The association between two common levels of apolipoprotein and chronic obstructive pulmonary disease: A Mendelian randomized study

The association between apolipoprotein and chronic obstructive pulmonary disease (COPD) has been reported in observational studies. However, the causality of apolipoprotein on COPD remains unknown. A 2-sample Mendelian randomization (MR) analysis was performed to investigate the causal association of apolipoprotein with COPD using summary-level data. Genome-wide association studies of two apolipoproteins, apolipoprotein A-1 (ApoA-I) and apolipoprotein B, were selected as instrumental variables. COPD was included as the outcome. A significant association between ApoA-I and COPD risk was found using the inverse-variance weighted (IVW) method (odds ratio [OR]: 0.993, 95% confidence interval [CI]: 0.990–0.997, P = .0003). However, contrasting results were observed using the weighted median (OR: 0.995, 95% CI: 0.989–1.001, P = .119) and MR-Egger (OR: 0.992, 95% CI: 0.986–0.998, P = .015) methods. Since both pleiotropy and heterogeneity tests were negative (intercept = 6.032e-06, P = .948; Q = 98.996, Q -value = 0.696), and after MR-PRESSO correction, the IVW estimates can be considered acceptable. After adjusting for confounding factors, the genetic predisposition to higher levels of ApoA-I (OR = 0.993, 95% CI: 0.990–0.997, IVW P value = 0.0003) is causally associated with a reduced risk of COPD. No causal effect was found between apolipoprotein B and COPD.