BackgroundContinuous-subcutaneous insulin injection (CSII) therapy to type 2 diabetes mellitus (T2DM) patients generated short-term health benefits. Our aims were to investigate long-term health benefits of CSII monotherapy, in combination with metformin and pioglitazone, or with sitagliptin. MethodsIn this randomized clinical trial, patients were treated for around 90 days and were monitored for one year. Demographic and laboratory data were analysed using the UKPDS_OM2 program to estimate 20-year health benefits. Multiple linear regression model was used to identify factors associated with changes of each health benefit.ResultsFor the 134 treated patients, most health benefit indicators were improved significantly, except for renal failure. For example, life expectancies increased by 0.41±0.48 year and quality-adjusted life expectancy (QALE) by 0.45±0.46 year (p<0.001). Reductions in 20-year risk were: amputation by 70.6%, ulcer 66.7%, blindness 57.1%, stroke 45.5%, myocardial infarction 43.5%, all-causes of death 20.5%, ischaemic heart disease 6.7%, with heart failure < 0.1%. However, no difference in benefits was found among the three therapeutic protocols. Health benefits were lower for older patients, for females in amputation and ulcer risk, and for smokers in blindness risk. ConclusionsShort-term CSII therapy produced significant and multiple long-term health benefits (based on simulated risk analyses) to T2DM patients and benefits were modified by age, sex and smoking factors. The three therapeutic protocols produced the same benefits. Trial registration The clinical trial was registered in ClinicalTrials.gov on November 15, 2011, with the registration number: NCT01471808.