Longitudinal study on the relationship between extracellular water distribution changes and muscle mass in severe sarcopenia patients using multi-frequency bioelectrical impedance analysis combined with phase angle measurements

AIM: This study aimed to explore whether changes in extracellular water distribution and phase angle can serve as early markers of muscle loss in patients with severe sarcopenia. METHODS: A 12-month prospective study enrolled 128 severe sarcopenia patients (72 M, 56F; mean age 74.3 ± 6.8y), with regular multi-frequency bioelectrical impedance analysis (5-500 kHz) and phase angle measurement at 50 kHz. Body composition, physical function, and inflammation markers were periodically assessed. RESULTS: Of the 128 enrolled participants, 112 (87.5%) completed the study. Muscle mass decreased significantly over 12 months, with the most rapid loss occurring between months 3-6. Phase angle also declined consistently, and a drop of ≥ 0.3° over three months effectively predicted accelerated muscle loss. Changes in bioimpedance parameters appeared nearly three weeks before detectable muscle loss. The extracellular water-to-total body water ratio rose progressively and correlated strongly with muscle mass reduction. Limb regions showed more notable deterioration than the trunk. CONCLUSION: Multi-frequency bioelectrical impedance analysis combined with phase angle measurement offers a non-invasive and sensitive approach for early detection of muscle mass loss in severe sarcopenia. Shifts in electrical parameters and water distribution precede measurable muscle decline, highlighting a potential window for timely intervention.