Could bioelectric impedance spectroscopy (BIS) measured appendicular intracellular water serve as a lean mass measurement in sarcopenia definitions? A pilot study.

DXA lean mass measurement for sarcopenia diagnosis is not always possible. Bioelectric impedance spectroscopy (BIS), a portable technology, is a potential alternative to DXA-measured lean mass. This pilot study explores the possibility and proposes an arbitrarily chosen potential cut-point for appendicular intracellular water corrected by height (aICW/ht2 ).

INTRODUCTION: Sarcopenia definitions often include DXA lean mass measurement. However, DXA is not always available. We explored the potential of a less-expensive mobile method, bioelectric impedance spectroscopy (BIS), to assess lean mass for sarcopenia determination. We hypothesized that BIS-measured appendicular intracellular water (aICW/ht2 ) would correlate with DXA-measured appendicular lean mass (ALM)/ht2 and with functional parameters. If so, establishing an aICW/ht2 cut-point in sarcopenia definitions may be feasible.

METHODS: Sixty-one community-dwelling women, mean age 79.9, had BIS and DXA lean mass, grip strength, gait speed, and jumping mechanography assessments. BIS aICW was calculated using limb length and intracellular water resistance. aICW/ht2 was compared to DXA-measured ALM/ht2 by linear regression. The European Working Group ALM/ht2 and an exploratory aICW/ht2 cut-point were utilized.

RESULTS: In this cohort, ALM/ht2 and aICW/ht2 were moderately correlated, R2  = 0.55, p < 0.0001. Lean mass was low in 7 and normal in 44 by BIS and DXA. Those with low aICW/ht2 had lower grip strength (p = 0.04) and jump power (p = 0.0002) than those with normal aICW/ht2 and ALM/ht2 . Subjects with low ALM/ht2 had lower jump power (p = 0.0006) but were not different in gait speed or grip strength.

CONCLUSIONS: BIS aICW is correlated with DXA-measured ALM directly, and when height adjusted. An aICW/ht2 cut-point of 6.5 L/m2 identified 70% of women with low ALM/ht2 . Women with low lean mass by DXA and BIS had poorer function measured by jump power. These pilot data support further evaluation of BIS measurement inclusion into sarcopenia definitions.