After correction for confounding factors (age, gender, BMI, smoking pack years, comorbidity, and drugs) for COPD patients, we found a statistically significant correlation by linear regression analysis between the SIRT1 activity measured in PBMCs and both FEV1 and FEV1/FVC (p < 0.0001, r2 = 0.848 and p < 0.0001, r2 = 0.780, resp). Here, SIRT1 is linked to chronic obstructive pulmonary disease.