Table 1

Characteristics of participants in metformin and placebo groups at DPP baseline (1996–1999)

Cohort for glucose-based diagnosesCohort for HbA1c-based diagnoses
Total (N = 2,155)Placebo (N = 1,082)Metformin (N = 1,073)Total (N = 1,833)Placebo (N = 922)Metformin (N = 911)
Age (yr)
 Mean ± SD50.6 ± 10.450.3 ± 10.450.9 ± 10.350.3 ± 10.350.1 ± 10.450.4 ± 10.2
 25–44642 (29.8)324 (29.9)318 (29.6)562 (30.7)283 (30.7)279 (30.6)
 45–591,098 (51.0)557 (51.5)541 (50.4)934 (51)468 (50.8)466 (51.2)
 ≥60415 (19.3)201 (18.6)214 (19.9)337 (18.4)171 (18.5)166 (18.2)
Female1,457 (67.6)747 (69.0)710 (66.2)1,249 (68.1)643 (69.7)606 (66.5)
Parous women
 No history of GDM951 (80.3)487 (80.0)464 (80.6)818 (80.4)422 (80.2)396 (80.5)
 History of GDM233 (19.7)122 (20.0)111 (19.3)200 (19.6)104 (19.8)96 (19.5)
Race/ethnicity
 Non-Hispanic white1,188 (55.1)586 (54.2)602 (56.1)1,087 (59.3)539 (58.5)548 (60.2)
 African American441 (20.4)220 (20.3)221 (20.6)287 (15.7)140 (15.2)147 (16.1)
 Hispanic330 (15.3)168 (15.5)162 (15.1)290 (15.8)151 (16.4)139 (15.3)
 American Indian111 (5.2)59 (5.5)52 (4.8)97 (5.3)50 (5.4)47 (5.2)
 Asian/Pacific Islander85 (3.9)49 (4.5)36 (3.4)72 (3.9)42 (4.6)30 (3.3)
BMI (kg/m2)
 Mean ± SD34.0 ± 6.634.1 ± 6.733.9 ± 6.633.7 ± 6.533.8 ± 6.533.6 ± 6.4
 <30689 (32.0)340 (31.4)349 (32.5)603 (32.9)300 (32.5)303 (33.3)
 30 to <35658 (30.5)315 (29.1)343 (32.0)574 (31.3)276 (29.9)298 (32.7)
 ≥35808 (37.5)427 (39.5)381 (35.5)656 (35.8)346 (37.5)310 (34)
Fasting glucose (mg/dL)
 Mean ± SD 106.6 ± 8.4106.7 ± 8.4106.5 ± 8.5105.4 ± 7.4105.6 ± 7.4105.2 ± 7.4
 95–109 1,440 (66.8)726 (67.1)714 (66.5)1,324 (72.2)663 (71.9)661 (72.6)
 110–125* 715 (33.2)356 (32.9)359 (33.5)509 (27.8)259 (28.1)250 (27.4)
2-h glucose (mg/dL)
 Mean ± SD 164.8 ± 17.2164.5 ± 17.1165.1 ± 17.2164.0 ± 16.9163.8 ± 16.9164.3 ± 17.0
 140–153 699 (32.8)360 (33.3)339 (31.6)617 (33.7)315 (34.2)302 (33.2)
 154–172 730 (34.3)374 (34.6)356 (33.2)633 (34.5)328 (35.6)305 (33.5)
 173–199 726 (33.7)348 (32.2)378 (35.2)583 (31.8)279 (30.3)304 (33.4)
HbA1c
 Mean ± SD (%)5.9 ± 0.505.9 ± 0.515.9 ± 0.505.8 ± 0.395.8 ± 0.45.8 ± 0.4
 <6% (42 mmol/mol)1,168 (54.3)578 (53.6)590 (55.1)1,161 (63.3)576 (62.5)585 (64.2)
 6–6.4% (42–46 mmol/mL) 982 (45.7)501 (46.4)533 (49.7)672 (36.7)346 (37.5)326 (35.8)
  • Data are n (%) unless otherwise indicated. yr, years.

  • *Thirty-eight participants who were recruited prior to the American Diabetes Association change in diagnostic criteria (9) had fasting glucose levels between 125 and 139 mg/dL at baseline.