Relationship Between Thinness and Swallowing Function in J apanese Older Adults: Implications for Sarcopenic Dysphagia

To the Editor: Older adults are likely to experience dysphagia, but the etiology of this condition is not always obvious. One possible factor that can affect decline in swallowing capabilities of elderly adults is the age-related loss of muscle mass and strength,1, 2 known as sarcopenia.3, 4 To the knowledge of the authors of this letter, no study has explored the relationship between general loss of muscle mass and swallowing function. The primary purpose of this study was to explore the possible presence of sarcopenic dysphagia by examining the relationship between thinness and swallowing function in older adults. Mid-upper arm circumference (MUAC) was used instead of body mass index (BMI) as an indicator of thinness because it is useful for bedridden individuals and is closely correlated with BMI.5, 6 Participants were individuals admitted to St. Francis Hospital (Nagasaki, Japan) between September 2010 and April 2011. The study inclusion criteria were aged 65 and older and suspected swallowing disorder. Individuals with malignant disease were excluded. There were 55 participants (18 men, 37 women) aged 68 to 102 (mean 85.4 ± 7.7). The primary reasons for admission were pneumonia (n = 28), gastrointestinal diseases (n = 11), cardiac diseases (n = 5), orthopedic diseases (n = 5), and other (n = 6). Forty of the 55 participants were reported to have dementia. MUAC was measured to determine the thinness of the subjects. Swallowing function was measured using a graded water-swallowing test (GWST), which consisted of swallowing 2, 3, and 5 mL of thin and thick water. Performance was scored using a 6-point scale, ranging from 0 (abnormal with 2 mL of thickened water) to 6 (normal with 5 mL of thin water). Physical activity was evaluated by observation of activities in the hospital ward using a 6-point rating scale ranging from 0 (completely bedridden) to 5 (able to walk without assistance). Communicative ability was measured using a 10-point observational scale7 ranging from 0 (entirely impossible) to 10 (no difficulties). Serum albumin values were also measured. MUAC levels of the patients ranged from 11.2 to 26.2 cm (mean 19.4 ± 3.5). On the basis of Japanese anthropometric reference data,8 22 of the 55 participants (40.0%) had values more than 2 SD below the mean of the corresponding normative samples, stratified according to age and sex. Serum albumin values ranged from 1.5 to 4.1 g/dL (mean 2.7 ± 0.6). GWST scores ranged from 0 to 6 (mean 4.1 ± 1.8). Physical activity assessment scores ranged from 0 to 5 (mean 1.3 ± 1.2). Communicative ability scores ranged from 0 to 10 (mean 3.9 ± 2.4). No significant differences were found between individuals with and without dementia for GWST or MUAC. As shown in Table 1, GWST was significantly correlated with MUAC (correlation coefficient (r) = 0.48, P < .001) but not with other variables. MUAC was also significantly correlated with the physical activity (r = 0.43, P = .001) and the communicative ability (r = 0.38, P = .004) assessments, and there was significant correlation between physical activity and communicative ability scores (r = 0.48, P < .001). Serum albumin values and age were not significantly correlated with any of the other variables. The overall results demonstrated that most of the participants were thin and had limited physical activity and communicative ability. GWST was significantly correlated only with MUAC. This selective correlation suggested that swallowing impairment was related to thinness and not to general frailty or presence of dementia. The most likely explanation for these results is that the general reduction in lean body mass, including the swallowing muscles, was responsible for the association between MUAC and swallowing function, suggesting the presence of sarcopenic dysphagia in Japanese older adults. The present study had the following limitations. First, MUAC cannot accurately predict degree of muscle mass loss. Second, swallowing-related muscle mass and strength were not measured. Third, the swallowing test used had not been validated. In addition, the condition of sarcopenia is difficult to define because there is no universally accepted definition.9, 10 Further studies are imperative. Conflict of Interest: The authors have no financial or any other kind of personal conflicts with this report. Author Contributions: Yoshitoshi Kuroda and Riko Kuroda were the authors of this report. Sponsor's Role: Financial support for this study was not provided.