Effect of age and blood pressure on determination of normal fluid status in a general population using whole body and calf bioimpedance techniques

Normal fluid status (dry weight) can be identified by hydration markers established in the healthy population. The general population average could be influenced by age with its accompanying physiological changes and/or illness. The aims of this study were (1) to evaluate the effect of age and systolic blood pressure (SBP) on these markers; (2) to compare mean values of hydration markers as assessed by different bioimpedance techniques. Subjects from the general population (n = 212, males 105, 57.1% White, 31.6% Black, and 11.3% others) were studied. Body weight, height and SBP were measured. Whole body and calf bioimpedance (Hydra 4200) methods were utilized with subjects in the supine position. Calf normalized resistivity (CNR), fluid overload (FO), extracellular (ECV) and intracellular (ICV) volume measurements ECV/total body water (TBW) were calculated. Subjects were stratified by age; young (Group1): 18-35 years; middle (Group2): 36-60 years, senior (Group3): 61-80 years. Body mass index (BMI), CNR, and ECV/TBW differed significantly between age groups, and genders. ECV and FO increased with age in males. Decreased CNR (indicating relative increased fluid load) (p