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Background Recently, social frailty has been increasingly recognized as a factor associated with adverse health outcomes, including physical disability and mortality. However, there are no studies about the importance of this factor among hemodialysis patients. Therefore, we investigated the relationship between social frailty and early physical dysfunction in this group of patients. Methods This was a two‐center cross‐sectional study. Older patients receiving hemodialysis were prospectively enrolled. Moreover, participants were evaluated for social frailty based on the definition of previous study and for physical function, peak oxygen uptake (peak VO2), ventilatory equivalent for carbon dioxide (VE/VCO2) slope and heart rate reserve. Then, they were divided into two groups based on the presence of physical frailty. Results Data collected from 158 individuals were statistically analyzed. The prevalence rate of social frailty was 59.5%. In the non‐physical frailty group, social frailty was found to be independently associated with reduced gait speed (P = 0.007), leg strength (P = 0.040) and peak VO2 (P = 0.023), but not with hand grip strength (P = 0.36). In the physical frailty group, there was no association between social frailty and physical function. Moreover, in patients without physical and social frailty, physical function was maintained at above accepted threshold levels, whereas peak VO2 (14.1 ± 3.3 mL/kg/min), VE/VCO2 slope (32.3 ± 5.5) and heart rate reserve (50.8% ± 21.7%) were substantially impaired. Conclusions Patients receiving hemodialysis can present with social frailty and exercise intolerance with cardiac dysfunction in the early phase, which may contribute to subsequent dysfunction. Geriatr Gerontol Int 2021; 21: 664–669.

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A recent study has reported that prefrontal cortex (PFC) activity during incremental exercise may be related to exercise termination on exhaustion. However, few studies have focused on motor-related areas during incremental exercise. This study investigated changes in the oxygenation of the PFC and motor-related areas using near-infrared spectroscopy during incremental exercise. Moreover, we analyzed the effect of exercise termination on changes in cortical oxygenation based on exercise intensity and respiratory metabolism. Sixteen healthy young male patients participated in this study. After a 4-min rest and 4-min warm-up period, incremental exercise was started at an incremental load corresponding to 20 W/min. Oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (THb) in the bilateral PFC, supplementary motor area, and primary motor cortex were measured. We evaluated changes in oxygenation in each cortex before and after the anaerobic threshold (AT) and respiratory compensation point to identify changes due to respiratory metabolism. O2Hb and THb increased from moderate intensity or after AT to maximal exercise, and HHb increased slowly compared to O2Hb and THb; these changes in hemoglobin levels were consistent in all cortical areas we measured. However, the increase in each hemoglobin level in the bilateral PFC during incremental exercise was faster than that in motor-related areas. Moreover, changes in cortical oxygenation in the right PFC were faster than those in the left PFC. These results suggest changes based on differences in neural activity due to the cortical area.