Low Muscle Mass in the Internal Medicine Ward: Prevalence and Survival Implications

Low muscle mass is common in hospitalized patients. It is associated with adverse clinical outcomes. Reported prevalence varies widely due to non-universally accepted diagnostic criteria and the heterogeneity of the populations studied. Non-surgical ill patients are underrepresented in the literature.

To estimate the prevalence of low muscle index and its impact on survival in patients admitted to an internal medicine unit.

We prospectively enrolled patients with abdominal CT scans on admission to the Internal Medicine ward. We assessed muscle mass index (L3MI) at the level of the L3 lumbar vertebra. The primary outcome was to estimate the prevalence of low muscle mass on admission. Secondary outcomes were to determine the relationship of low L3MI with hospital mortality, length of stay, nosocomial infections, and hospital readmission.

One hundred and seven patients were included. The prevalence of low L3MI was 46.7%. An L3MI of 46.3 cm²/m² in men and 40.9 cm²/m² in women predicted death at one year with a sensitivity of 66% and a specificity of 78% (AUC = 0.62 [95% CI 0.38-0.86]) and 69 and 66% (AUC of 0.63 [95% IC 0.47-0.78]), respectively. In-hospital mortality, death at 60, 90, and 360 d, and hospital readmission were significantly higher in patients with low L3MI.

Almost half of the patients admitted to an internal medicine ward have low muscle mass index. The cutoff point of 40.9 cm²/m² in females and 46.3 cm²/m² in males predicts relevant clinical variables. We established the better L3MI cutoff value to predict 12-month mortality.