KLK1 and chronic obstructive pulmonary disease: However, we also found that the KLK1 rs5516 polymorphism was strongly related to COPD risk in smoking participants, while carriers of the G/C genotype were at lower risk for COPD, based on the results obtained with the codominant (OR = 0.39, p = 0.007) and dominant (OR = 0.41, p = 0.007) models.