Agreement of wearable and standing bioimpedance devices with bioimpedance spectroscopy estimates of total body water in adults with Down syndrome.

Abstract

BACKGROUND: Wearable bioimpedance technology offers a potentially accessible method for assessing total body water (TBW), yet its agreement with laboratory-based approaches in adults with Down syndrome remains unclear. The purpose of this study was to evaluate whether a wearable bioimpedance device demonstrates agreement with laboratory-based bioelectrical impedance spectroscopy (BIS) estimates of TBW comparable to standing bioimpedance devices in adults with Down syndrome. METHODS: Sixteen adults with Down syndrome (age: 28.3 ± 9.2 yr; height: 150.9 ± 7.8 cm; body mass: 77.4 ± 20.3 kg) completed TBW assessment using BIS (reference), a wearable bioimpedance device (BIAW), and two standing multi-frequency bioimpedance analyzers (BIAST1, BIAST2). RESULTS: Repeated measures ANOVA revealed significant differences among devices (F (3,42) = 17.52, p < 0.001). Both standing devices produced lower TBW values compared with BIS (p < 0.001), whereas BIAW did not differ from BIS (p = 0.106). Lin's concordance correlation coefficients demonstrated strong agreement between BIS and all field-based devices (CCC = 0.82-0.92), with the highest concordance observed for the wearable device. Bland-Altman analyses showed systematic underestimation for standing devices (-3.12 ± 4.65 L and -2.36 ± 4.64 L), while the wearable exhibited the smallest bias (-1.07 ± 4.64 L). Mean absolute percentage error ranged from 5.5% to 8.7%, with the wearable device demonstrating the lowest relative error. CONCLUSION: These findings indicate that wearable bioimpedance technology demonstrated closer agreement with TBW estimates from BIS than standing BIA devices.

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