Asano Yujiro, Tsunoda Kenji, Nagata Koki, Lim Namhoon, Tsuji Taishi, Shibuya Kyohei, Okura Tomohiro
Doctoral Program in Physical Education, Health and Sport Science, Graduate School of Comprehensive Human Sciences, Degree Programs in Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan; National Institutes of Biomedical Innovation, Settsu-shi, Osaka, Japan; Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan.
Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Nutrition. 2025 May;133:112709. doi: 10.1016/j.nut.2025.112709. Epub 2025 Feb 7.
BACKGROUND & AIMS: Muscle quality, including phase angle (PhA) and extracellular to intracellular water (ECW/ICW) ratio, assessed using multi-frequency bioelectrical impedance analysis (MF-BIA) to reflect the contractile components of the muscle, muscle cell mass, and membrane condition, is associated with health outcomes. However, its association with the incidence of disabilities remains unclear. The aim of this study was to examine the association between whole-body and segmental PhA, ECW/ICW ratio, and the incidence of functional disability compared to conventional muscle mass.
A total of 858 older adults aged ≥65 years without functional disability at baseline were followed up for 12 years. Functional disabilities were identified using the database of the Japanese Long-Term Care Insurance System. Segmental muscle quality was assessed using the raw parameters of MF-BIA, including segmental PhA and the ECW/ICW resistance ratio. For comparison, the appendicular lean mass index (ALMI) and legMI were obtained using MF-BIA.
Functional disability was identified in 258 (30.1%) participants. Cox regression analysis showed that poorer leg PhA and ECW/ICW resistance ratios were significantly associated with a higher incidence of functional disability in both sexes, independent of covariates. A dose-response relationship indicated a higher risk for individuals with values below the median in the spline analysis. Conventional ALMI and legMI were not significantly associated with functional disability.
PhA and ECW/ICW ratio, especially in the leg, is a better predictor of functional disability than muscle mass. Muscle quality by BIA may be a useful biomarker for screening for future disabilities.
使用多频生物电阻抗分析（MF-BIA）评估的肌肉质量，包括相位角（PhA）和细胞外与细胞内水（ECW/ICW）比率，用于反映肌肉的收缩成分、肌肉细胞质量和膜状况，与健康结果相关。然而，其与残疾发生率的关联仍不明确。本研究的目的是探讨全身和节段性PhA、ECW/ICW比率与传统肌肉质量相比与功能残疾发生率之间的关联。
对858名年龄≥65岁、基线时无功能残疾的老年人进行了12年的随访。使用日本长期护理保险系统的数据库确定功能残疾情况。使用MF-BIA的原始参数评估节段性肌肉质量，包括节段性PhA和ECW/ICW电阻比。为了进行比较，使用MF-BIA获得了四肢瘦体重指数（ALMI）和腿部瘦体重指数（legMI）。
258名（30.1%）参与者被确定为有功能残疾。Cox回归分析表明，较差的腿部PhA和ECW/ICW电阻比与两性中较高的功能残疾发生率显著相关，且独立于协变量。剂量反应关系表明，在样条分析中，值低于中位数的个体风险更高。传统的ALMI和legMI与功能残疾无显著关联。
PhA和ECW/ICW比率，尤其是腿部的，比肌肉质量更能预测功能残疾。通过生物电阻抗分析得出的肌肉质量可能是筛查未来残疾的有用生物标志物。
