High agreement between lean mass assessed by dual-energy X-ray absorptiometry and bioelectrical impedance analysis across the adult lifespan

BackgroundBioelectrical impedance analysis (BIA) is considered a portable alternative to Dual-energy X-ray absorptiometry (DXA) when assessing deficient muscle mass, a major concern for older adults associated with increased risks of falls, fractures, disability, and mortality. However, several studies have demonstrated that BIA overestimates muscle mass in the older population and that estimates of muscle mass may depend on the BIA and DXA devices utilized. This study aims to describe the concordance between lean mass assessed by DXA and BIA across the adult population. MethodsThis study is based on data from the Copenhagen Sarcopenia Study, a cross-sectional study of 1116 healthy participants aged 22-92 years with complete measurements of lean mass from both DXA (iDXA, GE Lunar) and BIA (Inbody 770). Relative appendicular lean mass (ALM) was calculated by normalizing ALM to height2 to account for allometric differences in body size. ResultsFor the total cohort, linear regression models showed a strong correlation between BIA and DXA for ALM (R{superscript 2} = 0.95) and relative ALM (R{superscript 2} = 0.88). A small, yet consistent, bias of relative ALM values was observed where BIA measures were on average 0.25{+/-}0.50 kg/m2 higher compared to measurements by DXA. The bias was consistent across age groups with a mean difference in relative ALM of 0.24{+/-}0.50 kg/m2 and 0.26{+/-}0.49 kg/m2 for younger and older participants, respectively. ConclusionBIA is a reliable alternative to DXA for assessing lean mass, in both younger and older adults. The findings indicate that with simple correction equations for ALM and relative ALM, BIA can be a practical and accessible tool in clinical settings where DXA is unavailable. These equations make BIA particularly useful for diagnosing sarcopenia in a clinical setting, allowing for early detection and management regardless of age. Key messagesBioelectrical impedance analysis (BIA) is considered a portable alternative to Dual-energy X-ray absorptiometry (DXA) when assessing low muscle mass; a major concern for older adults which is associated with increased risks of falls, fractures, disability, and mortality. However, several studies have demonstrated that BIA overestimates muscle mass in the older population and estimates of muscle mass may depend on the BIA and DXA devices utilized. By applying the models of regression equations developed in this study, clinicians can improve the accuracy of BIA measurements, making BIA a practical alternative to DXA in clinical settings where DXA is not accessible. These findings are especially relevant for the early detection and management of sarcopenia in older adults, allowing for timely interventions to preserve muscle function and reduce the risk of adverse health outcomes.