COL4A4 and chronic obstructive pulmonary disease: Another COL4A4 rs1800517G > A polymorphism also played a protective role in non-smokers, and carriers of the minor allele (G) had a lower risk for COPD, based on the results for the allele (OR = 0.80, p = 0.023) and additive (OR = 0.80, p = 0.025) models.