We also found a tendency toward increased IL-6 expression in patients with severe COPD compared with that in patients with moderate COPD among ex-smokers (Fig. 4b), and a strong positive correlation was observed between IL-6 and Sirt1 mRNA expression in currently smoking patients with severe COPD (Fig. 4c). The gene discussed is SIRT1; the disease is chronic obstructive pulmonary disease.