Comorbidity Burden Is Associated with Claims-Based Muscle Wasting and Atrophy Suggestive of Possible Sarcopenia in...

Background/Objectives: Possible sarcopenia has been proposed as an early clinical category for identifying individuals at risk of adverse muscle-related outcomes before full diagnostic evaluation. This study examined whether comorbidity burden is associated with possible sarcopenia more strongly than routinely available clinical and laboratory variables. Methods: We conducted a retrospective propensity score-matched case-control study using the Korean National Health Insurance Service database (2002-2019). Possible sarcopenia was not defined according to guideline-based muscle strength, muscle mass, or physical performance criteria. Instead, we used KCD code M62.5 as a claims-based proxy for clinically suspected muscle wasting or atrophy suggestive of possible sarcopenia. After exclusion of individuals with missing data, 1793 cases were matched 1:1 with 1793 controls according to age, sex, residential area, and insurance type. Anthropometric measures, biochemical parameters, lifestyle factors, and Charlson Comorbidity Index (CCI) scores were compared. Logistic regression and receiver operating characteristic analyses were performed to evaluate associations and discriminatory performance. Results: In the matched population, most anthropometric, biochemical, and lifestyle variables were not significantly different between groups. Fasting blood glucose and gamma-glutamyl transferase were higher in the claims-based possible sarcopenia group, but these associations were not retained in the multivariable model. The CCI score was independently associated with possible sarcopenia (odds ratio: 1.25, 95% confidence interval: 1.20-1.30; p < 0.001). In receiver operating characteristic analysis, the CCI showed the highest discriminatory ability among individual predictors (area under the curve, 0.603). The multivariable model yielded an area under the curve of 0.610. Conclusions: In administrative health data, claims-recorded muscle wasting or atrophy suggestive of possible sarcopenia was more consistently associated with multimorbidity burden than with individual routine clinical or laboratory markers. These findings support cautious, comorbidity-aware interpretation of muscle wasting/atrophy codes, but do not establish diagnostic validity for possible sarcopenia.