APOA1 and chronic obstructive pulmonary disease: In turn, age (OR: 0.91; 95% CI: 0.90–0.92; P < 0.001), sex (OR: 0.71; 95% CI: 0.55–0.92; P = 0.010), allergic diseases (OR: 0.51; 95% CI: 0.31–0.84; P = 0.009), eosinophil count (OR: 0.42; 95% CI: 0.21–0.84; P = 0.014), lymphocyte ratio (OR: 0.93; 95% CI: 0.91–0.95; P < 0.001), and apolipoprotein A1 (OR: 0.45; 95% CI: 0.26–0.79; P = 0.005) were associated with a reduced risk of very severe COPD.