Association between phase angle and blood biomarkers in community-dwelling older adults: The role of BDNF and oxidative stress

Introduction: The association among important blood biomarkers with Phase angle (PhA) has not yet been specifically explored. Objective: To analyze the association between PhA and blood biomarkers, including BDNF, oxidative stress, metabolism, and vitamins, in community-dwelling older adults. Methods: The study was cross-sectional, involving 169 older adults from the community (Londrina-Brazil). The PhA was measured using bioimpedance with a single frequency. The following blood biomarkers from peripheral blood test were analyzed in all individuals after 10 hours of overnight fasting: Brain-derived neurotrophic factor (BDNF), Nitric Oxide (NO); Advanced Oxidation Protein Products (AOPP), Ferrous Oxidation in Xylenol orange (FOX); Glutathione Transferase (GSH); Total Plasma Antioxidant Potential (TRAP); Total Plasma Sulfhydryl (SH); Catalase (CAT); Superoxide Dismutase (SOD), Vitamin D and Vitamin B12. A linear regression model was developed to analyze the association between blood biomarkers and PhA, verifying values such as BDNF and FOX through assumption checks, considering Model 1 (unadjusted analysis) and Model 2 (adjusted for age and sex). Statistical significance was considered at p < 0.05. Results: 169 older adults were included (age= 70.17 ± 7.14 years; woman= 81%, PhA =5.33 ± 1.46 degree; BDNF= 1576.35 ± 812.75 pg/mL and FOX=0.71 ± 0.35 µ/L). Significant associations were observed between PhA and both BDNF (β=3.43x10^-4, p=0.04) and FOX (β = -8.01x10^-1, p=0.03) in Model 1 (R²=0.15). After adjustment for age and sex in Model 2 (R² = 0.16), the associations remained significant for BDNF (β=3.51x10^-4, p =0.04) and FOX (β= 7.60x10^-1, p=0.04). No significant associations were found between PhA and the other blood biomarkers. Conclusions: BDNF and FOX are the main blood biomarkers associated with PhA in community-dwelling older adults.