In our study, the prevalence of discharge dynapenia was as high as 68.4% in patients with subacute stroke even though they initially had normal skeletal muscle mass. After adjusting for all potential covariates, older age, high stroke severity, and initial tube feeding were independently associated with a high likelihood of dynapenia at discharge. Meanwhile, high initial nonhemiplegic CC was significantly associated with a lower likelihood of dynapenia at discharge. To the best of our knowledge, this is the first study to identify related variables for dynapenia discharge in hospitalized patients with acute stroke.
The most striking finding of our study is that the enteral feeding via nasogastric tubes after acute stroke was the most significantly associated factor with dynapenia at discharge. This finding is consistent with a recent study which revealed that dysphagia was the most correlated risk factor with stroke-related sarcopenia in hospitalized patients receiving rehabilitation [11]. Post-stroke dysphagia is strongly associated with initial stroke severity [18]. Furthermore, poor oral health and function were associated with reduced muscle strength in post-acute stroke patients even after fully adjusting for sex, age, stroke severity, activities of daily living, cognitive level, nutritional status, comorbidities, and time from stroke onset [19]. Decreased muscle strength may occur due to infections causing muscle catabolism such as aspiration pneumonia associated with tube feeding. However, tube feeding did not seem to cause malnutrition because there was no difference in the GNRI scores between the two groups and we routinely performed nutrition evaluation and management during rehabilitation treatment.
Our study demonstrated that a higher initial NIHSS score was significantly associated with the presence of dynapenia at discharge. In accordance with our study, a prospective multinational hospital-based study revealed that the baseline NIHSS score was an excellent predictor of post-stroke functional outcomes [20]. A possible explanation for this association might be that the higher the severity of stroke, the higher the likelihood of having physical disability, which can eventually lead to a decrease in contractile capacity [21]. As patients with severe stroke are more likely to have dynapenia, further research is needed on causative factors that affect the loss of muscle strength even in the nonhemiplegic side, such as malnutrition and inflammation, as well as physical disability. It is hypothesized that neurological factors, such as insufficiency in neural activation, and muscular factors, such as an overall reduction in muscle quantity due to muscle fiber atrophy with infiltration of adipocytes, will contribute together in the development of dynapenia [3, 22].
There was an inverse association between initial nonhemipelgic CC and dynapenia at discharge. This association between CC and dynapenia indicates that high CC may have a protective role for dynapenia in patients with acute stroke. The differences in SMI and CC without that of GNRI scores between dynapenia and no dynapenia groups suggest that CC reflected the SMM more than the nutritional state. Therefore, CC may be used as an anthropometric parameter as well as a nutritional index for patients with acute stroke when the diagnostic instruments for measuring muscle mass or strength are not available. In line with our results, the ilSIRENTE study in Italy showed that HGS measures significantly improved as calf circumference increased [23]. Furthermore, high calf circumference was associated with a lower level of frailty and better functional performance in the older population [24].
Consistent with the definition of dynapenia and the results of earlier studies, the probability of having dynapenia increased with increasing age. Age has been shown to be a significant independent predictor of strength change after adjusting for muscle mass in older adults [25]. A longitudinal study investigating age-related changes in body composition, muscle strength and muscle quality found that progressive loss of strength and muscle quality commonly occurs in most older persons irrespective of change in muscle mass or body weight. Furthermore, the accumulation of fat within skeletal muscle worsens with age, regardless of changes in body weight [6]. Although previous studies have shown that alterations in muscle quantity, contractile quality and neural activation with aging may contribute to dynapenia in combination, further physiologic research is necessary to clarify the underlying mechanism of developing dynapenia with aging in patients with acute stroke [3].
Our study had some strengths and limitations. A number of studies have highlighted factors associated with stroke-related sarcopenia. However, factors related to dynapenia in patients with subacute stroke have not been studied. A strength of our study is that we documented the independent factors associated with dynapenia at discharge in older adults with subacute stroke who initially maintained normal skeletal muscle mass at admission. Knowing these factors can help to reduce the risk of subsequent dynapenia by intervention in acute stroke units and convalescent rehabilitation wards. However, our study also had some limitations. First, we used a small sample size from a single center. This may limit the generalizability of our results to other regional populations. Multicenter studies across various regions are needed. Second, there was a possibility of information bias due to missing data from the retrospective cohort. Third, the cut-off criteria for age-related loss of muscle mass and strength by the AWGS were used on stroke survivors. Because the existing diagnostic criteria has still not been determined for people with disabilities, future study is warranted to validate whether the existing diagnosis criteria needs to be adjusted. Finally, although a standardized post-stroke rehabilitation program was provided to hospitalized patients, the intensity of rehabilitation treatment could not be controlled.
In conclusion, the prevalence of discharge dynapenia is as high as 68.4% in subacute stroke patients even though they may have normal SMI at admission. Tube feeding state, higher stroke severity, decreased nonhemiplegic CC, and older age are independent risk factors for dynapenia in acute stroke patients. This information may help clinicians reduce the risk of subsequent dynapenia with appropriate intervention in acute stroke units and convalescent rehabilitation wards.