CYP2R1 and chronic obstructive pulmonary disease: Finally, the additive model estimated that patients who were smokers (p = 0.017), former smokers (p < 0.001), overweight (p = 0.014), or obese (p = 0.016), and carriers of CYP2R1 rs10741657-A (p = 0.027) and CYP27B1 rs4646536-A (p = 0.020) alleles were associated with an increased risk of COPD.