Relationship between vertical hyoid bone position and swallowing function in older adults

Abstract

Purpose: The purpose of this study was to investigate swallowing function of older adults with lowered hyoid bone position.

Methods: A total of 60 older adults (23 males and 37 females, mean age: 70.1 years) with no diagnosed dysphagia participated in the study. Participants were divided into two groups (High and Low group) based on the anterior point of the hyoid bone (H) with respect to the line connecting the most inferior and anterior point on the corpus of the third cervical vertebra (C3) and Menton (Me). Swallowing function was measured using the Repetitive Saliva Swallow Test (RSST), the Eating Assessment Tool (EAT-10), jaw-opening force (JOF) and tongue pressure (TP). Each group was studied for its relationship to swallowing function. Additionally, the RSST of males and females in the Low group were compared.

Results: Males in the Low group had a significantly higher JOF (P = 0.009) in the RSST ≥ 5 group than in the RSST < 5 group. Females in the Low group had no measurements that showed significant differences between the RSST ≥ 4 and RSST < 4 groups.

Conclusion: JOF may affect swallowing function in older males with lowered hyoid bone position.

Introduction

Older adults are reported to be prone to frailty before requiring nursing care [1,2]. Frailty [3] is characterized by an increased vulnerability to health problems due to various age-related functional changes and declining physiological functions. Because frailty is reversible, its early identification and appropriate intervention are necessary [3]. Oral frailty, a term derived from the combination of the words ‘oral’ and ‘frailty’, has been proposed as the intermediate state between healthy and impaired oral function [4,5]. The progression of oral frailty decreases the ability of older adults to swallow, making them more likely to suffer from aspiration pneumonia and a reduced ability to ingest food, resulting in poor nutritional status [6,7]. Therefore, oral frailty is considered an early symptom of generalized frailty [8]. Findings from previous intervention studies suggest that early assessment of oral frailty signs and appropriate countermeasures may slow or even ameliorate the decline in oral function [9]. It is expected that early diagnosis and intervention against oral frailty will not only prevent dysphagia and aspiration pneumonia but also prevent older adults from progressing into generalized frailty [10].

Oral frailty development is associated with decreasing activity of various muscles, including perioral muscles (orbicularis oris, buccal) and swallowing-related muscles (tongue, suprahyoid). In particular, the suprahyoid muscle group has an important role in the opening of the mouth during mastication and in traction of the hyoid bone anteriorly and upwardly during swallowing to open the esophageal inlet [11]. The hyoid bone is the only bone in the human body that does not articulate with other bones and is supported by muscles. Consequently, the hyoid bone position changes due to the dysfunction of the attached muscles. The hyoid bone position is important in the assessment of swallowing-related muscles [12]. It declines with age, and when the hyoid bone declines, so does the function of swallowing-related muscles and swallowing function [13].

Currently, the Repetitive Saliva Swallow Test (RSST) [14] and the Eating Assessment Tool (EAT-10) [15,16] are used as screening methods for dysphagia. RSST has a sensitivity of 0.90 in detecting aspiration, while EAT-10 is effective in identifying individuals at risk for dysphagia. Both tests are effective as “dysphagia” screening tests, but no reliable method has been established for oral frailty screening, which represents a preliminary stage of dysphagia.

Older adults with intact swallowing function are often observed among those who exhibit lowered hyoid bone position. It was hypothesized that older adults who maintain swallowing function despite lowered hyoid bone position may have specific characteristics compared to those with decreased swallowing function. Clarifying these characteristics might reveal risks of swallowing dysfunction that have been missed by screening tests.

Although some studies have investigated the relationship between the position of the hyoid bone and swallowing function in older adults and those with dysphagia [17,18], no studies have focused on those with lowered hyoid bone position. Therefore, the purpose of this study was to investigate swallowing function of older adults with lowered hyoid bone position living in the community.

Materials and Methods

Participants

Sixty participants were recruited between February 2023 and July 2024. They were either patients who visited the outpatient dental clinic of Tokushima University Hospital or employees of the hospital. Participants were divided into three groups (Group A, B, and C) based on age. Group A consisted of 20 participants aged 50 to 64 years (8 males and 12 females, mean age: 59.2 years), group B consisted of 20 participants aged 65 to 74 years (10 males and 10 females, mean age: 69.6 years), and group C consisted of 20 participants aged 75 and older (5 males and 15 females, mean age 81.6 years). Inclusion criteria included being able to walk independently and follow the measurer’s instructions. Exclusion criteria comprised inability to follow the measurer’s instructions, dysphagia diagnosis, and serious systemic disease preventing completion of the measurement. The data collected in the survey were age, gender, hyoid bone position and swallowing function assessment.

Hyoid bone position

Lateral cephalometric radiographs (Veraviewepocs X550 2DB, Morita, Kyoto, Japan) were assessed to determine hyoid bone position. During radiography, subjects were instructed to stand with the Frankfurt plane parallel to the floor, ear rods were inserted into the bilateral ear canals, and the head was fixed. Subjects were instructed to swallow saliva after occlusion in the cricopharyngeal fit position, and the images were taken three seconds after swallowing. Analysis software (Win Ceph Ver. 11; Rise, Miyagi, Japan) was used to plot the H (anterior point of the hyoid bone), Me (Menton), C3 (most inferior and anterior point on the corpus of the third cervical vertebra), and MP (mandibular plane) lines (Fig.1). A dentist trained in cephalometric analysis (Y.O.) plotted the measured points, and another skilled dentist (H.S.) confirmed the results. The position of the hyoid bone (H) was evaluated vertically and horizontally using lateral cephalometric radiographs, according to a previous study [19]. The distance from C3 to H (C3-H) was measured as the horizontal position. Vertical position was evaluated in two ways. One measured the distance of the perpendicular line from H to MP (MP-H). The other measured the distance of the perpendicular line from H to the line connecting C3 and Me (C3Me-H). Participants were divided into two groups based on hyoid bone position (H) with respect to the line connecting C3 and Me (C3Me line). The High group was defined as the group with the head side above the C3Me line, and the Low group was defined as the group with the caudal side above the C3Me line. If the hyoid bone was observed above the C3Me line, the distance was treated as a negative value.

Fig. 1 Cephalometric parameters

C3-H: Distance from third cervical vertebra to hyoid bone; MP-H: Distance from mandibular plane to hyoid bone; C3Me-H: Distance from C3-Menton point line to hyoid bone

Swallowing Function Assessment

Swallowing function was assessed using RSST and EAT-10. For the RSST, the evaluator instructed the subject to swallow as many times as possible within 30 seconds, palpated the larynx, and counted the number of swallows. RSST was administered once on each subject. EAT-10 was completed by the patients themselves.

In addition, jaw-opening force (JOF) [20,21] and tongue pressure (TP) [22,23] which are associated with swallowing function, were measured. JOF was measured using a jaw-opening sthenometer (KT2016, Livit, Tokyo, Japan) (Fig.2). The measurer placed the head cap on the subject's head, placed the chin cup of the chin attachment section on the chin, and connected the adjustment belt to the cap connection to prevent chin movement. Participants were then instructed to open their jaws as strongly as possible for the measurement. JOF was defined as the maximum of two measurements. TP was measured using a JMS TP device (JMS, Hiroshima, Japan) (Fig.2). The measurement was performed after calibration outside the oral cavity, by placing the tongue pressure probe between the tongue and palate. The rigid ring of the tongue pressure probe was lightly held with the incisors, and participants were instructed to raise their tongue with maximum force against the palate for 7 s. The maximum pressure displayed on the digital tongue pressure measurement device was recorded. TP was defined as the maximum of two measurements.

Fig. 2 Measuring instruments

(left) Frontal view of the participant wearing the jaw-opening sthenometer (KT2016, Livet Inc., Tokyo, Japan) (a) monitor (b) head-encircling belt (c) chin cap (d) head and mandible fixation belt (right)Tongue pressure-measuring instrument (JMS Co., Hiroshima, Japan)

Statistical analysis

The Kruskal–Wallis test was performed to investigate the effects of age group, followed with Bonferroni post-hoc test, and a Bonferroni correction was performed to adjust the P-values. The comparison of swallowing functions between High and Low groups was performed using the Mann-Whitney U test. The chi-square test was used to determine the significance of the gender difference. Spearman’s rank correlation coefficient in the Low group was calculated to examine the characteristics of the group with lowered hyoid bone position. To investigate the characteristics based on gender in the Low group, a Mann-Whitney U test was performed separately for each gender which were further divided based on their median RSST. SPSS (version 25.0; SPSS Inc., Chicago, IL, USA) was used for all statistical analyses, and the risk rate was set at a significance level of less than 5%.

Results

The number of participants with suspected aspiration risk based on RSST was 11 (18.3%), including two males (one in Group A and one in Group C) and nine females (one in Group A, two in Group B, and six in Group C). The number of participants with suspected aspiration risk based on EAT-10 was five (8.3%), all females (one in Group A and four in Group C).

The Kruskal-Wallis test was performed to compare the effect of age on swallowing function (RSST, EAT-10, JOF, and TP) (Table 1). The results demonstrated statistically significant differences between at least two groups in RSST (P = 0.001) and TP (P = 0.010). Post-hoc Bonferroni test was performed on RSST and TP. RSST scores were significantly different between groups A and C (P = 0.006) and between groups B and C (P = 0.002). Significant differences in TP were also observed between groups A and C (P = 0.044), and between groups B and C (P = 0.016). Additionally, the Kruskal-Wallis test was performed to compare the effect of age on hyoid bone position (C3-H, MP-H, and C3Me-H). The results demonstrated that there were no statistically significant differences between any of the groups (Table 1).

Table 2 shows a comparison of swallowing function between the High and Low groups. A total of 22 subjects were grouped into the High group (3 males and 19 females) and 38 subjects into the Low group (20 males and 18 females). There was a significant difference in JOF (P = 0.020) between the High and Low groups. Spearman's rank correlation was performed on the High and Low groups to investigate how hyoid bone position is related to swallowing function. The High group exhibited no significant correlation between hyoid bone position and swallowing function. In the Low group, C3-H correlated with JOF (r = 0.430, ρ = 0.007) and C3Me-H correlated with EAT-10 (r = 0.327, ρ = 0.045) (Table 3).

The Low group were divided into two groups based on gender. The mean and median RSST scores for males in the Low group were 5.10 and 4.50, respectively. For females in the Low group, the mean and median RSST scores were 3.89 and 4.00, respectively. RSST scores were bipolarized around the median in males, but not in females. Therefore, the males were further divided into two groups: one with RSST median scores of 5 or more (n = 10) and the other with RSST scores of less than 5 (n = 10) (Fig.3). The results comparing the two groups are shown in Table 4. JOF (P = 0.009) was significantly higher in the RSST ≥ 5 group than in the RSST < 5 group. Female participants in the Low group were divided into two groups: one with RSST ≥ 4 and the other with RSST < 4 (Fig.3), and their swallowing functions were compared. The RSST ≥ 4 and RSST < 4 groups exhibited no significant difference in swallowing function (Table 4).

Table 1 Participant characteristics

Median (interquartile range). The Kruskal-Wallis test and Bonferroni post-hoc test; *P < 0.05, **P < 0.01. The chi-square test†

 

Table 2 Evaluation of swallowing function and hyoid bone position in the High and Low groups

		Total N = 60	High group n = 22	Low group n = 38	P
Age		69.5 (62.0-77.8)	64.5 (62.0-73.3)	72.0 (65.0-80.3)	0.100
Sex†	males	23	3	20	0.003††
	females	37	19	18
RSST		4.5 (3.0-6.0)	5.0 (2.8-6.0)	4.0 (3.0-6.0)	0.721
EAT-10		0.0 (0.0-1.0)	0.0 (0.0-1.3)	0.0 (0.0-1.0)	0.582
JOF (kgf)		6.4 (5.0-8.5)	5.6 (4.8-6.7)	7.5 (5.3-9.0)	0.020*
TP (kPa)		33.5 (26.7-40.5)	33.2 (28.0-37.6)	33.9 (26.3-41.6)	0.824
C3-H (mm)		39.9 (36.9-44.0)	38.0 (34.0-40.1)	41.9 (38.5-45.1)	0.003**
MP-H (mm)		15.2 (11.5-19.9)	9.7 (4.4-11.9)	17.6 (14.9-23.1)	<0.001**
C3Me-H (mm)		2.4 (-1.5-8.3)	-2.2 (-4.6-[-1.0])	6.3 (3.2-10.4)	<0.001**

Median (interquartile range). Mann-Whitney U test; *P < 0.05, **P < 0.01. The chi-square test; ††P < 0.01

 

Table 3 Association between swallowing function and hyoid bone position in the Low group

	Age	RSST	EAT-10	JOF	TP	C3-H	MP-H	C3Me-H
Age	1.000	-0.440**	0.194	-0.481**	-0.443**	-0.166	-0.005	0.159
RSST		1.000	0.072	0.464**	0.352*	0.067	0.196	0.126
EAT-10			1.000	0.012	-0.052	-0.020	0.058	0.327*
JOF				1.000	0.489**	0.430**	0.121	0.031
TP					1.000	0.144	0.107	-0.153
C3-H						1.000	0.268	0.309
MP-H							1.000	0.710**
C3Me-H								1.000

Spearman’s rank correlation coefficient; *P < 0.05, **P < 0.01

 

Fig. 3 (left) Repetitive Saliva Swallow Test (RSST) Score of male subjects categorized into the Low group. (right) Repetitive Saliva Swallow Test (RSST) Score of female subjects categorized into the Low group

Table 4 Swallowing function of males and females in the Low group

	Males			Females
	RSST ≥ 5	RSST < 5		RSST ≥ 4	RSST < 4
	(n = 10)	(n = 10)	P	(n = 10)	(n = 8)	P
Age	64.5 (58.8-69.8)	74.0 (64.3-83.3)	0.075	73.5 (68.0-81.0)	77.5 (73.4-80.5)	0.659
EAT-10	0.0 (0.0-1.3)	0.0 (0.0-0.5)	0.689	0.0 (0.0-1.0)	0.0 (0.0-3.0)	0.863
JOF (kgf)	10.6 (8.8-11.6)	7.2 (5.8-8.8)	0.009**	5.5 (4.9-7.0)	6.2 (4.1-7.7)	0.724
TP (kPa)	40.8 (33.9-53.5)	35.0 (31.3-40.2)	0.165	27.3 (23.3-38.8)	26.0 (24.6-38.9)	0.596
C3-H (mm)	43.3 (42.2-44.9)	46.1 (39.9-49.2)	0.280	38.4 (34.9-40.5)	39.0 (36.4-41.7)	0.659

Median (interquartile range). Mann-Whitney U test; **P < 0.01

Discussion

In this study, eleven participants had RSST scores of less than three, and five participants had EAT-10 of three or higher. Few subjects demonstrated RSST scores less than 3 and EAT-10 scores more than 2, indicating aspiration risk. Despite their ease of application in clinical settings, RSST and EAT-10 are considered only as early swallowing screening tests. Moreover, subjects who are in the pre-swallowing disorder stage of oral frailty have been assumed to be healthy. In this study, items related to swallowing function were scrutinized by focusing on position of the hyoid bone.

The effect of age on swallowing function was investigated across age groups, using RSST, EAT-10, JOF, and TP.

RSST has been reported to decrease with age [14,24]. Group C showed a significant difference compared to participants in groups A and B (Table 1). In this study, RSST was shown to decrease with aging, which is in line with previous reports.

A previous study measuring JOF reported significant differences between males in their 80s and other age groups, whereas no age-related differences were observed in females [25]. In this study, however, no significant differences were found between any of the groups, which may be attributed to the difference in the number of participants between males in their 80s and those less than 80 years of age.

TP is also known to decrease with age [23,25,26]. Utanohara et al. [23] reported that TP begins to decrease significantly from 60s in males and from 70s in females. In this study, there was a significant difference in TP between group A and group C (P = 0.044) and between group B and group C (P = 0.016), but no significant difference between group A and group B (P = 0.987) (Table 1). Similar trends were observed in this study as in previous studies.

As the aging process occurs, hyoid bone position has been reported to descend [19,27]. Kendall et al. [17] reported that older adults with dysphagia had slower hyoid bone elevation and less hyoid bone movement. However, in the present study, no significant differences were found between different age groups regarding hyoid bone position (Table 1). This finding might be because most participants in this study were relatively healthy participants who came to the University Hospital outpatient clinic without dysphagia or physical function impairment.

The subjects were divided into two groups (High and Low) based on hyoid bone position (C3Me line) [19] regardless of age groups to clarify factors that affect swallowing (Table 2). Since no correlation was found between hyoid bone position and swallowing function in the High group, the Low group was focused on. In the Low group, C3-H correlated with JOF, which was associated with the cross-sectional area of the geniohyoid muscle [28]. As the geniohyoid muscle pulls the hyoid bone forward and upward during swallowing, C3-H, which indicates the horizontal position of the hyoid bone, may be correlated with JOF. In addition, RSST correlated with JOF and TP; therefore, collinearity was possible. The RSST score is strongly correlated with swallowing video fluorography, with a cutoff value of 3 for detecting aspiration; however, no definitive value has been determined for subjects with oral frailty.

Previous studies have reported that the vertical position of hyoid bone in the male group was significantly lower than that in the female group [19]. It has also already been reported that there are gender differences in RSST [14], JOF [25], and TP [23], which are used in this study as indicators of swallowing function. In addition, gender was considered to be a factor that significantly affected the Low group, therefore a detailed analysis was conducted by dividing the Low group into males and females. In this study, since RSST scores of the Low group males were polarized around the median, the group was further subdivided into two groups based on the RSST median score of 5 (≥ 5 and < 5). Females in the Low group were unevenly distributed toward lower RSST scores compared to males and were divided into two groups based on median values: RSST ≥ 4 and RSST < 4. In the Low group males, JOF was significantly higher in the RSST ≥ 5 group than in the RSST < 5 group. This suggests that males with lowered hyoid bone position may still maintain a normal RSST score if JOF is preserved. Additionally, both JOF and TP tended to be high, suggesting that the combined effect of these factors may enhance the reserve capacity for swallowing, thus preserving swallowing function despite lowered hyoid bone position. It has been reported in the past that females are less likely to experience an age-related decline in JOF and may have a higher reserve capacity than males [25]. Among females in the Low group, TP in the RSST ≥ 4 group was higher than in the RSST < 4 group, although the difference was not statistically significant. In this study, as in previous reports, the higher reserve capacity of females than of males may have prevented a significant difference between the RSST ≥ 4 and RSST < 4 groups.

In particular, hyoid bone position tends to decline with age in males compared with females [19]. In the present study, the RSST scores of older males with lowered hyoid bone position were polarized. The RSST ≥ 5 group had a significantly higher JOF than the RSST < 5 group. These findings suggest that the opening force in older males with lowered hyoid bone position may influence decreased swallowing function.

This study evaluated the relationship between vertical hyoid bone position and swallowing function using four different swallowing assessments. Only JOF of males in the Low group showed a significant association. Nevertheless, this study has several limitations that should be considered when interpreting the results. Some potential sampling biases might exist owing to differences in male and female size and relatively healthy population studies, who were able to attend or work at University Hospital. Despite these limitations, the findings indicate that JOF affects swallowing function in older males with lowered hyoid bone position. With respect to the sample size calculation, post-hoc analysis was performed with α = 0.05, effect size as 0.88, and sample size as 60, which showed a high power of 0.90. Post-hoc analysis was performed on the sample size using free software (G*power 3.1.9.7, Heinrich Heine University, Düsseldorf, Germany). As these cross-sectional studies lack multivariate analysis, longitudinal studies are needed to clarify that JOF is a predictor of swallowing function for older males with lowered hyoid bone position.

Abbreviations

RSST: Repetitive Saliva Swallow Test; EAT-10: Eating Assessment Tool; H: anterior point of hyoid bone; Me: Menton; C3: most inferior and anterior point on the corpus of the third cervical vertebra; MP: Mandibular plane; C3-H: distance from C3 to H; MP-H: distance of the perpendicular line from H to MP; C3Me-H: distance of the perpendicular line from H to the line connecting C3 and Me; C3Me-H: line connecting C3 and Me; JOF: Jaw-opening force; TP: Tongue pressure

Ethical Statements

This study was approved by the Clinical Research Institutional Review Board of the Ethics Committee of Tokushima University Hospital (Approval No. 4257) and was conducted in compliance with the Declaration of Helsinki. The measurements were carried out after the patients were provided with sufficient explanation about the study, and their consent was obtained with a signature.

Conflicts of Interest

The authors declare no conflicts of interest.

Funding

This study was partially supported by JSPS KAKENHI (grant numbers: 20K18635).

Author Contributions

YO: investigation, data curation, formal analysis, writing - original draft, visualization; HS: conceptualization, methodology, funding acquisition, data curation and writing - review and editing; KF: conceptualization, data curation and writing - review and editing; AYPW: writing - review and editing; TI: conceptualization, writing - review and editing; KN: conceptualization, writing - review and editing and supervision. All authors reviewed and approved the final version of the manuscript.

ORCID iD

¹⁾YO: [e-mail], https://orcid.org/0009-0003-4381-9403

²⁾HS: [e-mail], https://orcid.org/0000-0002-3059-2700

¹⁾KF: [e-mail], https://orcid.org/0000-0001-6224-7867

¹⁾AYPW: [e-mail], https://orcid.org/0000-0003-4680-236X

¹⁾TI: [e-mail], https://orcid.org/0000-0003-0950-9957

¹⁾KN*: [e-mail], https://orcid.org/0000-0003-0856-6239

Acknowledgments

The authors thank the participants for all their support and contributions.

Data Availability Statements

Data generated during the current study is available from the corresponding author on reasonable request.

References

• 1.  Abellan van Kan G, Rolland Y, Bergman H, Morley JE, Kritchevsky SB, Vellas B (2008) The I.A.N.A Task Force on frailty assessment of older people in clinical practice. J Nutr Health Aging 12, 29-37. doi: 10.1007/BF02982161
• 2.  Chen CY, Gan P, How CH (2018) Approach to frailty in the elderly in primary care and the community. Singapore Med J 59, 240-245. doi: 10.11622/smedj.2018052
• 3.  Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J et al. (2001) Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci 56, 146-156. doi: 10.1093/gerona/56.3.m146
• 4.  Minakuchi S, Tsuga K, Ikebe K, Ueda T, Tamura F, Nagao K et al. (2016) 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
• 5.  Murayama H, Kobayashi E, Okamoto S, Fukaya T, Ishizaki T, Jersey L et al. (2020) National prevalence of frailty in the older Japanese population: Findings from a nationally representative survey. Arch Gerontol Geriatr 91,104220. doi: 10.1016/j.archger.2020.104220
• 6.  Iwasaki M, Motokawa K, Watanabe Y, Shirobe M, Inagaki H, Edahiro A et al. (2020) Association between oral frailty and nutritional status among community-dwelling older adults: the Takashimadaira study. J Nutr Health Aging 24,1003-1010. doi: 10.1007/s12603-020-1433-1
• 7.  Iwasaki M, Motokawa K, Watanabe Y, Shirobe M, Ohara Y, Edahiro A et al. (2022) Oral hypofunction and malnutrition among community-dwelling older adults: evidence from the Otassha study. Gerodontology 39, 17-25. doi: 10.1111/ger.12580
• 8.  Tani A, Mizutani S, Oku S, Yatsugi H, Chu T, Liu X et al. (2022) Association between oral function and physical pre-frailty in community-dwelling older people: a cross-sectional study. BMC Geriatr 22, 726. doi: 10.1186/s12877-022-03409-5
• 9.  Shirobe M, Watanabe Y, Tanaka T, Hirano H, Kikutani T, Nakajo K et al. (2022) Effect of an oral frailty measures program on community-dwelling elderly people: a cluster-randomized controlled trial. Gerontology 68, 377-386. doi: 10.1159/000516968
• 10.  Tanaka T, Takahashi K, Hirano H, Kikutani T, Watanabe Y, Ohara Y et al. (2018) Oral frailty as a risk factor for physical frailty and mortality in community-dwelling elderly. J Gerontol A Biol Sci Med Sci 73, 1661-1667. doi: 10.1093/gerona/glx225
• 11.  Feng X, Todd T, Lintzenich CR, Ding J, Carr JJ, Ge Y et al. (2013) Aging-related geniohyoid muscle atrophy is related to aspiration status in healthy older adults. J Gerontol A Biol Sci Med Sci 68, 853-860. doi: 10.1093/gerona/gls225
• 12.  Pearson WG Jr, Langmore SE, Zumwalt AC (2011) Evaluating the structural properties of suprahyoid muscles and their potential for moving the hyoid. Dysphagia 26, 345-351. doi: 10.1007/s00455-010-9315-z
• 13.  Kang BS, Oh BM, Kim IS, Chung SG, Kim SJ, Han TR (2010) Influence of aging on movement of the hyoid bone and epiglottis during normal swallowing: a motion analysis. Gerontology 56, 474-482. doi: 10.1159/000274517
• 14.  Ben-Hayoun DH, Asher I, Allon R, Gantz B, Boaron-Sharafi S, Pinhas S et al. (2024) Normative values of the repetitive saliva swallow test and clinical factors affecting the test scores in healthy adults. Dysphagia, Jun 7. doi: 10.1007/s00455-024-10702-5
• 15.  Belafsky PC, Mouadeb DA, Rees CJ, Pryor JC, Postma GN, Allen J et al. (2008) Validity and reliability of the Eating Assessment Tool (EAT-10). Ann Otol Rhinol Laryngol 117, 919-924. doi: 10.1177/000348940811701210
• 16.  Zhang PP, Yuan Y, Lu DZ, Li TT, Zhang H, Wang HY et al. (2023) Diagnostic accuracy of the eating assessment tool-10 (EAT-10) in screening dysphagia: a systematic review and meta-analysis. Dysphagia 38, 145-158. doi: 10.1007/s00455-022-10486-6
• 17.  Kendall KA, Leonard RJ (2001) Hyoid movement during swallowing in older patients with dysphagia. Arch Otolaryngol Head Neck Surg 127, 1224-1229. doi: 10.1001/archotol.127.10.1224
• 18.  Feng X, Todd T, Hu Y, Lintzenich CR, Carr JJ, Browne JD et al. (2014) Age-related changes of hyoid bone position in healthy older adults with aspiration. Laryngoscope 124, E231-E236. doi: 10.1002/lary.24453
• 19.  Matsuda Y, Ito E, Kimura Y, Araki K (2018) Hyoid bone position related to gender and aging using lateral cephalometric radiographs. Orthodontic Waves 77, 226-231. doi: 10.1016/j.odw.2018.08.002
• 20.  Hara K, Tohara H, Wada S, Iida T, Ueda K, Ansai T (2014) Jaw-opening force test to screen for dysphagia: preliminary results. Arch Phys Med Rehabil 95, 867-874. doi: 10.1016/j.apmr.2013.09.005
• 21.  Yanagida R, Hara K, Iida T, Tohara T, Tamada Y, Minakuchi S et al. (2022) Jaw-opening force as a useful index for dysphagia: a cross-sectional and multi-institutional study. Gerontology 68, 1258-1265. doi: 10.1159/000521392
• 22.  Yoshida M, Kikutani T, Tsuga K, Utanohara Y, Hayashi R, Akagawa Y (2006) Decreased tongue pressure reflects symptom of dysphagia. Dysphagia 21, 61-65. doi: 10.1007/s00455-005-9011-6
• 23.  Utanohara Y, Hayashi R, Yoshikawa M, Yoshida M, Tsuga K, Akagawa Y (2008) Standard values of maximum tongue pressure taken using newly developed disposable tongue pressure measurement device. Dysphagia 23, 286-290. doi: 10.1007/s00455-007-9142-z
• 24.  Persson E, Wårdh I, Östberg P (2019) Repetitive saliva swallowing test: norms, clinical relevance and the impact of saliva secretion. Dysphagia 34, 271-278. doi: 10.1007/s00455-018-9937-0
• 25.  Hara K, Tohara H, Kobayashi K, Yamaguchi K, Yoshimi K, Nakane A et al. (2018) Age-related declines in the swallowing muscle strength of men and women aged 20-89 years: a cross-sectional study on tongue pressure and jaw-opening force in 980 subjects. Arch Gerontol Geriatr 78, 64-70. doi: 10.1016/j.archger.2018.05.01
• 26.  Hatta K, Murotani Y, Takahashi T, Gondo Y, Kamide K, Masui Y et al. (2022) Decline of oral functions in old-old adults and their relationship with age and sex: the SONIC study. J Am Geriatr Soc 70, 541-548. doi: 10.1111/jgs.17535
• 27.  Meira Pazelli A, Shehab AA, Rames JD, Hussein SM, Bustos SS, Sears VA et al. (2024) Hyoid position and aging: a comprehensive analysis using AI-assisted segmentation of 282 computed tomography scans. Plast Reconstr Surg Glob Open 12, e6119. doi: 10.1097/GOX.0000000000006119
• 28.  Kajisa E, Tohara H, Nakane A, Wakasugi Y, Hara K, Yamaguchi K et al. (2018) The relationship between jaw-opening force and the cross-sectional area of the suprahyoid muscles in healthy elderly. J Oral Rehabil 45, 222-227. doi: 10.1111/joor.12596