The aging population and rising rates of type 2 diabetes (T2DM) increase the prevalence of sarcopenia, a condition characterized by age-related loss of muscle mass, strength, and function. Sarcopenia is associated with increased disability, falls, fractures, and mortality, particularly in older adults with T2DM. Accurate and timely diagnosis is crucial for implementing targeted interventions like nutritional therapy and strength training. While methods like magnetic resonance imaging (MRI) and computed tomography (CT) are accurate, they are expensive and less accessible. Dual-energy X-ray absorptiometry (DXA) is a commonly used reference standard, but its cost, limited availability, and inability to measure very tall or obese individuals present limitations. Bioelectrical impedance analysis (BIA) offers a non-invasive, affordable, and portable alternative. However, the validity of BIA in older adults with T2DM, who may have altered body fluid composition due to various factors, remains uncertain. This study aimed to validate a direct segmental multi-frequency bioelectrical impedance analysis (DSMF-BIA) device (InBody 770) against DXA in older adults with T2DM, considering the influence of common therapeutic interventions.

Extensive literature highlights the increasing prevalence of sarcopenia in older adults, particularly those with T2DM. Studies using DXA as the gold standard have shown a strong association between sarcopenia and adverse health outcomes, including frailty, physical disability, sleep disorders, albuminuria, diabetic foot disease, and cardiovascular disease. DXA, while valuable, suffers from limitations in accessibility and applicability to certain body types. BIA, a more accessible and portable alternative, has shown promise in body composition assessment, but its validity specifically in older adults with T2DM warrants further investigation, especially given potential confounding factors like altered fluid balance caused by diabetes complications and medications.

This post-hoc analysis used data from the CEV-65 study, a randomized controlled trial investigating the effects of circuit resistance training, a plant-based Mediterranean diet, and empagliflozin on older adults with T2DM. Eighty-four participants (49 women, mean age 71 ± 5 years) with T2DM underwent both DSMF-BIA (InBody 770) and DXA (Lunar Prodigy) assessments at baseline and after a 10-week intervention period. The InBody 770 uses 30 bioimpedance measurements at six different frequencies across five body segments. DXA scans measured regional lean mass, total body fat, and total body fat percentage. Appendicular skeletal mass index (ASMI) was calculated. The degree of agreement between DSMF-BIA and DXA was assessed using Bland-Altman plots and intraclass correlation coefficients (ICC). Subgroup analyses were performed by gender and following the 10-week interventions.

The study found no significant difference in leg lean mass between DSMF-BIA and DXA (14.76 ± 3.62 kg vs. 15.19 ± 3.52 kg, p = 0.353). ASMI also showed no significant difference between the two methods (7.43 vs. 7.47 kg/m², p = 0.84; ICC = 0.965, p < 0.0001). Gender and the 10-week interventions did not significantly affect the agreement between DSMF-BIA and DXA. While some differences were observed in other body composition parameters (e.g., arm lean mass, fat mass), the overall agreement between DSMF-BIA and DXA was high, indicated by excellent ICC values (>0.9) for most parameters. DSMF-BIA demonstrated high specificity (93%) and negative predictive value (97%) for sarcopenia diagnosis compared to DXA.

The high agreement between DSMF-BIA and DXA in assessing muscle mass in older adults with T2DM supports the use of DSMF-BIA as a reliable and accessible alternative to DXA. The findings are consistent across genders and intervention groups, suggesting the robustness of the method. The slightly overestimation of arm LBM and % total-body fat by DSMF-BIA observed needs further investigation. The study's strengths include its relatively large sample size and prospective design, including a follow up after intervention. However, differences in other body composition components were noted, underscoring the importance of considering individual differences. This is particularly relevant considering the complexity of body composition changes in the population under consideration. Further research on larger, more diverse populations is necessary to fully understand this difference.

This study demonstrates that DSMF-BIA using the InBody 770 provides a reliable and accessible method for assessing muscle mass and diagnosing sarcopenia in older adults with T2DM. The method's high agreement with DXA across different genders and intervention groups makes it a valuable tool for clinical practice. Future research should focus on validating DSMF-BIA in larger, more diverse populations and exploring the discrepancies in other body composition parameters observed in this study.

The study's relatively small sample size in the post-intervention phase and the short duration of follow-up might limit the generalizability of the findings. The study population consisted of relatively younger older adults with T2DM and a lower prevalence of sarcopenia; results might not generalize completely to older older adults with more advanced disease or higher rate of comorbidities. The study was not specifically designed to validate DSMF-BIA against DXA, which could be considered a limitation in itself.