In addition, the conflicting results about the association of HO-1 genetic variants with COPD, neonatal jaundice, T2DM, and cancer, as well as the reduced sample size of clinical studies that have associated HO-2 polymorphisms with PD and AMD, do not enable drawing conclusions on the impact of HO genetic variants and these diseases. Here, HMOX1 is linked to chronic obstructive pulmonary disease.