The Relationship Between Bioelectrical Impedance Analysis Parameters and Laboratory Biomarkers in an Elderly Polish Cohort: A Cross-Sectional Study

<b>Background/Objectives:</b> Assessing age-related health decline in the elderly is critical, yet standard metrics like Body Mass Index (BMI) can be misleading. Bioelectrical impedance analysis (BIA) is a popular method to assess body composition. This study evaluated the relationship between BIA-derived parameters, a comprehensive panel of laboratory biomarkers, and nutritional status in a cohort of Polish older adults. <b>Methods:</b> In a cross-sectional study of 126 elderly participants (106 women, 20 men; mean age: 72.4 years), we performed multi-frequency segmental BIA to measure fat-free mass, skeletal muscle mass, and phase angle (PA). Nutritional status was assessed using the Mini Nutritional Assessment (MNA). Venous blood samples were analyzed for a comprehensive panel of hematological, inflammatory (CRP), hormonal (leptin), and metabolic biomarkers. <b>Results:</b> The analysis characterized the body composition and biomarker profiles of the cohort. MNA-defined malnutrition risk was associated with significantly lower muscle mass and PA, and altered fluid distribution (higher extracellular-to-total body water ratio), but not with reduced fat mass. Adiposity correlated strongly with leptin and CRP. Hematological parameters were linked to lean mass, while zinc and albumin correlated with PA. Canonical analysis identified two distinct physiological axes: a dominant "adipo-hormonal" axis linking leptin to fat mass, and a secondary "metabolic-cellular integrity" axis linking zinc and iron status to Phase Angle and fluid balance. <b>Conclusions:</b> In older adults, nutritional risk is characterized by sarcopenia and fluid shifts, not low adiposity, highlighting the inadequacy of BMI. BIA parameters, especially the phase angle, may serve as promising indicators of cellular health that correlate strongly with key micronutrients, suggesting a potential role in complementary geriatric assessment.