Abstract Disclosure: A. Fremaint: None. G. Jung: None. E. Yu: None. M. Bouxsein: None. Introduction: Recent studies indicate that individuals with Type 1 diabetes mellitus (T1D) develop skeletal muscle health impairments which might contribute to falls and explain their high fracture risk. A novel handheld Electrical Impedance Myography (EIM) device (mScan model 1301, Myolex) has been developed to assess muscle quality by calculating tissue impedance. We hypothesized that mScan could identify individuals with worse strength and body composition outcomes among older adults with and without T1D. Methods: We studied participants of the T1D Bone Health Connection (BEACON) Study who were aged 50+ and who had undergone EIM testing (n=63 T1D, n=50 non-diabetic controls). We analyzed EIM-derived phase angle [Phase = arctan(reactance/resistance)] at 100 kHz in 3 upper extremity muscles (biceps brachii, lateral deltoid, and wrist extensors), where lower phase values indicate poorer muscle quality. Correlations of EIM data were performed with grip strength measured by a handheld dynamometer and appendicular lean mass/height2 (ALM/ht2) and visceral adipose tissue (VAT) from whole-body DXA scans. Pearson’s correlations were used for all statistical analyses. Results: Mean age (63±7 years), sex (54% female), and BMI (26.5 kg/m2) were similar between T1D and control groups. Adults with T1D had a nonsignificant trend towards lower muscle quality at the biceps brachii than controls (8.9±5.4 vs 10.9 ±6.0 degrees, p=0.078). There were no differences between groups in phase angle for lateral deltoid nor wrist extensors. Higher muscle quality at the biceps brachii was associated with higher grip strength (r=0.28, p=0.005) in the full cohort as well as in the T1D group (r=0.40, p <0.001). In the full cohort, greater VAT was associated with lower muscle health at the biceps brachii (r = -0.34, p=0.003) and lateral deltoid (r = -0.23, p<0.014), with similar patterns in both T1D and controls. There were no correlations of muscle quality with ALM/ht2. Conclusion: Our data suggest that mScan holds promise for detection of skeletal muscle health impairments in older adults, including those with T1D, potentially aiding in the diagnosis and prevention of related falls and fractures. Further research is required to investigate the association between VAT and muscle health and to validate the effectiveness of mScan in T1D and other populations. Presentation: 6/3/2024