Fluid Distribution Index and Bioelectrical Impedance Analysis in Adolescents and Adults: Reference Values in People Residing in Mexico

Vollständiger Abstract

Worum geht es in dieser Arbeit?

Background: Bioelectrical impedance vector analysis (BIVA) allows assessment of body composition and fluid distribution without relying on predictive equations. However, recent evidence shows that reference values from three decades ago are outdated and population-specific references are required. No large-scale BIVA references exist for populations residing in Mexico. Objectives: (1) to establish sex-stratified BIVA tolerance ellipses in a large sample of adolescents and adults (16–60 years) from Guadalajara; (2) to characterize the distribution of the extracellular-to-total body water ratio (ECW/TBW) index and its association with phase angle (PhA); (3) to describe age-specific PhA percentile normative values; and (4) to examine the relationship between body mass index (BMI) category and BIVA parameters. Methods: Cross-sectional observational study of 5271 participants (3455 women, 1816 men; mean age 23.3 ± 6.6 years) assessed with the InBody® 720 multifrequency segmental analyzer in Guadalajara, Mexico (2017–2023). PhA, BIVA tolerance ellipses (50th, 75th, and 95th percentiles), and the extracellular water/total body water ratio (ECW/TBW) were calculated. Sex-specific mean vectors were compared using Hotelling’s T2 test and the Mahalanobis distance (D). Results: PhA was significantly higher in men (6.39 ± 0.57°) than in women (5.37 ± 0.56°; Cohen’s d = 1.81; p < 0.001). Mean BIVA vectors differed markedly by sex (Hotelling’s T2, p < 0.001; D = 2.42). The ECW/TBW ratio was higher in women (0.378 ± 0.006) than in men (0.371 ± 0.006; d = 1.13). A total of 29.8% of women fell within the high-normal band (0.381–0.390) versus 5.0% of men (p < 0.001). PhA correlated strongly and inversely with ECW/TBW in both sexes (women r = −0.85; men r = −0.86; both p < 0.001), and PhA increased across BMI categories from underweight to overweight in both sexes (one-way ANOVA, p < 0.001). The bioimpedance centroids of this cohort residing in Mexico were descriptively displaced relative to previous European and North American references; ethnic origin was not recorded, so this displacement cannot be attributed to ethnicity. Conclusions: The tolerance ellipses and PhA percentile norms presented here are device-specific and constitute a population reference for clinical nutritional assessment, monitoring of fluid distribution in university health programs, and future longitudinal studies in Latin American populations. The marked differences from existing international references highlight the need for population-specific standards to achieve a valid clinical interpretation of bioimpedance parameters in Latin American populations.