A new bia equation for determining appendicular lean mass in communitydwelling persons aged 80+

Objective: We aimed to evaluate the agreement between dual energy X-ray absorptiometry (DXA) and BIA equations to determine lean mass in the oldest old (80+), as well as their suitability to identify sarcopenia. Materials and methods: 174 well-functioning persons (mean age: 83,3 ± 3,0; mean BMI: 26,8 ± 3,5) were included. 1) Appendicular lean mass (ALM) was predicted using BIAbased equations available in literature (Kyle et al. 2003, Sergi et al. 2015, Scafoglieri et al. 2017), and compared to DXA outcomes 2) A new ALM-formula was generated suitable for this population 3) Prevalence and agreement for sarcopenia based on BIA-equations was calculated (compared to the standard reference cut-offs for proposed by EWGSOP) Results: 1) Literature-based BIA equations systematically overestimate ALM 2) The new prediction formula that we propose for the 80+ is: ALM = 0,827 + (0,19∗Impedance Index) + (2,101∗Sex) + (0,079∗Weight); R2 = 0,888; SEE = 1,450 kg. 3) BIA equations underestimate sarcopenia regardless the EWGSOP cut-off used. Sarcopenia classification based on our new BIA equation for ALM shows better agreement with DXA (k ≥ 0,454) compared to literature-based BIA equations (k < 0,368). Fig. 1 ALM index according to DXA and BIA-prediction formulas. The horizontal lines represent EWGSOP cut-offs for sarcopenia proposed by Delmonico et al. 2007 (Men < 7.25 kg/m2, Women < 5.67 kg/m2) Conclusions: Despite the high correlation between both methods, literature-based BIA equations consistently overestimate ALM compared to DXA in persons aged 80 and over. We propose a new equation for ALM, reaching higher agreement with DXA and thus improving the accuracy of BIA for this specific age group.