Table 1.

Summary of diabetes prevention studies.

Study	n	Study Arms	Duration	Endpoint	Results
Lifestyle modification and diabetes prevention
The Finish Diabetes Prevention Study [18]	522	Lifestyle counselling, control group	3.2 years	Development of type 2 diabetes	Cumulative incidence of diabetes was 11% (95% CI 6-15%) in the intervention group and 23% (95% CI 17-29%) in control group
The Da Qing IGT and Diabetes Study [17]	577	Control group, diet only, exercise only, diet-plus-exercise	6 years	Development of type 2 diabetes	Cumulative incidence of diabetes at 6 years was 67.7% (95% CI 59.8-75.2) in control group compared with 43.8% (95% CI 35.5-52.3%) in diet group, 41.1% (95% CI 33.4-49.4) in exercise group and 46% (95% CI 37.3-54.7) in diet-plus- exercise group
Metformin and diabetes prevention
The Diabetes Prevention Program Research Group [19]	3234	Placebo, metformin, lifestyle modification	2.8 years	Development of type 2 diabetes	Lifestyle intervention reduced incidence by 58% (95% CI 48-66%) and metformin by 31% (95% CI 17-43%), as compared to placebo
Ramachandran et al [22]	531	Control, lifestyle modification, metformin alone, lifestyle modification and metformin	30 months	Development of type 2 diabetes	Relative risk reduction 28.5% with lifestyle modification (95% CI 20.5-37.3%, P=0.018), 26.4% with metformin (95% CI 19.1-35.1, P=0.029), 28.2% with lifestyle modification and metformin (95% CI 20.3-37.0, P=0.022)
Thiazolidinediones and diabetes prevention
The Diabetes Reduction Assessment with Ramipril and Rosiglitazone Medication [29]	5269	Rosiglitazone, placebo	3 years	Development of type 2 diabetes	Diabetes mellitus incidence in 49.5% of individuals in the rosiglitazone group (hazard ratio 0.40, 95% CI 0.35-0.46; P<0.001) and 69.7% in the placebo group (1.71, 1.57-1.87; P<0.001)
The Troglitazone in Prevention of Diabetes (TRIPOD) study [30]	133	Troglitazone, placebo	30 months	Development of type 2 diabetes	Average annual diabetes incidence rates in women who returned for follow up were 12.1% and 5.4% in placebo and troglitazone groups, respectively The hazard ratio for diabetes was 0.45% (95% CI 0.25-0.83) in the control group and 0.50 (95% CI 0.28-0.89) in the troglitazone group
The Pioglitazone in Prevention of Diabetes (PIPOD) study [31]	95	Pioglitazone, placebo	3 years	Development of type 2 diabetes	Average annual incidence rates of diabetes were 5.2% during pioglitazone treatment and 4.6% during the entire observation period, including the post-drug washout The final cumulative incidence of diabetes during treatment and post drug follow up was 17%