Relationship between phase angle and lower-extremity function in older adults: Itabashi Longitudinal Study on Aging.

Area of Science:

• Gerontology
• Biomedical Engineering
• Musculoskeletal Health

Background:

• Muscle quality assessment is crucial for sarcopenia diagnosis, shifting focus from mass to functional indicators.
• Phase angle (PhA), derived from bioelectrical impedance analysis (BIA), is an emerging marker for muscle quality.
• Appendicular skeletal muscle mass index (ASMI) is a traditional measure of muscle mass.

Purpose of the Study:

• To compare the association of PhA with lower extremity function against ASMI in community-dwelling older adults.
• To determine if PhA is a superior indicator of physical function compared to ASMI for sarcopenia assessment.

Main Methods:

• Cross-sectional analysis of the Itabashi Longitudinal Study on Aging cohort.
• Multivariate logistic regression analysis stratified by sex, adjusting for relevant covariates.
• Receiver operating characteristic (ROC) curve analysis to compare the discriminative ability of PhA and ASMI for low physical function (Short Physical Performance Battery score <10).

Main Results:

• 1464 older adults participated (mean age 76 years; 757 women).
• Higher quartiles of PhA were significantly associated with lower odds of low physical function (e.g., men's left leg OR 0.09, women's left leg OR 0.12).
• ASMI did not show a significant association with low physical function in either sex.
• PhA (legs and whole-body) demonstrated superior discrimination of low physical function compared to ASMI (P < 0.001).

Conclusions:

• Phase angle (PhA) is a more effective indicator of lower extremity physical function in older adults than ASMI.
• Incorporating PhA into BIA-based assessments may improve the detection of low physical function.
• PhA holds potential to enhance the diagnostic value of sarcopenia assessment.