Body composition estimated by bioelectrical impedance in the Swedish elderly. Development of population-based prediction equation and reference values of fat-free mass and body fat for 70-and 75-y olds

Objective: To develop a bioelectrical impedance (BIA) prediction equation for fat-free mass (FFMBIA) and present reference values of FFM and body fat (BF) for healthy Swedish elderly from population-based representative samples. Subjects: This study is based on 823 ( 344 males, 479 females) participants from two systematic samples of birth cohorts in Goteborg aged 70 ( cohort H70V, 201 males and 299 females) and 75 ( cohort NORA75, 143 males and 180 females). Methods: Body composition was measured with BIA (BIA-101, RJL system, Detroit) in both cohorts and was estimated by a four-compartment (4C) model from total body water (TBW) and total body potassium (TBK) in a sub-sample of the NORA75 cohort. The FFMBIA was validated against the FFM from the 4C model (FFM4C). Results: The FFMBIA correlated well with FFM4C (r = 0.95, SEE = 2.64 kg). The FFMBIA (kg) in 70-y-old males and females were 58.5 +/- 5.4 and 43.4 +/- 4.4, and for 75-y-old males and females were 56.1 +/- 4.7 and 42.5 +/- 4, respectively. The body fat in kg ( FM) among 70-y-old males and females were 25.2 +/- 8.1 and 25.7 +/- 8.4, and for 75-y-old males and females were 21.7 +/- 7.1 and 22.8 + 7.2, respectively. The percent body fat (BF%) among 70-y-old males and females were 29.5 +/- 5.8 and 36.3 +/- 6.4, and for 75-y-old males and females were 27.3 +/- 6 and 34.1 +/- 6.1, respectively. Conclusion: The FFM, FM and BF% from this study might be used as reference values for Swedish elderly aged 70 and 75 y.