The overall risk of respiratory infection (a composite endpoint event of acute upper respiratory infection, influenza and pneumonia, and other acute lower respiratory infection) was comparable between treatment groups, except for the male stratum where the respiratory infection risk was assessed lower with the concomitant use of DPP-4 inhibitors as compared to metformin use in insulin-treated T2DM patients, with an adjusted odds ratio (OR) and 95% confidence interval (CI) of 0.77 and 0.61–0.98 (Table S2). Here, DPP4 is linked to respiratory system disorder.