INS and diabetes mellitus: Sub-population analysis (Fig. 3) revealed that metformin was protective in DM patients < 45 years (aHR: 0.30 [0.11–0.83]), those ≥65 years (aHR: 0.46 [0.30–0.73]), males (aHR: 0.60 [0.42–0.86]), those having an aDCSI score ≥ 3 (aHR: 0.38 [0.23–0.63]), type 2 DM patients (aHR: 0.70 [0.52–0.94]), those using insulin (aHR: 0.48 [0.32–0.73]), and those using other OHAs (aHR: 0.65 [0.48–0.87]).