APOA1 and chronic obstructive pulmonary disease: In contrast, age (OR: 0.97; 95% CI: 0.96–0.98; P < 0.001), eosinophil count (OR: 0.66; 95% CI: 0.44–0.98; P = 0.042), lymphocyte ratio (OR: 0.97; 95% CI: 0.96–0.98; P < 0.001), and apolipoprotein A1 (OR: 0.56; 95% CI: 0.38–0.82; P = 0.003) were significantly associated with a reduced risk of severe COPD.