In this cohort study, any fall accidents were observed in 42 (23.3%) maintenance dialysis patients for a one-year period. The quadriceps muscle thickness measured using ultrasonography was significantly associated with future fall injury, with the optimal cutoff values of 3.66 cm and 3.54 cm for men and women, respectively. Particularly, quadriceps muscle thickness may be more precise predictor for fall injury than the thigh circumference and handgrip strength in women dialysis patients.
Falls tend to occur in elderly people and are observed in dialysis patients with high frequency. Fall injury often lead to hospitalizations, starting the downward spiral of physical disorder that can result in long-term functional disability or death. Muscle weakness and frailty were considered the most important risk factor of falls4,10. Sarcopenia occurred more frequently in hemodialysis patients5,11. The EWGSOP gave us a common consensus about muscle mass assessment for aging. The CT scan and MRI which would be the gold standard in measuring skeletal muscle mass more precisely are widely used. On the other hand, these techniques have numerous problems including costs, limited number of facilities, time consumption, and radiation exposure, so that most dialysis units cannot carry them out routinely for a large number of subjects in general practice. Alternatively, dual-energy X-ray absorptiometry (DEXA) and bioelectrical impedance spectroscopy (BIA) are simpler inspection methods. However, DEXA remains to be problematic regarding radiation exposure and inspection equipment. Portable BIA may have calculation errors because excess fluid is miscalculated as muscle mass12.
Recently, some studies reported about the reliability of bedside ultrasound for the measurement of muscle thickness13–16. Muscle thickness measured using a sonographic technique has a high correlation with the CT scan and MRI values17. Sabatino A et al. reported the significant decrease of quadriceps femoris muscle in hemodialysis patients compared to healthy adults18. In this study, the quadriceps muscle thickness was comparable to the result of the previous study. More importantly, the quadriceps muscle thickness measured using ultrasonography was clinically verified as an independent risk factor for fall injury.
Many risk factors have been proposed for the development of fall injury in hemodialysis patients: age, diabetes, handgrip strength, antidepressant agents, and sarcopenia19,20. The association of diabetes for fall injury have already been investigated by several researchers21,22. Diabetes patients are prone to fall due to its complications such as hypoesthesia from peripheral neuropathy, loss of vision from retinopathy, orthostatic hypotension from autonomic disturbance, and hypoglycemia. In this study, diabetes is also associated with fall injury similar to those of previous studies.
Low handgrip strength can possibly cause falls or activities of daily living disability23. The handgrip strength is known to correlate with the limb muscle strength, which is available for the evaluation of muscle strength24. In this study, handgrip strength was correlated with quadriceps muscle thickness. However, median handgrip strength in women with fall injury and those women without fall injury was 16 kg and 18 kg, respectively. The difference was insignificant and hardly distinguishable. Muscle strength may not always depend on muscle mass; a study showed the association between muscle strength and muscle mass is not a straight line25. Additionally, the association of thigh circumference with fall injury as even easier parameter was investigated. However, the relationship was lesser in women because thigh circumference may include the other component except muscle mass.
Previous studies have confirmed that sarcopenia can lead to falls, disability, hospital admission, long-term care placement, poorer quality of life, and increased mortality rate24,26. Sarcopenia patients were over three times more likely to fall relative to non-sarcopenia patients27. Japan is one of the most rapidly aging countries in the world. Moreover, hemodialysis patients are generally considered as a high-risk group for sarcopenia due to inflammation, malnutrition by dietary therapy, loss of protein from dialysis membrane, low performance by complications or comorbidity, and time loss by dialysis schedules28,29. Mainly, this study aimed to assess the risk of falls affecting the prognosis of hemodialysis patients, since muscle thickness measured using ultrasonography has been confirmed to easily and accurately evaluate the risk of future fall injury.
This study had several limitations. First is the relatively few subjects enrolled in this study. The optimal cutoff values are just for reference. Second, the results were not compared with an observation of the muscle mass using CT or MRI. Third, this study did not discuss the following issues: how to improve physical performance, quality of life, and mortality from rehabilitation or nutrition management perspectives. Hence, further study is necessary considering methods of recuperation including the abovementioned issues comprehensively.