Corresponding author: Hidetaka Wakabayashi, Department of Rehabilitation Medicine, Yokohama City University Medical Center, 4-57 Urafune-chou, Minami ward, Yokohama city, Japan 232-0024, Phone: +81-45-261-5656, Fax: +81-45-253-9955, E-mail: email@example.com
J Frailty Aging 2014;3(2):97-103
Published online December 8, 2014, http://dx.doi.org/10.14283/jfa.2014.8
Presbyphagia refers to age-related changes in the swallowing mechanism in the elderly associated with a frailty in swallowing. Presbyphagia is different from dysphagia. Sarcopenic dysphagia is difficulty swallowing due to sarcopenia of generalized skeletal muscles and swallowing muscles. Age-related loss of swallowing muscle mass becomes evident in the geniohyoid muscle and tongue. Elderly subjects with both sarcopenia and dysphagia may have not only disease-related dysphagia but also sarcopenic dysphagia. In cases of aspiration pneumonia, deterioration in activity-, disease-, and nutrition-related sarcopenia of generalized skeletal muscles and swallowing muscles may develop into sarcopenic dysphagia. Assessment of sarcopenic dysphagia includes evaluation of both dysphagia and sarcopenia. The 10-item Eating Assessment Tool (EAT-10) and a water test combined with pulse oximetry are useful for dysphagia screening. Assessment of the multi-factorial causes of sarcopenia including nutritional review is important, because rehabilitation of sarcopenic dysphagia differs depending on its etiology. Consensus diagnostic criteria for sarcopenic dysphagia were proposed at the 19th Annual Meeting of the Japanese Society of Dysphagia Rehabilitation. Rehabilitation for sarcopenic dysphagia includes treatment of both dysphagia and sarcopenia. The core components of dysphagia rehabilitation are oral health care, rehabilitative techniques, and food modification. The causes of adult malnutrition may also contribute to the etiology of secondary sarcopenia and sarcopenic dysphagia. Therefore, nutrition management is indispensable for sarcopenic dysphagia rehabilitation. In cases of sarcopenia with numerous complicating causes, treatment should include pharmaceutical therapies for age-related sarcopenia and comorbid chronic diseases, resistance training, early ambulation, nutrition management, protein and amino acid supplementation, and non-smoking.
Key words: Rehabilitation, malnutrition, frailty, swallowing muscle, EAT-10.
The term presbyphagia refers to age-related changes in the swallowing mechanism in the elderly (1). Presbyphagia is characterized by frailty of swallowing. Modification of swallowing related solely to aging is called primary presbyphagia, while swallowing changes due to diseases in the elderly is called secondary presbyphagia (2). Presbyphagia represents healthy swallowing in elderly subjects (3), and not dysphagia. Although the exact prevalence of presbyphagia is unknown, the number of healthy older adults who have penetration and aspiration during assessment of normal swallowing by simultaneous manometry and flexible endoscopic evaluation was 75% and 30%, respectively (4). Another study that investigated the relationship of aspiration status with tongue and handgrip strength in healthy older adults using flexible endoscopic evaluation of swallowing showed that 37% of healthy elderly were aspirators (5). These results indicate that presbyphagia is common in healthy older adults.
The term sarcopenic dysphagia refers to difficulty swallowing due to sarcopenia of generalized skeletal muscles and swallowing muscles (6, 7). In frail elderly patients with oropharyngeal dysphagia, impaired safety of deglutition and aspirations are caused mainly by delayed closure of the laryngeal vestibule (8). Impaired efficacy and residue are related mainly to weak tongue bolus propulsion forces and slow hyoid motion (8). These impairments in frail elderly patients with oropharyngeal dysphagia may be associated with sarcopenia of the tongue and suprahyoid muscles, indicating the presence of sarcopenic dysphagia. The exact prevalence of sarcopenic dysphagia is unknown. The prevalence of sarcopenia assessed by appendicular skeletal muscle mass (in kgs) divided by squared height (in meters) has been estimated to range between 13% to 24% in adults over 60 years of age, and to more than 50% in people aged 80 or older (9). The prevalence of dysphagia has been reported to range between 11.4%−38% in community-dwelling elderly individuals (10-14), and 40%−68% in nursing home residents (15-17). These findings suggest that sarcopenia and dysphagia are common in elderly subjects. Frail elderly subjects with both sarcopenia and dysphagia may have not only disease-related dysphagia caused by conditions such as stroke, brain injury, neuromuscular diseases, head and neck cancer, and connective tissue diseases, but also sarcopenic dysphagia due to sarcopenia of generalized skeletal muscles and swallowing muscles.
Dysphagia management is regarded as an important current and future public health issue in geriatric medicine and rehabilitation medicine, because presbyphagia and dysphagia are common in the elderly, and increases the risk of related complications such as aspiration pneumonia, choking, dehydration, malnutrition, and a lower quality of life following loss of the joy of eating. The first part of this review focuses on presbyphagia and sarcopenic dysphagia, followed by a summary of sarcopenic dysphagia assessment and rehabilitation for sarcopenic dysphagia.
Presbyphagia refers to age-related changes in the swallowing mechanism. Presbyphagia may present in several ways: as a lack of muscle strength complicating bolus propulsion; diminished lingual pressure, obstructing bolus driving; halting of the bolus whilst swallowing, leading to a more difficult cleansing of residues; a decline in taste and smell that makes it more difficult to initiate swallowing; difficulty in controlling the bolus from the anticipatory phase; entry of the bolus into the lower airway; and finally, lack of teeth and wearing, or not wearing complete dentures which influences chewing (17).
Age-related changes in the generation of lingual pressure is a contributing factor to presbyphagia. Healthy older individuals have significantly reduced isometric tongue pressures compared with their younger counterparts (18). A longer duration of swallowing occurs largely before the more automatic pharyngeal phase of the swallow is initiated. Co-morbidities such as xerostomia, esophageal motility, sensory changes, sarcopenia, and medications can affect swallowing function (18). Although elderly subjects with presbyphagia do not have dysphagia, they may easily develop the condition because of diminished functional reserve.
The term sarcopenia was used by Rosenberg to describe an age-related decrease in muscle mass, and originated from the Greek words sarx (flesh) and penia (loss) (19, 20). This term was applied initially to denote loss of muscle mass. In 2010, the European Working Group on Sarcopenia in Older People described sarcopenia as a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength, associated with a risk of adverse outcomes such as physical disability, poor quality of life, and death (21). In 2011, the International Working Group on Sarcopenia defined the disease as an “age-associated loss of skeletal muscle mass and function. Sarcopenia is a complex syndrome that is associated with muscle mass loss alone or in conjunction with increased fat mass. The causes of sarcopenia are multi-factorial and can include disuse, changing endocrine function, chronic diseases, inflammation, insulin resistance, and nutritional deficiencies. While cachexia may be a component of sarcopenia, the two conditions are not the same (22).” Decreased muscle strength and physical function are now also included in the definition of sarcopenia.
The European Wording Group on Sarcopenia in Older People categorized sarcopenia into two types for use in clinical practice (21). Primary sarcopenia is considered to be age- related when no other cause is evident, other than ageing itself. Secondary sarcopenia should be considered when one or more other causes are evident, such as activity-, disease-, or nutrition-related sarcopenia. The etiology of sarcopenia in the elderly is multi-factorial and therefore it may not be possible to characterize each individual as having either primary or secondary sarcopenia (21). For example, 88%-91% of elderly inpatients with hospital-associated deconditioning and the disuse syndrome are malnourished and may experience not only activity-related sarcopenia, but also age-, nutrition-, and disease-related sarcopenia (23, 24).
Sarcopenia of swallowing muscles
Sarcopenia of swallowing muscles is characterized by their loss of mass and strength associated with generalized loss of skeletal muscle mass and strength. Swallowing muscles include the intrinsic muscle of the tongue and the mimic, masticatory, suprahyoid, infrahyoid, palatal, pharyngeal, and esophageal muscles. Age-related loss of muscle mass of intrinsic muscle of the tongue and geniohyoid muscle has been studied in the elderly.
Tamura et al. (25) evaluated thickness of the central part of the tongue in the elderly using ultrasonography and showed mid-arm muscle area and age were associated independently with tongue thickness. These results indicate that tongue muscle mass is associated with generalized skeletal muscle mass and aging. In elderly subjects with sarcopenia, age-related loss of both the intrinsic muscle mass of the tongue and generalized skeletal muscle mass can occur simultaneously.
Feng et al. (26) assessed the geniohyoid muscle in healthy older adults using computed tomography. This muscle helps elevate and stabilize the hyoid bone, thus protecting the airway. A decrease in the cross-sectional area of the geniohyoid muscle has been shown to occur with increasing age, with this area being significantly smaller in aspirators compared with non- aspirators, but only in older men. Increasing fatty infiltration in the middle and posterior portions of the geniohyoid muscle was also shown to be associated with aging. These findings suggest that geniohyoid muscle atrophy may be a component of decreased swallowing safety and aspiration in older adults with presbyphagia and sarcopenic dysphagia.
Butler et al. (5) demonstrated that lower anterior and posterior isometric and swallowing tongue strength were dependent on aspiration status in healthy, older adults. Although there was no difference in handgrip strength between aspirators and non-aspirators, there was a correlation between handgrip and posterior tongue strength (5). These results indicate that tongue strength may decrease with the advent of generalized loss of skeletal muscle strength, and may be related with aspiration in healthy, older adults.
Sarcopenic dysphagia is the condition where a subject has difficulty swallowing due to sarcopenia of the swallowing muscles and generalized skeletal muscles. The most common cause of dysphagia is stroke. In contrast, sarcopenic dysphagia is rarely diagnosed, because the concept and diagnostic criteria for the condition have not been defined. However, sarcopenic dysphagia may be common in elderly subjects with sarcopenia and dysphagia.
Kuroda et al. (6) explored the possible presence of sarcopenic dysphagia by examining the relationship between thinness and swallowing function in older Japanese adults with suspected swallowing disorders. The circumference of the mid- upper arm of the patients ranged from 11.2 to 26.2 cm (mean
19.4 ± 3.5 cm), and correlated significantly with swallowing function measured using a graded water-swallowing test. This finding suggested that swallowing impairment was related to thinness. The most likely explanation for these results is that the general reduction in lean body mass, including the swallowing muscles, is responsible for the association between mid-upper arm circumference and swallowing function, and indicates the presence of sarcopenic dysphagia (6).
One mechanism of sarcopenic dysphagia in frail, elderly subjects is an overlap between all the serious acute diseases that cause sarcopenia. Frail, elderly subjects with either age- related sarcopenia, presbyphagia, malnutrition, periodontal diseases, or chronic diseases (e.g. chronic obstructive pulmonary disease, chronic heart failure, chronic kidney disease) can eat regular or soft diets. However, the functional reserve of swallowing is limited in these frail individuals. For example, if they develop aspiration pneumonia, sarcopenia of generalized skeletal muscles and swallowing muscles rapidly deteriorate, because of activity-, nutrition-, and disease-related sarcopenia (Figure 1). Patients with aspiration pneumonia tend to be prescribed non-eating and bed rest during pneumonia treatment. Activity-related sarcopenia and disuse muscle atrophy develop during non-eating and bedridden periods, with peripheral parenteral nutrition being a common feeding route during pneumonia treatment. Nutrition-related sarcopenia may worsen during non-eating periods and peripheral parenteral nutrition, because it is difficult to satisfy energy expenditure under these conditions without oral intake and enteral nutrition. Disease-related sarcopenia may also be exacerbated by aspiration pneumonia as it is the cause of invasion and acute inflammation and results in catabolism of generalized skeletal muscles and swallowing muscles. Therefore, frail elderly subjects with presbyphagia can simultaneously experience activity-, disease-, and nutrition-related sarcopenia of generalized skeletal muscles and swallowing muscles, resulting in the development of sarcopenic dysphagia (7).
Figure 1: Aspiration pneumonia, etiology of sarcopenia, and sarcopenic dysphagia. Sarcopenic dysphagia is not only the result of aspiration pneumonia, but also an important cause of recurrent aspiration pneumonia
Assessment of sarcopenic dysphagia
Sarcopenic dysphagia assessment includes evaluation of both dysphagia and sarcopenia.
Screening for dysphagia is important, because presbyphagia and dysphagia are common in elderly subjects, with early detection preventing complications such as aspiration pneumonia, choking, dehydration, and malnutrition. Belafsky et al. (27) developed the 10-item Eating Assessment Tool (EAT-10, Table 1), a 10-item questionnaire for dysphagia screening, with each item scored from 0 to 4. The EAT-10 was designed specifically to address the clinical need for a rapidly self-administered and easily-scored questionnaire to assess the severity of dysphagia symptoms. An EAT-10 score ≥ 3 is abnormal and indicates the presence of swallowing difficulties. The EAT-10 has been confirmed to have excellent internal consistency, test-retest reproducibility, and criterion- based validity (27).
Table 1: 10-item Eating Assessment Tool. The subject is asked: “To what extent are the following scenarios problematic for you?”. Each item is scored from 0 (No problem) to 4 (Severe problem) according to the severity of the problem
In a previous study, we translated the EAT-10 into Japanese, and determined the reliability and validity of the Japanese version of the questionnaire (28). A cross-sectional study was performed in 393 frail, elderly subjects aged 65 years or older with dysphagia or suspected dysphagia. The severity of dysphagia was assessed using the Dysphagia Severity Scale, a 7-point ordinal scale consisting of 1, saliva aspiration; 2, food aspiration; 3, water aspiration; 4, occasional aspiration; 5, oral problems; 6, minimal problems; and 7, within normal limits (29). Points 1−6 indicate the presence of dysphagia, while points 1−4 represents dysphagia with aspiration. A total of 237 patients (60%) responded to the EAT-10. The Cronbach’s alpha coefficient was 0.946. The elderly subjects who could not respond to the EAT-10 were likely to have dysphagia. The sensitivity and specificity of not responding EAT-10 for dysphagia were 0.489 and 0.951, and for dysphagia with aspiration were 0.640 and 0.792, respectively. The median EAT-10 score of the 237 respondents was 1 (interquartile range: 0-9), with 101 respondents having a score ≥ 3. Our study showed there was a significant correlation between the EAT-10 score and the Dysphagia Severity Scale (r=-0.530, p<0.001). The sensitivity and specificity of the EAT-10 with a score ≥3 for dysphagia were 0.522 and 0.897, and for dysphagia with aspiration 0.758 and 0.749, respectively. EAT-10 is therefore a useful questionnaire to detect presbyphagia and dysphagia in frail elderly subjects.
Another screening method for dysphagia is bedside dysphagia tests, such as water or food swallowing tests, pulse oximetry, or cervical auscultation. A systematic review of bedside screening tests to detect dysphagia in patients with neurological disorders, showed the water test combined with pulse oximetry using coughing, choking, and voice alteration as endpoints was currently the best method (30). If the EAT-10 and bedside dysphagia screening tests are abnormal, further dysphagia assessment including observation of eating, videofluoroscopy, or videoendoscopic evaluation of swallowing is recommended. Although there are no characteristic swallowing changes in sarcopenic dysphagia, videofluoroscopy and videoendoscopic evaluation of swallowing can detect reduced laryngeal elevation, insufficient opening of the upper esophageal sphincter, pharyngeal residues in the valleculae and piriform sinus, and aspiration.
Sarcopenia assessment should include muscle mass and strength and physical performance. Muscle mass is assessed using either computed tomography, magnetic resonance imaging, dual energy X-ray absorptiometry, bioimpedance analysis, ultrasonography, or anthropometry. Muscle strength is evaluated by handgrip strength or knee flexion/extension strength, while physical performance is assessed by the Short Physical Performance Battery, usual gait speed, or timed get- up-and-go test. Sarcopenia of swallowing muscles can be evaluated by measuring the muscle mass of the geniohyoid muscle or tongue thickness, and muscle strength of lingual pressure and head lift strength. However, further research is necessary to develop methods for measuring the mass and strength of the swallowing muscles.
Assessment of the multi-factorial causes of sarcopenia is also important, because sarcopenic dysphagia rehabilitation may differ depending on the causes of the disorder. Activity- related sarcopenia is suspected in elderly subjects with either hospital-associated deconditioning, the disuse syndrome (23, 24), history of no oral intake, bed rest, or a sedentary lifestyle for some period of time. Disease-related sarcopenia should be considered in elderly patients with a past or present history of advanced organ failure (heart, lung, liver, kidney, and brain), inflammatory disease, malignancy, or endocrine disease (21). Nutrition-related sarcopenia is suspected in elderly subjects with inadequate dietary intake of energy and/or protein which may occur with malabsorption, gastrointestinal disorders, or use of medications that cause anorexia (21). In fact, nutritional assessment is necessary when evaluating sarcopenic dysphagia, because a systematic review of nursing home patients showed difficulties swallowing or chewing and poor oral intake were associated with weight loss, low BMI, and malnutrition (31). Another systematic review of the relationship between dysphagia and malnutrition following stroke, reported the overall odds of being malnourished were higher in dysphagic subjects compared with subjects with intact swallowing (odds ratio, 2.425; 95% confidence interval, 1.264-4.649, p < 0.008)(32). These results indicate that elderly patients with dysphagia often have malnutrition as a complication. Causes of adult malnutrition are classified as being associated with either acute illness or injury, chronic illness, or social and environmental circumstances (33). The causes of adult malnutrition may also be involved in the etiology of nutrition- and disease-related sarcopenia, and may contribute to the development of sarcopenic dysphagia. Therefore, nutritional assessment is indispensable for evaluating sarcopenic dysphagia.
Consensus diagnostic criteria for sarcopenic dysphagia
A symposium of “sarcopenia and dysphagia rehabilitation” was held during the 19th Annual Meeting of the Japanese Society of Dysphagia Rehabilitation (symposium chair: Ichiro Fujishima and Hidetaka Wakabayashi). Consensus diagnostic criteria for sarcopenic dysphagia were proposed at the symposium (Table 2). Sarcopenic dysphagia is diagnosed only in patients with dysphagia and generalized sarcopenia (generalized loss of skeletal muscle mass and strength). Although some imaging test studies of swallowing muscles have been reported (25, 26), there is no cut-off point for judging loss of swallowing muscle mass. Therefore, evaluating the loss of swallowing muscle mass using imaging tests and a definitive diagnosis for sarcopenic dysphagia remains relatively difficult at present. Further research is necessary to determine the cut-off points for loss of swallowing muscle mass. However, if there are no other causes of dysphagia except sarcopenia in the patient’s clinical history, dysphagia is likely to be caused by sarcopenia, with sarcopenic dysphagia being considered as the most probable diagnosis. In cases in whom the existence of dysphagia may be caused by other conditions such as stroke, brain injury, neuromuscular diseases, head and neck cancer, and connective tissue diseases, it is possible to diagnose sarcopenic dysphagia if the main cause of dysphagia is considered to be sarcopenia.
Sarcopenic dysphagia rehabilitation
Therapy for sarcopenic dysphagia includes dysphagia rehabilitation and treatment of sarcopenia.
The core components of dysphagia rehabilitation are oral health care, rehabilitative techniques, and food modification. In a systematic literature review of oral health care in frail older people, two studies showed that improvement of oral health care diminished the risk of developing aspiration pneumonia and also the risk of dying directly from aspiration pneumonia (34). Oral health care, consisting of tooth brushing after each meal, cleaning dentures once a day, and professional oral health care once a week, appeared to be the best intervention to reduce the incidence of aspiration pneumonia (34).
Table 2: Consensus diagnostic criteria for sarcopenic dysphagia
Rehabilitative technique, especially swallow muscle strength training, is an important component of dysphagia rehabilitation and presbyphagia treatment, although high quality evidence on its effectiveness is limited. A systematic review of the head lift exercise on the swallow function, reported positive effects including an increase in the anterior excursion of the larynx and anteroposterior diameter of the upper esophageal sphincter opening, associated with elimination of dysphagic symptoms (35). Lingual resistance exercise is another rehabilitative technique for patients with lingual weakness, swallowing disability due to frailty, other age-related conditions, or stroke (36, 37).
Compensatory procedures such as modification of food texture and liquid thickness are important strategies for dysphagia rehabilitation. Foods may be chopped, mashed, or puréed to compensate for chewing and swallowing difficulties, while liquids can be thickened to slow their transit through the oral and pharyngeal phases of swallowing to avoid aspiration. Because the number of levels of modification and characteristics vary within and across countries, the need for international standardized terminology and definitions for texture-modified foods and liquids for individuals with dysphagia have been emphasized (38). In Japan, texture- modified foods are now very advanced, and incorporate energy content (kcal), protein (g) and measures of hardness, adhesiveness, and cohesiveness for each food level (38). Instructions are also provided on whether the food should be served cold (15°C) or warm (45°C). Japanese clinicians also determine whether purée or jelly textures of extremely texture- modified foods are safer or easier to swallow (38).
Treatment of sarcopenia should include resistance training combined with supplements containing amino acids, because these are considered to be the most effective option (39, 40). Treatment of activity-related sarcopenia is to avoid non-eating, bed rest, and a sedentary lifestyle, and to promote early oral intake, early mobilization, and physical activity. Treatment for disease-related sarcopenia requires therapies for advanced organ failure, inflammatory disease, malignancy or endocrine disease, while therapy for nutrition-related sarcopenia involves appropriate nutrition management to increase muscle mass. The causes of adult malnutrition may also contribute to the etiology of secondary sarcopenia and sarcopenic dysphagia. Therefore, nutrition management is indispensable for sarcopenic dysphagia rehabilitation. In cases of sarcopenia complicated by age-, activity-, nutrition-, and disease-related factors, treatment should include pharmaceutical therapies for age-related symptoms and comorbid chronic diseases, resistance training, early ambulation, nutrition management, protein and amino acid supplementation, and encouragement to stop smoking cigarettes (39, 40).
Presbyphagia and sarcopenic dysphagia are important current and future public health issues, because they are common in the elderly population and can lead to aspiration pneumonia, the prevalence of which is increasing in the aged society. Although there are no intervention studies for presbyphagia and sarcopenic dysphagia, therapies for sarcopenic dysphagia including dysphagia rehabilitation, sarcopenia treatment, and nutrition management appear to be important for treating these conditions. Developing diagnostic criteria for presbyphagia and sarcopenic dysphagia is necessary for epidemiological and intervention studies. Consensus diagnostic criteria for sarcopenic dysphagia were therefore proposed at the 19th Annual Meeting of the Japanese Society of Dysphagia Rehabilitation. Further research is also required on presbyphagia and sarcopenic dysphagia, especially evaluating swallowing muscle mass and strength in elderly subjects.
This manuscript was presented at the 20th International Association of Gerontology and Geriatrics World Congress of Gerontology and Geriatrics, Seoul, June 25, 2013, and the 19th Annual Meeting of the Japanese Society of Dysphagia Rehabilitation, Okayama, September 23, 2013.
Conflict of Interest: H. Wakabayashi has received reimbursement for travel expenses from Nestlé Health Sciences.
Acknowledgements: This study was supported by a Grant-in- Aid for the Comprehensive Research on Aging and Health from the Ministry of Health, Labor, and Welfare of Japan.
1. Jahnke V. Dysphagia in the elderly. HNO 1991; 39: 442-444. [German]
2. Ginocchio D, Borghi E, Schindler A. Dysphagia assessment in the elderly.
Nutritional Therapy Metabolism 2009; 27: 9-15.
3. Humbert IA, Robbins J. Dysphagia in the elderly. Phys Med Rehabil Clin N Am 2008; 19: 853-866.
4. Butler SG, Stuart A, Markley L, Rees C. Penetration and aspiration in healthy older adults as assessed during endoscopic evaluation of swallowing. Ann Otol Rhinol Laryngol 2009; 118: 190-198.
5. Butler SG, Stuart A, Leng X, et al. The relationship of aspiration status with tongue and handgrip strength in healthy older adults. J Gerontol A Biol Sci Med Sci 2011; 66: 452-458.
6. Kuroda Y, Kuroda R. Relationship between thinness and swallowing function in Japanese older adults: implications for sarcopenic dysphagia. J Am Geriatr Soc 2012; 60: 1785-1786.
7. Wakabayashi H, Fujimoto A. Dysphagia due to sarcopenia: potential and practice of rehabilitation nutrition. 2012. Ishiyaku, Tokyo [Japanese]
8. Rofes L, Arreola V, Romea M, et al. Pathophysiology of oropharyngeal dysphagia in the frail elderly. Neurogastroenterol Motil 2010; 22: 851- 858.
9. Baumgartner RN, Koehler KM, Gallagher D, et al. Epidemiology of sarcopenia among the elderly in New Mexico. Am J Epidemiol 1998; 147: 755-763.
10. Bloem BR, Lagaay AM, van Beek W, Haan J, Roos RA, Wintzen AR. Prevalence of subjective dysphagia in community residents aged over 87. BMJ 1990; 300: 721-722.
11. Kawashima K, Motohashi Y, Fujishima I. Prevalence of dysphagia among community-dwelling elderly individuals as estimated using a questionnaire for dysphagia screening. Dysphagia 2004; 19: 266-271.
12. Roy N, Stemple J, Merrill RM, Thomas L. Dysphagia in the elderly: preliminary evidence of prevalence, risk factors, and socioemotional effects. Ann Otol Rhinol Laryngol 2007; 116: 858-865.
13. Serra-Prat M, Hinojosa G, López D, et al. Prevalence of oropharyngeal dysphagia and impaired safety and efficacy of swallow in independently living older persons. J Am Geriatr Soc 2011; 59: 186-187.
14. Holland G, Jayasekeran V, Pendleton N, Horan M, Jones M, Hamdy S. Prevalence and symptom profiling of oropharyngeal dysphagia in a community dwelling of an elderly population: a self-reporting questionnaire survey. Dis Esophagus 2011; 24: 476-480.
15. Steele CM, Greenwood C, Ens I, Robertson C, Seidman-Carlson R. Mealtime difficulties in a home for the aged: not just dysphagia. Dysphagia 1997; 12: 43-50, discussion 51.
16. Park YH, Han HR, Oh BM, et al. Prevalence and associated factors of dysphagia in nursing home residents. Geriatr Nurs 2013; 34: 212-217.
17. Nogueira D, Reis E. Swallowing disorders in nursing home residents: how can the problem be explained? Clin Interv Aging 2013; 8, 221-227.
18. Ney DM, Weiss JM, Kind AJ, Robbins J. Senescent swallowing: impact, strategies, and interventions. Nutr Clin Pract 2009; 24: 395-413.
19. Rosenberg IH. Summary comments: epidemiological and methodological problems in determining nutritional status of older persons. Am J Clin Nutr 1989; 50: 1231-1233.
20. Rosenberg IH. Sarcopenia: Origins and clinical relevance. J Nutr 1997; 127: 990S-991S.
21. Cruz-Jentoft AJ, Baeyens JP, Bauer JM, et al. Sarcopenia: European consensus on definition and diagnosis: Report of the European Working Group on Sarcopenia in Older People. Age Ageing 2010; 39: 412-423.
22. Fielding RA, Vellas B, Evans WJ, et al. Sarcopenia: an undiagnosed condition in older adults. Current consensus definition: prevalence, etiology, and consequences. International working group on sarcopenia. J Am Med Dir Assoc 2011; 12: 249-256.
23. Wakabayashi H, Sashika H. Association of nutrition status and rehabilitation outcome in the disuse syndrome: a retrospective cohort study. General Med 2011; 12: 69-74.
24. Wakabayashi H, Sashika H. Malnutrition is associated with poor rehabilitation outcome in elderly inpatients with hospital-associated deconditioning: a prospective cohort study. J Rehabil Med, J Rehabil Med 2014;46:277-82.
25. Tamura F, Kikutani T, Tohara T, Yoshida M, Yaegaki K. Tongue thickness relates to nutritional status in the elderly. Dysphagia 2012; 27: 556-561.
26. Feng X, Todd T, Lintzenich CR, et al. Aging-related geniohyoid muscle atrophy is related to aspiration status in healthy older adults. J Gerontol A Biol Sci Med Sci 2013; 68: 853-860.
27. Belafsky PC, Mouadeb DA, Rees CJ, et al. Validity and reliability of the Eating Assessment Tool (EAT-10). Ann Otol Rhinol Laryngol 2008; 117: 919-924.
28. Wakabayashi H, Kayashita J. Translation, reliability, and validity of the Japanese version of the 10-item Eating Assessment Tool (EAT-10) for the screening of dysphagia. J-JSPEN, in press [Japanese]
29. Kagaya H, Okada S, Shigeta R, et al. Dysphagia associated with unilateral vocal cord immobility after cardiovascular surgery. Am J Phys Med Rehabil 2011; 90: 901-907.
30. Bours GJ, Speyer R, Lemmens J, Limburg M, de Wit R. Bedside screening tests vs. videofluoroscopy or fibreoptic endoscopic evaluation of swallowing to detect dysphagia in patients with neurological disorders: systematic review. J Adv Nurs 2009; 65: 477-493.
31. Tamura BK, Bell CL, Masaki KH, Amella EJ. Factors associated with weight loss, low BMI, and malnutrition among nursing home patients: a systematic review of the literature. J Am Med Dir Assoc 2013; 14: 649- 655.
32. Foley NC, Martin RE, Salter KL, Teasell RW. A review of the relationship between dysphagia and malnutrition following stroke. J Rehabil Med 2009; 41: 707-713.
33. White JV, Guenter P, Jensen G, et al. Consensus statement: Academy of Nutrition and Dietetics and American Society for Parenteral and Enteral Nutrition: characteristics recommended for the identification and documentation of adult malnutrition (undernutrition). J Parenter Enteral Nutr 2012; 36: 275-283.
34. van der Maarel-Wierink CD, Vanobbergen JN, Bronkhorst EM, Schols JM, de Baat C. Oral health care and aspiration pneumonia in frail older people: a systematic literature review. Gerodontology 2013; 30: 3-9.
35. Antunes EB, Lunet N. Effects of the head lift exercise on the swallow function: a systematic review. Gerodontology 2012; 29: 247-257.
36. Robbins J, Gangnon RE, Theis SM, Kays SA, Hewitt AL, Hind JA. The effects of lingual exercise on swallowing in older adults. J Am Geriatr Soc 2005; 53: 1483-1489.
37. Robbins J, Kays SA, Gangnon RE, et al. The effects of lingual exercise in stroke patients with dysphagia. Arch Phys Med Rehabil 2007; 88: 150- 158.
38. Cichero JA, Steele CM, Duivestein JA, et al. The need for international terminology and definitions for texture-modified foods and thickened liquids used in dysphagia management: foundations of a global initiative. Curr Phys Med Rehabil Rep, Published online: DOI 10.1007/s40141-013- 0024-z
39. Wakabayashi H, Sakuma K. Nutrition, exercise, and pharmaceutical therapies for sarcopenic obesity. J Nutr Ther 2013; 2: 100-111.
40. Wakabayashi H, Sakuma K. Comprehensive approach to sarcopenia treatment. Curr Clin Pharmacol, Curr Clin Pharmacol 2014;9:171-80.