In our study, the prevalence of dysphagia diagnosed with VFSS in fragile hip fracture patients was 76.4%, which was higher than that of previous studies. The prevalence of dysphagia in hip fracture patients was ranged between 5.3%-34% in previous studies, which greatly varied.[7, 22, 36] The prevalence of dysphagia observed in our study was approximately twice as high as in previous studies, and it is thought that the design of studies and different methods for assessment of dysphagia led to such differences. GUSS, which is a screening test for dysphagia, does not have high sensitivity and specificity for identifying airway aspiration, penetration, and dysphagia. Frank et al. reported that the sensitivity and specificity of GUSS for diagnosis of airway aspiration was 50% and 51.35%, respectively, when comparing the accuracy of GUSS results in patients with Parkinson's disease. Additionally, the sensitivity and specificity of GUSS for diagnosis of penetration/dysphagia were 72.97% and 35.71%, respectively.[37] In our study, the sensitivity and specificity of GUSS for diagnosis of dysphagia were 62% and 47%, respectively, and the accuracy was not high. In two patients (2.8%) who had a moderate risk of dysphagia with a score of 14 points on GUSS, airway aspiration was not observed, and those 8 patients with airway aspiration showed mild risk of dysphagia. In addition, there was no significant difference in GUSS score between the dysphagia and non-dysphagia groups that were classified based on VFSS results. Therefore, additional tests other than GUSS are required for groups with a high-risk dysphagia such as hip fracture patients, and among those tests, VFSS is the most standardized test. [38]
In a study by Byun et al., VFSS was performed retrospectively to assess the prevalence of dysphagia in hip fracture patients with dysphagia symptoms who drank 30ml of water as a screening test.[36] In such cases, patients with asymptomatic airway aspiration that do not have reflexes such as coughing and suffocation may not have been included in the VFSS. Moreover, it is possible that the prevalence was underestimated due to a selection bias that did not include patients with dysphagia such as pharyngeal delay and pharyngeal residue which can only be identified through a VFSS. In a study by Love et al., the prevalence of dysphagia was prospectively evaluated using clinical characteristics such as symptoms in swallowing food without imaging tests such as VFSS.[7] In such cases, evaluation is likely to vary according to the judgement of the examiner. In a study by Nagano et al., food oral intake scale (FOIS) was used to assess dysphagia.[22] FOIS is divided into 7 levels according to the level of oral food intake, and levels of 5 or less are defined as dysphagia. FOIS is a test with a relatively high reliability between examiners; however, the results may vary depending on the skill level of the evaluator, and there is a limitation in that the test measures the level of food intake through a tube or oral cavity.[39] Unlike the studies mentioned above, our study prospectively included all hip fracture patients within a certain period to eliminate selection bias, and VFSS was performed to objectively assess asymptomatic airway aspiration, pharyngeal delay, and pharyngeal residues in order to accurately assess the prevalence of dysphagia compared to previous studies.
The prevalence of dysphagia in hip fracture patients is considered to be significantly high even though most hip fracture patients are elderly. In a study by Mulheren et al., 31 elderly subjects with a mean age of 76.2 years who have no history of dysphagia and resided in a local community were compared with younger subjects using VFSS and Dysphagia Handicap Index (DHI).[40] DHI showed that 9 elderly subjects (29%) were suspected to have dysphagia; however, VFSS results showed no difference in the rate of aspiration between the two groups. In our study, the rate of airway aspiration in elderly hip fracture patients was 11.1%, and hip fracture is thought to increase the risk of airway aspiration. In particular, history of dementia was assessed as a factor associated with airway aspiration. Dementia increased dysphagia in previous studies, and airway aspiration in hip fracture patients with dementia may increase the duration of hospitalization and mortality through aspiration pneumonia. Therefore, VFSS needs to be performed for more active diagnosis of dysphagia.[3, 41, 42]
In previous studies, the prevalence of sarcopenia in hip fracture patients was high, and in our study, sarcopenia was diagnosed in 39 out of 72 patients (52.5%).[17, 18, 43]Univariate analysis in our study also showed that the rate of sarcopenia was significantly higher in the dysphagia group with 61.8% than in the non-dysphagia group. However, logistic regression analysis demonstrated that sarcopenia, SMI, and grip strength were not associated with dysphagia. Only preoperative Koval grade was associated dysphagia. Preoperative gait ability of patients is highly associated with sarcopenia, and the level of physical activity at the time of diagnosis of sarcopenia is evaluated by the gait speed. Therefore, dysphagia observed in hip fracture patients may be sarcopenic dysphagia, which is associated with the gait ability and physical activity.[22] Additionally, although there was no statistical significance, vitamin D deficiency was observed in both the dysphagia and non-dysphagia groups. Vitamin D plays various roles in the human body, affects both bone and muscle metabolism, maintain muscle strength, and prevent falls.[44]
Penetration was associated with preoperative Koval grade and history of respiratory and cerebrovascular diseases. Preoperative Koval grade and airway aspiration were not significantly associated although there is a tendency (adjusted OR 95% CI 0.98–3.06). Dementia was found to be a strong risk for dysphagia, and the dementia and cerebrovascular diseases showed stronger association with dysphagia than sarcopenia and preoperative gait ability. It is known that dementia and cerebrovascular diseases were highly associated with dysphagia,[45] and dysphagia rehabilitation is one of the important rehabilitations for patients with these conditions.
Recent studies have reported that osteoporosis and sarcopenia interact via various substances and hormones and that osteoporosis and sarcopenia are closely related by not only the mechanical load between muscles and bones, but also through endocrine cross talking.[46, 47] Thus, osteoporosis and osteopenia accompanied by sarcopenia is defined as osteosarcopenia.[48] In hip fracture patients, severe osteoporosis is often accompanied, and in our study, severe osteoporosis with a T-score of -3.5 or less was observed in all patients. If proper weight-bearing gait becomes impossible due to hip fractures, cross talking between bones and muscles might lead to aggravation of osteoporosis and sarcopenia, and this suggests that preoperative gait ability in our study could be a risk factor for dysphagia as well as sarcopenia.
The limitations of this study are as follows. First, long-term follow-ups of the patients were not performed in this study, which prevents measuring the long-term prognosis such as aspiration pneumonia and mortality. Additional studies with longer follow-up on the frequency of postoperative aspiration pneumonia and on the level of improvement after dysphagia rehabilitation in patients with dysphagia would be necessary in the future.
Second, there was no control group in this study, therefore, it was difficult to assess the impact of hip fractures on dysphagia because the incidence of dysphagia increases with aging. However, the prevalence of dysphagia observed in our study was remarkably high even compared to healthy elderly subjects in previous studies, which suggest that hip fracture might impact developing dysphagia, at least partially.
Despite those limitations, our study estimated more accurate prevalence using standard test methods of dysphagia evaluation, VFSS, and showed that that it might not be sufficient to use bedside screening test, such as GUSS, instead of VFSS to evaluate the swallowing ability in this population. In addition, our study found that preoperative gait ability, as well as the history of dementia and cerebrovascular diseases identified in previous studies, might be a risk factor for dysphagia in elderly hip fracture patients.