Aims/hypothesis: Lifestyle modification helps in the primary prevention of diabetes in multiethnic American, Finnish and Chinese populations. In a prospective community-based study, we tested whether the progression to diabetes could be influenced by interventions in native Asian Indians with IGT who were younger, leaner and more insulin resistant than the above populations.
Methods: We randomised 531 (421 men 110 women) subjects with IGT (mean age 45.9+/-5.7 years, BMI 25.8+/-3.5 kg/m(2)) into four groups. Group 1 was the control, Group 2 was given advice on lifestyle modification (LSM), Group 3 was treated with metformin (MET) and Group 4 was given LSM plus MET. The primary outcome measure was type 2 diabetes as diagnosed using World Health Organization criteria.
Results: The median follow-up period was 30 months, and the 3-year cumulative incidences of diabetes were 55.0%, 39.3%, 40.5% and 39.5% in Groups 1-4, respectively. The relative risk reduction was 28.5% with LSM (95% CI 20.5-37.3, p=0.018), 26.4% with MET (95% CI 19.1-35.1, p=0.029) and 28.2% with LSM + MET (95% CI 20.3-37.0, p=0.022), as compared with the control group. The number needed to treat to prevent one incident case of diabetes was 6.4 for LSM, 6.9 for MET and 6.5 for LSM + MET.
Conclusions/interpretation: Progression of IGT to diabetes is high in native Asian Indians. Both LSM and MET significantly reduced the incidence of diabetes in Asian Indians with IGT; there was no added benefit from combining them.