Fig. 4

Unadjusted Kaplan-Meier estimates of time to mortality in chronic obstructive pulmonary disease, comparing diabetic patients on metformin to nondiabetic patients (N = 3881). The mean follow-up period of the patients was 21.4 months, with 83,098 person-months at risk. Patients with chronic kidney disease stage 3b or higher were excluded due to concerns for confounding