RETN and chronic obstructive pulmonary disease: The results of univariate analysis showed that old age [odds ratio (OR): 1.084, 95% CI: 1.028–1.144, p = 0.003], high BMI (OR: 0.844, 95% CI: 0.752–0.948, p = 0.004), high FEV1/FVC (OR: 0.957, 95% CI: 0.920–0.995, p = 0.028), and resistin (OR: 5.147, 95% CI: 3.934–11.584, p < 0.001) were associated with sarcopenia in patients with COPD.