KL and chronic obstructive pulmonary disease: The structural and physiological characteristics between aged lungs and COPD lungs overlap to a considerable extent; such characteristics include increases in the size of alveoli and end-expiratory lung volume without destruction to the alveolar wall.382,383 Additionally, the clinical features of premature lung aging can predict the possibility of being diagnosed with COPD in later years.383 Senescence-accelerated mice (SAM) and Klotho gene-knockout mice show phenotypes of COPD,384,385 indicating that aging accelerates the process of COPD.