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.

Muscle mass decreased significantly over 12 months, with the most rapid loss occurring between months 3-6.

• 128 severe sarcopenia patients were enrolled (72 male, 56 female; mean age 74.3 ± 6.8 years)
• 112 of 128 enrolled participants (87.5%) completed the 12-month prospective study
• The period of most rapid muscle loss was identified as months 3-6 of the study period
• Body composition was periodically assessed using multi-frequency bioelectrical impedance analysis at 5-500 kHz

Phase angle declined consistently over the study period, and a drop of ≥ 0.3° over three months effectively predicted accelerated muscle loss.

• Phase angle was measured at 50 kHz using multi-frequency bioelectrical impedance analysis
• A threshold decline of ≥ 0.3° over a three-month period was identified as predictive of accelerated muscle loss
• Phase angle decline was consistent across the 12-month observation period

Changes in bioimpedance parameters appeared nearly three weeks before detectable muscle loss.

• The lead time of approximately three weeks represents a potential window for timely intervention
• Bioimpedance parameters assessed included phase angle and extracellular water-to-total body water ratio
• This temporal precedence was identified using multi-frequency bioelectrical impedance analysis combined with phase angle measurement

The extracellular water-to-total body water ratio rose progressively and correlated strongly with muscle mass reduction.

• The extracellular water-to-total body water ratio increased progressively over the 12-month study period
• A strong correlation was found between rising extracellular water-to-total body water ratio and muscle mass reduction
• Physical function and inflammation markers were also periodically assessed alongside body composition measures

Limb regions showed more notable deterioration in bioimpedance parameters than the trunk.

• Regional differences in deterioration were detected using multi-frequency bioelectrical impedance analysis
• Limb regions demonstrated greater changes in electrical parameters and water distribution compared to the trunk
• Multi-frequency bioelectrical impedance was performed across the range of 5-500 kHz to allow regional body composition assessment