We found that COPD (OR, 7.04; 95% CI, 3.81–12.99; P <0.001), low RBC count (≤3.5 × 1012/L; OR, 0.35; 95% CI, 0.16–0.46.10; P <0.001), and low serum ALB levels (≤35 U/L; OR, 0.18; 95% CI, 0.09–0.32; P <0.001) were the independent risk factors for SD according to the multivariable models (Table 3). The gene discussed is ALB; the disease is chronic obstructive pulmonary disease.