associated with a higher odds ratio (OR) of the presence and severity of oral frailty (adjusted OR for the presence of eating alone 1.82, 95 % confidence interval 1.14 – 2.90, p = 0.012).
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maintaining oral health status would require multiple interventions, individual improvement of oral function, as well as group health education in communities, based on social relationships. The participants of the present study were older adults living in Japanese metropolitan areas, of whom more than 30 % often ate alone. It has been reported that in the older population, eating alone is influenced by depressive symptoms, happiness, nutritional status, and mortality, and it seems to be a major factor that influences healthy longevity among older persons (Tani et al., 2018; Wang et al., 2016). Locher, Robinson, Roth, Ritchie, and Burgio suggested that problems with eating in older adults were not simply limited to the presence or absence of cohabiting families (Locher, Robinson, Roth, Ritchie, & Burgio, 2005). Kuroda et al. reported that 6.8 % of older adults who lived with others ate alone, which was a significant factor associated with depression. (Kuroda et al., 2015) Because eating alone may possibly affect the quality of life among the population of older adults, with a rapidly aging society, strategies to prevent older adults from eating alone that consider psychosocial aspects should be taken into consideration. The multivariate analysis results showed no significant association between oral frailty and the diversity of food intake. However, previous studies have reported that occlusal force and salivation affect food intake and appropriate prosthodontic treatment contributes to the improvement of serum albumin (Inomata et al., 2014; Kanehisa, Yoshida, Taji, Akagawa, & Nakamura, 2009). The present study does not deny a relationship between oral function and nutrition. Further studies are required to investigate the relationship between oral frailty and nutritional status comprehensively. Oral frailty is a relatively new concept and although the findings are still limited, we found that the distribution of severe oral frailty is similar to that mentioned in previous reports (Tanaka et al., 2018). Although the voluntarily participants in this health survey had a high degree of independence in daily life, approximately 20 % of them had an overlap of oral hyopofunctions. The oral functions required to eat involve complex movements such as chewing and swallowing, as well as lip and tongue motor skills. In addition, eating behaviors comprise not only physiological exercise, but also psychosocial aspects such as motivation to eat, human engagement, and enjoyment of life (Iinuma et al., 2017; Nakata & Kawai, 2017) Although they complained about masticatory difficulty having increased, some of those whose masticatory ability objectively showed lowered difficulty claimed that the difficulty had doubled; this indicates that the participants’ evaluation and the objective evaluation did not always match, similar to a finding in a report by Takagi et al. (2017). In the present study, we employed the definition of oral frailty used by Tanaka et al., as it evaluates masticatory hypofunction both subjectively and objectively. Since participants in the oral frailty group were significantly older than those in the other groups, oral function seemed to be more susceptible to aging, which was similar to a finding from a previous report (Watanabe et al., 2017). This highlights the importance of having a long-term preventive strategy and oral function evaluations from an early stage, before the manifestation of symptoms of oral hypofunction. A previous study that demonstrated an association between tongue muscle force, social networks, and leisure activities suggested that eating with someone influenced the activation of oral function—such as promoting saliva secretion and enhancing tongue motor function—and can be expected to have a positive effect on depressive symptoms. Similarly, reports from some longitudinal studies suggested that poor dental health status may be a predictor of becoming housebound in the future as people get older, and it is therefore crucial to focus on the association between social engagement and oral health through dietary habits. Further studies including interventions targeting comprehensive health promotion and prevention of severe oral frailty in early stages are required. While it provides some insight to the condition of oral frailty, this
study also has some limitations: First, due to its cross-sectional design, it is difficult to infer a causal relationship. A prospective design is needed to investigate whether oral frailty affects dietary habits. Second, we divided eating behavior into only two categories. A previous study reported a dose-response relationship between health outcomes and the duration of eating alone, therefore suggesting that future studies should include more detailed information such as the duration of eating alone. Third the variables considered as confounding factors were limited; in particular, no consideration was given to physical function. In future studies, additional factors affecting dietary habits, such as physical function, economic status, and social capital, must be considered. 5. Conclusions In the present study, we found that eating alone was significantly associated with oral frailty status among community-dwelling older adults living in a metropolitan area in Tokyo. This association implies that oral health may be an important factor in not only nutritional status but also social function. Longitudinal studies are needed to examine the causal relationship between oral function and social factors such as social engagement and networks. Funding The study was supported by the Tokyo Metropolitan Government, the Tokyo Metropolitan Institute of Gerontology, and a Research Funding for Longevity Sciences (19-42) from the National Center for Geriatrics and Gerontology, Japan Agency for Medical Research and Development [Grant Number: JP 18dk0110019h0003, JP18dk0110018h0003], and Grants-in-Aid for Scientific Research [Grant Number: 16K11908, 17H02187, 18K09874], Japan. Declaration of Competing Interest None. Acknowledgments The authors acknowledge Editage (www.editage.com) for English language editing and publication support. References Enoki, K., Matsuda, K. I., Ikebe, K., Murai, S., Yoshida, M., Maeda, Y., ... Thomson, W. M. (2014). Influence of xerostomia on oral health-related quality of life in the elderly: A 5-year longitudinal study. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 117, 716–721. Fried, L. P., Tangen, C. M., Walston, J., Newman, A. B., Hirsch, C., Gottdiener, J., ... McBurnie, M. A. (2001). Frailty in older adults: Evidence for a phenotype. The Journals of Gerontology Series A, Biological Sciences and Medical Sciences, 56, M146–156. Igarashi, K., Watanabe, Y., Kugimiya, Y., Shirobe, M., Edahiro, A., Kaneda, K., ... Kawai, Y. (2019). Validity of a visual scoring method using gummy jelly for evaluating chewing efficiency in a large-scale epidemiological survey. Journal of Oral Rehabilitation, 46, 409–416. Iinuma, T., Arai, Y., Takayama, M., Takayama, M., Abe, Y., Osawa, Y., ... Gionhaku, N. (2017). Satisfaction with dietary life affects oral health-related quality of life and subjective well-being in very elderly people. Journal of Oral Science, 59, 207–213. Inomata, C., Ikebe, K., Kagawa, R., Okubo, H., Sasaki, S., Okada, T., ... Maeda, Y. (2014). Significance of occlusal force for dietary fibre and vitamin intakes in independently living 70-year-old Japanese: From SONIC Study. Journal of Dentistry, 42, 556–564. Inomata, C., Ikebe, K., Okubo, H., Takeshita, H., Mihara, Y., Hatta, K., ... Maeda, Y. (2017). Dietary intake is associated with occlusal force rather than number of teeth in 80-y-Old Japanese. JDR Clinical and Translational Research, 2, 187–197. Iwasaki, M., Kimura, Y., Sasiwongsaroj, K., Kettratad-Pruksapong, M., Suksudaj, S., Ishimoto, Y., ... Miyazaki, H. (2018). Association between objectively measured chewing ability and frailty: A cross-sectional study in central Thailand. Geriatrics & Gerontology International, 18, 860–866. Kanehisa, Y., Yoshida, M., Taji, T., Akagawa, Y., & Nakamura, H. (2009). Body weight and serum albumin change after prosthodontic treatment among institutionalized elderly in a long-term care geriatric hospital. Community Dentistry and Oral Epidemiology, 37, 534–538.
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Y. Ohara, et al. Kumagai, S., Watanabe, S., Shibata, H., Amano, H., Fujiwara, Y., Shinkai, S., ... Haga, H. (2003). Effects of dietary variety on declines in high-level functional capacity in elderly people living in a community. Nihon koshu eisei zasshi] Japanese Journal of Public Health, 50, 1117–1124. Kuroda, A., Tanaka, T., Hirano, H., Ohara, Y., Kikutani, T., Furuya, H., ... Iijima, K. (2015). Eating alone as social disengagement is strongly associated with depressive symptoms in Japanese community-dwelling older adults. Journal of the American Medical Directors Association, 16, 578–585. Locher, J. L., Robinson, C. O., Roth, D. L., Ritchie, C. S., & Burgio, K. L. (2005). The effect of the presence of others on caloric intake in homebound older adults. The Journals of Gerontology Series A, Biological Sciences and Medical Sciences, 60, 1475–1478. Minakuchi, S., Tsuga, K., Ikebe, K., Ueda, T., Tamura, F., Nagao, K., ... Sakurai, K. (2018). Oral hypofunction in the older population: Position paper of the Japanese Society of Gerodontology in 2016. Gerodontology, 35, 317–324. Nakata, R., & Kawai, N. (2017). The "social" facilitation of eating without the presence of others: Self-reflection on eating makes food taste better and people eat more. Physiology & Behavior, 179, 23–29. Ohara, Y., Hirano, H., Watanabe, Y., Obuchi, S., Yoshida, H., Fujiwara, Y., ... Mataki, S. (2015). Factors associated with self-rated oral health among community-dwelling older Japanese: A cross-sectional study. Geriatrics & Gerontology International, 15, 755–761. Ohi, T., Komiyama, T., Miyoshi, Y., Murakami, T., Tsuboi, A., Tomata, Y., ... Hattori, Y. (2018). Maximum occlusal force and incident functional disability in older adults: The Tsurugaya Project. JDR Clinical and Translational Research, 3, 195–202. Sugishita, K., Sugishita, M., Hemmi, I., Asada, T., & Tanigawa, T. (2017). A validity and reliability study of the Japanese version of the Geriatric Depression Scale 15 (GDS-15J). Clinical Gerontologist, 40, 233–240. Suthutvoravut, U., Tanaka, T., Takahashi, K., Akishita, M., & Iijima, K. (2019). Living with family yet eating alone is associated with frailty in community-dwelling older adults: The Kashiwa Study. The Journal of Frailty & Aging, 8, 198–204. Takagi, D., Watanabe, Y., Edahiro, A., Ohara, Y., Murakami, M., Murakami, K., ... Hirano, H. (2017). Factors affecting masticatory function of community-dwelling older
people: Investigation of the differences in the relevant factors for subjective and objective assessment. Gerodontology, 34, 357–364. Takeshita, H., Ikebe, K., Kagawa, R., Okada, T., Gondo, Y., Nakagawa, T., ... Maeda, Y. (2015). Association of personality traits with oral health-related quality of life independently of objective oral health status: A study of community-dwelling elderly Japanese. Journal of Dentistry, 43, 342–349. Tanaka, T., Takahashi, K., Hirano, H., Kikutani, T., Watanabe, Y., Ohara, Y., ... Iijima, K. (2018). Oral frailty as a risk factor for physical frailty and mortality in communitydwelling elderly. The Journals of Gerontology Series A, Biological Sciences and Medical Sciences, 73, 1661–1667. Tani, Y., Kondo, N., Noma, H., Miyaguni, Y., Saito, M., & Kondo, K. (2018). Eating alone yet living with others is associated with mortality in older men: The JAGES Cohort Survey. The Journals of Gerontology Series B, Psychological Sciences and Social Sciences, 73, 1330–1334. Wada, S., Kawate, N., & Mizuma, M. (2017). What type of food can older adults masticate? Evaluation of mastication performance using color-changeable chewing gum. Dysphagia, 32, 636–643. Wakai, K., Naito, M., Naito, T., Kojima, M., Nakagaki, H., Umemura, O., ... Kawamura, T. (2010). Tooth loss and intakes of nutrients and foods: A nationwide survey of Japanese dentists. Community Dentistry and Oral Epidemiology, 38, 43–49. Wang, X., Shen, W., Wang, C., Zhang, X., Xiao, Y., He, F., ... Lin, J. (2016). Association between eating alone and depressive symptom in elders: A cross-sectional study. BMC Geriatrics, 16, 19. Watanabe, Y., Hirano, H., Arai, H., Morishita, S., Ohara, Y., Edahiro, A., ... Suzuki, T. (2017). Relationship between frailty and oral function in community-dwelling elderly adults. Journal of the American Geriatrics Society, 65, 66–76. Xue, Q. L., Bandeen-Roche, K., Varadhan, R., Zhou, J., & Fried, L. P. (2008). Initial manifestations of frailty criteria and the development of frailty phenotype in the Women’s Health and Aging Study II. The Journals of Gerontology Series A, Biological Sciences and Medical Sciences, 63, 984–990. Yoshida, M., Kikutani, T., Tsuga, K., Utanohara, Y., Hayashi, R., & Akagawa, Y. (2006). Decreased tongue pressure reflects symptom of dysphagia. Dysphagia, 21, 61–65.
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Association of eating alone with oral frailty among community-dwelling older adults in Japan
T
Yuki Ohara*, Keiko Motokawa, Yutaka Watanabe, Maki Shirobe, Hiroki Inagaki, Yoshiko Motohashi, Ayako Edahiro, Hirohiko Hirano, Akihiko Kitamura, Shuichi Awata, Shoji Shinkai Research Team for Promoting Independence and Mental Health, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, 173-0015, Tokyo, Japan
ARTICLE INFO
ABSTRACT
Keywords: Dietary habits Oral function Eating alone Older adults
Background: Because the oral cavity plays an important role as the first digestive organ, thus, decreased oral function such as oral frailty may negatively affect the nutritional status of older adults. However, few studies have examined the relationship between oral frailty and dietary habits. Objective: This cross-sectional study aimed to investigate the relationship between oral functions and dietary habits in a general population of older adults. Methods: Participants were 722 older adults (mean age, 79.1 ± 4.5 [standard deviation] years) who had participated in the Takashimadaira Study conducted in 2018, in Tokyo, Japan. Oral frailty among them was determined by a modified version of a well-known method originally proposed by other researchers. Dietary habits were evaluated based on two aspects: dietary variety and eating behavior (eating alone or together). The independent association between oral frailty and dietary habits was analyzed with an ordinal logistic regression model, controlling for important covariates. Results: Of the participants, 23.5 %, 57.2 % and 19.3 % were determined to have non-oral frailty, pre-oral frailty, and oral frailty, respectively. Eating alone (practiced by 36.0 % of the participants) was significantly associated with oral frailty status (adjusted odds ratio, 1.82 [95 % confidence interval, 1.14–2.90]) even after controlling for potential confounders including age, sex, body mass index, living arrangement, employment, chronic medical conditions, and depressive mood. Conclusions: We found a significant association between eating alone and oral frailty in a general population of Japanese older adults. Because of the strong association, further investigation of potential mechanisms is warranted.
1. Introduction The oral cavity performs various functions such as chewing, swallowing, and communication; these functions are closely related to quality of life in older adults (Enoki et al., 2014; Ohi et al., 2018; Takeshita et al., 2015). Several previous studies have reported that oral health and general health closely interact with each other, especially in older adults; oral health cannot be considered to be isolated from other aspects of the body’s functioning. In recent years, frailty has been regarded as one of the general health issues in super-aged societies. It is considered to be highly prevalent in populations of older adults and is one of the risk factors for
adverse health outcomes, such as mortality, institutionalization, falls, and hospitalization (Fried et al., 2001). Sarcopenia and undernutrition are components of the frailty cycle comprising psychiatric and social factors (Xue, Bandeen-Roche, Varadhan, Zhou, & Fried, 2008). The relationship between oral function and frailty has been reported by previous studies, and decreased chewing ability and oral motor skills have been recognized as independent factors associated with frailty (Iwasaki et al., 2018; Watanabe et al., 2017). Oral function consists of multiple functions such as mastication, swallowing, and motor dexterity. However, most previous studies have focused on individual oral functions, especially masticatory function. In recent years, the concept of “oral frailty” has been proposed, conceptualizing the age-related
Abbreviations: BMI, body mass index; CI, confidence interval; DVS, dietary variety score; GDS, Geriatric Depression Scale; MMSE-J, Mini-Mental State Examination Japanese version; ODK, oral diadochokinesis; OR, odds ratio; SD, standard deviation; TMIG-IC, Tokyo Metropolitan Institute of Gerontology Index of Competence ⁎ Corresponding author. E-mail address: [email protected] (Y. Ohara). https://doi.org/10.1016/j.archger.2020.104014 Received 5 November 2019; Received in revised form 31 December 2019; Accepted 17 January 2020 Available online 18 January 2020 0167-4943/ © 2020 Elsevier B.V. All rights reserved.
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deterioration process of oral function (Minakuchi et al., 2018; Tanaka et al., 2018). Oral frailty implies signs of decreased oral function, such as poor masticatory performance, reduced oral motor skills, difficulty swallowing, low lingual pressure, and a low number of present teeth. Thus, it is a comprehensive concept based on the diversity of oral functions (Tanaka et al., 2018). In a longitudinal study of Japanese community-dwelling older adults, Tanaka et al. reported that oral frailty predicted subsequent risks for physical frailty, need of long-term care, and mortality. Therefore, it is important to consider the effective maintenance or improvement of oral function among older adults as an important issue to achieve healthy aging. The oral cavity contains the first digestive organ, and decreased oral function and tooth loss have been proven to affect nutritional status (Inomata et al., 2017; Wakai et al., 2010) Meals are not only life-sustaining, but also associated with quality of life such as enjoyment of eating and socializing. In particular, dietary habits—such as the quality and diversity of the food consumed—and eating behaviors—such as eating alone or together—should be considered in addition to nutritional status in order to verify the relationship to oral function among community-dwelling older people. However, few studies have examined the association between oral frailty and dietary habits. Eating alone is one of the important components of dietary habits as a health issue among older population, because its association with depressive symptoms and mortality has been reported (Kuroda et al., 2015; Tani et al., 2018). Previous study revealed that eating alone was associated with frailty (Suthutvoravut, Tanaka, Takahashi, Akishita, & Iijima, 2019). Similarly, eating alone may also affect the severity of oral frailty but, to our knowledge, there have been no reports investigating its relevance. Therefore, the present study aimed to investigate the relationship between oral frailty status and dietary habits in a general population of older adults in Japan.
Fig. 1. Flowchart of study selection process.
2.2. Measurements Oral assessments were performed by well-trained dentists and dental hygienists. Prior to the study, the staff received instructions over the course of two hours from the authors regarding the appropriate method of data collection for each measurement for the purpose of calibration. Oral examinations comprised six measures including counting the number of present teeth, determining oral function, and self-assessed oral function. 2.3. Intra-oral examination
2. Methods
For the intra-oral examination, the number of present teeth was counted. Severely decayed and stump teeth were not considered as present teeth.
2.1. Study design and participants This cross-sectional study was conducted in 2018. Data were obtained from the Takashimadaira Study, a longitudinal cohort study conducted in a metropolitan area in Tokyo (Takashimadaira, Itabashiku). Data were collected through a series of interviews, questionnaires, and health examinations to gain information on topics like lifestyle, diet, overall health status, and physical function including oral health, cognitive function, social status, and demographics. A flow chart regarding details of recruitment of the participants is shown in Fig. 1. This project was initiated in 2016, and the details of this study have been described in a previous study (Igarashi et al., 2019) Power analysis for a logistic regression was conducted using G*power (version 3.1.9.4, Heinrich-Heine-Universität Düsseldorf, Germany) to determine a sufficient sample size of 0.80 and two-tailed test. Based on the aforementioned assumptions, the desired sample size was 135. The present comprehensive health survey was held at a community hall in December 2018 as the two-year follow-up for 1,248 older adults (506 men and 742 women) who had participated in the baseline survey in 2016. In total, 743 individuals (response rate: 59.5 %) participated in the 2018 survey. The study excluded those with missing information on oral function (n = 9) or the Mini-Mental State Examination Japanese version (MMSE-J) (n = 2), as well as those with decreased cognitive function (MMSE-J score < 18) (n = 12) for the purpose of ensuring the accuracy of the self-administered questionnaire. The analysis was conducted on the remaining dataset of 722 individuals (277 men [38.4 %] and 445 women [61.6 %], mean age ± standard deviation [SD]: 79.1 ± 4.5 years). This study was approved by the ethics committees of the Tokyo Metropolitan Institute of Gerontology (receipt number 28031, 30–33). Informed written consent was obtained from all participants.
2.4. Oral diadochokinesis (ODK) We conducted an ODK test, defined as the rate of maximal rapid syllable repetition, to evaluate articulatory oral motor skills at sites such as the lips, tongue tip, and tongue dorsum. Participants were asked to repeat each given syllable—/ta/—sequentially as fast as possible for 5 s. The number of repetitions per second was calculated as the repetition speed of the syllables (Watanabe et al., 2017). 2.5. Tongue muscle force Tongue muscle force, implying maximum tongue pressure, was measured using a hand-held balloon probe and a manometer (JMS, Hiroshima, Japan) (Yoshida et al., 2006). The participants were asked to sit in a relaxed position, place the balloon on their tongue, and hold the plastic pipe at the midpoint of their central incisors with their lips closed. They were then asked to compress the balloon onto their palates for approximately 7 s by maximum voluntary effort of the tongue. The maximum value of three records was defined as tongue muscle force. 2.6. Chewing ability Participants’ chewing ability was assessed by a color-changeable chewing gum (masticatory performance evaluating gum Xylitol; Lotte, Saitama, Japan) (Wada, Kawate, & Mizuma, 2017). The gum changes from yellowish-green to red when chewed. The red dye is pH-sensitive and changes color under neutral or alkaline conditions. Citric acid maintains the low internal pH of the yellowish-green gum before 2
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cerebrovascular disorder, heart disease, diabetes mellitus, dyslipidemia, osteoporosis, and cancer), and depressive mood based on the 15-item Geriatric Depression Scale (GDS-15) (range: 0–15; higher GDS scores indicated higher depressive mood) (Sugishita, Sugishita, Hemmi, Asada, & Tanigawa, 2017). Participants were interviewed to determine their medical history and information on other variables was collected through self-administered questionnaires.
chewing. During the course of chewing, the gum color changes to red because the yellow and blue dyes leach into the saliva and the red color appears as a result of citric acid elution. Changes in the color values of the gum reflect the comprehensive abilities of mastication, such as dental occlusion, salivary secretion, and tongue movements. The value of a* represents the degree of color between red and green. Positive values for a* indicate red. After chewing the gum 60 times at a rhythm of one chewing action per second, the chewed gum was flattened in polyethylene films by compression, before measuring the a* values using a colorimeter (CR-20; Konica-Minolta Sensing, Tokyo, Japan) and determining the mean values of three points for each of the a* values.
2.10. Data analysis For this study, we used the definition of oral frailty proposed by Tanaka et al., who adopted the cut-off value for objective data (Tanaka et al., 2018) (Table 1). “Non-oral frailty” reflected no poor status in any of the six targeted measures, “pre-oral frailty” reflected poor status in one or two measures, and “oral frailty” reflected poor status in three or more of the six targeted measures. With regard to the participants’ characteristics of non-oral frailty, pre-oral frailty, and oral frailty groups, the Jonckheere-Terpstra and the Mantel-Haenszel trend tests were used for comparisons of continuous and categorical variables, respectively. To examine the association between the severity of oral frailty and dietary habits, an ordinal logistic regression analysis was conducted. The independent variable was the severity of oral frailty (non-oral frailty, pre-oral frailty, and oral frailty), and dependent variables were eating alone and DVS. All analyses were performed using SPSS version 25.0 J (IBM Japan, Tokyo, Japan). The variance inflation factor was used to quantify the severity of multicollinearity. The level of significance was set at p < .05.
2.7. Self-assessed oral function We sought participants’ responses questions regarding oral function: “Do solid food?” and “Do you choke when response to these questions indicated swallowing, respectively.
to the following dichotomous you have difficulty in chewing drinking tea or soup?” A “yes” difficulties in mastication and
2.8. Dietary habits We assessed dietary habits in terms of dietary quality and eating behavior. The diversity of food intake was adopted as a measure of dietary quality, and eating alone was adopted as a measure of eating behavior. The variety of participants’ food intake indicated their dietary variety score (DVS), which was assessed using a self-administered questionnaire on the frequency of food consumption during one week. The questionnaire covered 10 main food groups: fish and shellfish, meat, eggs, milk, soybean/soybean products, green and yellow vegetables, potatoes, seaweeds, fruits, and fats and oils. Each response that stated “I have eaten every day” for each food group received a score of 1 with a possible maximum total score of 10 for the entire questionnaire (Kumagai et al., 2003). Eating alone was assessed using the question, “Do you usually have meal with others?” Participants were asked to select a response from five options: “I usually eat with someone,” “4–5 days a week,” “2–3 days a week,” “1 day a week,” or “I always eat alone.” We defined eating alone by participants’ responses of “1 day a week” and “I always eat alone.”
3. Results The results of simple tabulations on each item of oral function that served as a criterion for oral frailty are shown in Table 1 The highest observed rate of decreased oral function was found in masticatory performance as evaluated by chewing gum (38.9 %), followed by the number of present teeth (37.3 %). Table 2 lists the characteristics of study participants by severity of oral frailty. In total, 23.5 % of participants had non-oral frailty, 57.2 % had pre-oral frailty, and 19.3 % had oral frailty. The ratio of those who ate alone was 36.0 % among all participants. Participants in the oral frailty and pre-oral frailty groups also showed the following trends: significantly older age, lower food variety, higher percentage of eating alone, and higher scores on the GDS-15 (p < .05). On the other hand, no significant differences were observed with regard to gender, social status, or the presence of systemic diseases based on the severity of oral frailty. Regarding the comparison of food group by DVS, lack of daily intake of milk and green-yellow vegetables was significantly associated with the severity of oral frailty. Table 3 shows the results of the ordinal multiple logistic regression
2.9. Covariates Covariates included demographic factors (e.g., age and gender), body mass index (BMI) representing nutritional status, social status (e.g., years of education, employment status, and living alone), higher functional capacity as evaluated by the Tokyo Metropolitan Institute of Gerontology Index of Competence (TMIG-IC), health behavior (e.g., smoking and drinking habits), medical history (e.g., hypertension, Table 1 Criteria of oral function and observation rate of decreased oral function.
Mean ( ± SD)
Prevalence
Criteria
Number of present teeth ODK (times/s)
19.5 6.2
( ± 9.2) ( ± 0.7)
269 (37.3 %) 73 (10.0 %)
33.4
( ± 8.2)
139 (19.3 %)
Chewing ability
13.5
( ± 5.6)
281 (38.9 %)
Difficulty masticating Difficulty swallowing
– –
– –
142 (19.7 %) 180 (24.9 %)
< 20 Male Female Male Female Male Female Yes Yes
Tongue muscle force (kPa)
Note. The cut-off value of each oral function was determined based on the report by Tanaka et al. (2018). SD: standard deviation. ODK: Oral diadochokinesis.
3
< 5.2 times/s < 5.4 times/s < 27.4 kPa < 26.5 kPa < 14.2 < 10.8
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Table 2 Comparison of participants’ characteristics and oral-frailty severity. Variables
Number or participants Basic attributes Age, years Sex, female Dietary habits Dietary variety score Food groups (consumed daily) Fish and shellfish Meat Eggs Milk Soybean/soybean products Green and yellow vegetables Potatoes Seaweeds Fruits Fats and oils Eating alone Body mass index, kg/m2 Social status Years of education, year Employed Living alone TMIG-IC, point Drinking alcohol Current smoker Medical history Hypertension Cerebrovascular disorder Heart disease Diabetes mellitus Dyslipidemia Osteoporosis Cancer GDS-15 score
Overall
Oral frailty status
722
P for trend
Non-oral frailty (0/6)
Pre-oral frailty (1–2/6)
Oral frailty (≥3/6)
170
(23.5 %)
413
(57.2 %)
139
(19.3 %)
79.1 445
± 4.5 (61.6 %)
78.2 110
± 4.1 (64.7 %)
78.8 252
± 4.2 (61.0 %)
81.3 83
± 5.1 (59.7 %)
< 0.001a 0.355 b
4.5
± 2.5
4.8
± 2.5
4.5
± 2.5
4.1
± 2.7
0.028
261 272 348 405 373 419 125 216 489 352 260 23.2
(36.1 %) (37.7 %) (48.2 %) (56.1 %) (51.7 %) (58.0 %) (17.3 %) (29.9 %) (67.7 %) (48.8 %) (36.0 %) ± 3.1
65 67 76 108 88 114 35 60 114 81 54 23.1
(38.2 %) (39.4 %) (44.7 %) (63.5 %) (51.8 %) (67.1 %) (20.6 %) (35.3 %) (67.1 %) (47.6 %) (31.8 %) ± 2.7
151 163 202 225 209 244 63 119 293 209 143 23.4
(36.6 %) (39.5 %) (48.9 %) (54.5 %) (50.6 %) (59.1 %) (15.3 %) (28.8 %) (70.9 %) (50.6 %) (34.6 %) ± 3.2
45 42 70 72 76 61 27 37 82 62 63 22.7
(32.4 %) (30.2 %) (50.4 %) (51.8 %) (54.7 %) (43.9 %) (19.4 %) (26.6 %) (59.0 %) (44.6 %) (45.3 %) ± 3.5
0.297 b 0.117 b 0.555 b 0.033 b 0.647 b < 0.001 0.692 b 0.088 b 0.180 b 0.658 b 0.017 b 0.230 a
12.8 128 285 12.1 335 44
± 2.5 (17.7 %) (39.5 %) ± 1.3 (46.4 %) (6.1 %)
12.8 35 103 12.4 83 10
± 2.3 (20.6 %) (60.6 %) ± 1.0 (48.8 %) (5.9 %)
13.0 76 252 12.1 196 26
± 2.6 (18.4 %) (61.0 %) ± 1.2 (47.5 %) (6.3 %)
12.3 17 82 11.8 56 8
± 2.5 (12.2 %) (59.0 %) ± 1.5 (40.3 %) (5.8 %)
0.101 a 0.062 b 0.794 b < 0.001a 0.150 b 0.979 b
365 53 171 84 301 196 130 3.5
(50.6 %) (7.3 %) (23.7 %) (11.6 %) (41.7 %) (27.1 %) (18.0 %) ± 3.2
77 11 34 12 69 38 34 2.7
(45.6 %) (6.5 %) (20.0 %) (7.1 %) (40.8 %) (22.4 %) (20.0 %) ± 2.7
217 32 101 54 175 110 74 3.4
(52.7 %) (7.7 %) (24.5 %) (13.1 %) (42.7 %) (26.6 %) (17.9 %) ± 3.1
71 10 36 18 57 48 22 4.8
(51.1 %) (7.2 %) (25.9 %) (12.9 %) (41.3 %) (34.5 %) (15.8 %) ± 3.6
0.293 b 0.781 b 0.221 b 0.088 b 0.907 b 0.018 b 0.341 b < 0.001a
a
b
Note. Continuous variables are presented as mean ± standard deviation. TMIG-IC: Tokyo Metropolitan Institute of Gerontology Index of Competence. GDS 0–15: Geriatric Depression Scale-15. a Jonckheere-Terpstra trend test. b Mantel-Haenszel trend test.
4. Discussion
Table 3 Multivariable model for the association between oral frailty and dietary habits.
Dietary variety score (per one increase) Eating alone (0: absence, 1: presence)
Adjusted OR†
95 % CI
P-value†
0.94 1.82
0.89 – 1.00 1.14 – 2.90
0.066 0.012
To our knowledge, this is the first large-scale study to examine the relationship between dietary habits and the severity of oral frailty among community-dwelling older adults in Japan. This study thus presents novel findings that have considered oral function from the comprehensive perspective of oral frailty and investigated its association with dietary habits. Principally, this study found eating alone to be significantly associated with oral frailty, rather than with dietary variety, even when controlling for living arrangements with others, employment status, and other social factors. Meals can provide valuable opportunities for socializing, whereby older adults build intimate interactions with others. The findings of the present study suggest that eating alone is associated with oral inactivity; in other words, oral function is lower due to the lack of conversations and fewer chewing actions when eating alone than when eating together. On the other hand, oral function may be affected by psychosocial factors because eating together plays critical roles not only in access to nutrients but also in communication and emotional expression with others. Previous studies have also reported that a reduction in the frequency of going out and depression were associated with oral health status (Ohara et al., 2015). The findings of this study reveal that social engagement factors—such as eating alone—rather than dietary variation—possibly affect oral frailty. Preventive strategies toward oral frailty aimed at
Note. This model was adjusted for age, sex, TMIG-IC, GDS score, and social status (employment, years of education, and living arrangement), body mass index, drinking and smoking habit, and presence of medical history. CI: confidence interval. GDS: Geriatric Depression Scale. TMIG-IC: Tokyo Metropolitan Institute of Gerontology Index of Competence. OR: odds ratio. † Adjusted odds ratios and P-values estimated using ordinal logistic regression model.
analysis with regard to the association between oral frailty and dietary habits. Even after adjusting for potential confounders including age, sex, living status, employment, medical history, and depressive symptoms, eating alone remained significantly associated with a higher odds ratio (OR) of the presence and severity of oral frailty (adjusted OR for the presence of eating alone 1.82, 95 % confidence interval 1.14 – 2.90, p = 0.012).
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maintaining oral health status would require multiple interventions, individual improvement of oral function, as well as group health education in communities, based on social relationships. The participants of the present study were older adults living in Japanese metropolitan areas, of whom more than 30 % often ate alone. It has been reported that in the older population, eating alone is influenced by depressive symptoms, happiness, nutritional status, and mortality, and it seems to be a major factor that influences healthy longevity among older persons (Tani et al., 2018; Wang et al., 2016). Locher, Robinson, Roth, Ritchie, and Burgio suggested that problems with eating in older adults were not simply limited to the presence or absence of cohabiting families (Locher, Robinson, Roth, Ritchie, & Burgio, 2005). Kuroda et al. reported that 6.8 % of older adults who lived with others ate alone, which was a significant factor associated with depression. (Kuroda et al., 2015) Because eating alone may possibly affect the quality of life among the population of older adults, with a rapidly aging society, strategies to prevent older adults from eating alone that consider psychosocial aspects should be taken into consideration. The multivariate analysis results showed no significant association between oral frailty and the diversity of food intake. However, previous studies have reported that occlusal force and salivation affect food intake and appropriate prosthodontic treatment contributes to the improvement of serum albumin (Inomata et al., 2014; Kanehisa, Yoshida, Taji, Akagawa, & Nakamura, 2009). The present study does not deny a relationship between oral function and nutrition. Further studies are required to investigate the relationship between oral frailty and nutritional status comprehensively. Oral frailty is a relatively new concept and although the findings are still limited, we found that the distribution of severe oral frailty is similar to that mentioned in previous reports (Tanaka et al., 2018). Although the voluntarily participants in this health survey had a high degree of independence in daily life, approximately 20 % of them had an overlap of oral hyopofunctions. The oral functions required to eat involve complex movements such as chewing and swallowing, as well as lip and tongue motor skills. In addition, eating behaviors comprise not only physiological exercise, but also psychosocial aspects such as motivation to eat, human engagement, and enjoyment of life (Iinuma et al., 2017; Nakata & Kawai, 2017) Although they complained about masticatory difficulty having increased, some of those whose masticatory ability objectively showed lowered difficulty claimed that the difficulty had doubled; this indicates that the participants’ evaluation and the objective evaluation did not always match, similar to a finding in a report by Takagi et al. (2017). In the present study, we employed the definition of oral frailty used by Tanaka et al., as it evaluates masticatory hypofunction both subjectively and objectively. Since participants in the oral frailty group were significantly older than those in the other groups, oral function seemed to be more susceptible to aging, which was similar to a finding from a previous report (Watanabe et al., 2017). This highlights the importance of having a long-term preventive strategy and oral function evaluations from an early stage, before the manifestation of symptoms of oral hypofunction. A previous study that demonstrated an association between tongue muscle force, social networks, and leisure activities suggested that eating with someone influenced the activation of oral function—such as promoting saliva secretion and enhancing tongue motor function—and can be expected to have a positive effect on depressive symptoms. Similarly, reports from some longitudinal studies suggested that poor dental health status may be a predictor of becoming housebound in the future as people get older, and it is therefore crucial to focus on the association between social engagement and oral health through dietary habits. Further studies including interventions targeting comprehensive health promotion and prevention of severe oral frailty in early stages are required. While it provides some insight to the condition of oral frailty, this
study also has some limitations: First, due to its cross-sectional design, it is difficult to infer a causal relationship. A prospective design is needed to investigate whether oral frailty affects dietary habits. Second, we divided eating behavior into only two categories. A previous study reported a dose-response relationship between health outcomes and the duration of eating alone, therefore suggesting that future studies should include more detailed information such as the duration of eating alone. Third the variables considered as confounding factors were limited; in particular, no consideration was given to physical function. In future studies, additional factors affecting dietary habits, such as physical function, economic status, and social capital, must be considered. 5. Conclusions In the present study, we found that eating alone was significantly associated with oral frailty status among community-dwelling older adults living in a metropolitan area in Tokyo. This association implies that oral health may be an important factor in not only nutritional status but also social function. Longitudinal studies are needed to examine the causal relationship between oral function and social factors such as social engagement and networks. Funding The study was supported by the Tokyo Metropolitan Government, the Tokyo Metropolitan Institute of Gerontology, and a Research Funding for Longevity Sciences (19-42) from the National Center for Geriatrics and Gerontology, Japan Agency for Medical Research and Development [Grant Number: JP 18dk0110019h0003, JP18dk0110018h0003], and Grants-in-Aid for Scientific Research [Grant Number: 16K11908, 17H02187, 18K09874], Japan. Declaration of Competing Interest None. Acknowledgments The authors acknowledge Editage (www.editage.com) for English language editing and publication support. References Enoki, K., Matsuda, K. I., Ikebe, K., Murai, S., Yoshida, M., Maeda, Y., ... Thomson, W. M. (2014). Influence of xerostomia on oral health-related quality of life in the elderly: A 5-year longitudinal study. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 117, 716–721. Fried, L. P., Tangen, C. M., Walston, J., Newman, A. B., Hirsch, C., Gottdiener, J., ... McBurnie, M. A. (2001). Frailty in older adults: Evidence for a phenotype. The Journals of Gerontology Series A, Biological Sciences and Medical Sciences, 56, M146–156. Igarashi, K., Watanabe, Y., Kugimiya, Y., Shirobe, M., Edahiro, A., Kaneda, K., ... Kawai, Y. (2019). Validity of a visual scoring method using gummy jelly for evaluating chewing efficiency in a large-scale epidemiological survey. Journal of Oral Rehabilitation, 46, 409–416. Iinuma, T., Arai, Y., Takayama, M., Takayama, M., Abe, Y., Osawa, Y., ... Gionhaku, N. (2017). Satisfaction with dietary life affects oral health-related quality of life and subjective well-being in very elderly people. Journal of Oral Science, 59, 207–213. Inomata, C., Ikebe, K., Kagawa, R., Okubo, H., Sasaki, S., Okada, T., ... Maeda, Y. (2014). Significance of occlusal force for dietary fibre and vitamin intakes in independently living 70-year-old Japanese: From SONIC Study. Journal of Dentistry, 42, 556–564. Inomata, C., Ikebe, K., Okubo, H., Takeshita, H., Mihara, Y., Hatta, K., ... Maeda, Y. (2017). Dietary intake is associated with occlusal force rather than number of teeth in 80-y-Old Japanese. JDR Clinical and Translational Research, 2, 187–197. Iwasaki, M., Kimura, Y., Sasiwongsaroj, K., Kettratad-Pruksapong, M., Suksudaj, S., Ishimoto, Y., ... Miyazaki, H. (2018). Association between objectively measured chewing ability and frailty: A cross-sectional study in central Thailand. Geriatrics & Gerontology International, 18, 860–866. Kanehisa, Y., Yoshida, M., Taji, T., Akagawa, Y., & Nakamura, H. (2009). Body weight and serum albumin change after prosthodontic treatment among institutionalized elderly in a long-term care geriatric hospital. Community Dentistry and Oral Epidemiology, 37, 534–538.
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