COPA and chronic obstructive pulmonary disease: Using the gene-based test, our results further showed no significant association between these COPI genes and AD susceptibility (significance level 0.05), including COPA (P = 0.3186 and 0.342), COPB1 (P = 0.6095 and 0.212), COPD/PHLDB1 (P = 0.2942 and 0.325), COPZ1 (P = 0.3803 and 0.454), and COPZ2 (P = 0.08175 and 0.177) using PLINK and VEGAS, respectively.