Abstract Rationale As the global population ages, identifying risk factors for age-related diseases, such as COPD, is crucial for public health. Mosaic loss of Y chromosome (mLOY) in blood cells is an age-related somatic mosaicism event, but its relationship with pulmonary health remains undercharacterized. Objectives To examine the association between mLOY and pulmonary outcomes in men. Methods Leveraging mLOY assessment (cell fraction ≥ 5%) in over 12,000 men, including 5,097 from the COPDGene