Table 2

Metformin treatment effects on diabetes defined by fasting or 2-h postload glucose or by HbA1c ≥6.5%

SubgroupN%PLAC rate (cases/100 pyr)MET rate (cases/100 pyr)HR (95% CI) for MET vs. PLACSubgroup-by-MET PRD (95% CI), cases/100 pyrSubgroup-by-MET P
Diabetes defined by fasting or 2-h PG
 Overall2,155100.07.145.890.83 (0.73–0.93)−1.25 (−2.01 to −0.49)
 Age, years0.170.08
  25 to <4564229.88.195.990.73 (0.58–0.91)−2.2 (−3.72 to −0.68)
  45 to <601,09851.07.045.690.81 (0.69–0.96)−1.35 (−2.39 to −0.32)
  ≥6041519.35.936.281.04 (0.78–1.38)0.35 (−1.33 to 2.02)
 Sex0.550.46
  Men69832.47.495.850.78 (0.63–0.97)−1.64 (−3.03 to −0.26)
  Women1,45767.66.995.900.85 (0.73–0.98)−1.02 (−1.93 to −0.11)
 Race/ethnicity0.990.97
  Non-Hispanic white1,18855.16.525.340.82 (0.69–0.97)−1.18 (−2.15 to −0.22)
  African American44120.58.847.320.82 (0.64–1.06)−1.52 (−3.49 to 0.45)
  Hispanic33015.37.196.150.86 (0.63–1.17)−1.04 (−3.03 to 0.94)
  American Indian1115.26.825.940.86 (0.52–1.43)−0.89 (−4.01 to 2.24)
  Asian/South Pacific Islander853.98.375.790.72 (0.39–1.33)−2.58 (−6.72 to 1.56)
 BMI, kg/m20.250.37
  24 to <3068932.05.805.220.90 (0.72–1.13)−0.58 (−1.78 to 0.63)
  30 to <3565830.56.835.640.83 (0.66–1.03)−1.19 (−2.53 to 0.14)
  ≥3580837.58.676.770.78 (0.65–0.94)−1.9 (−3.30 to −0.50)
 FPG, mg/dL0.00040.02
  95–1091,44066.85.134.280.83 (0.71–0.98)−0.86 (−1.6 to −0.11)
  ≥11071533.214.1010.600.75 (0.62–0.90)−3.53 (−5.69 to −1.38)
 2-h PG, mg/dL0.600.37
  140–15369932.44.473.510.78 (0.62–1.00)−0.96 (−1.92 to 0)
  154–17273033.97.465.380.73 (0.59–0.90)−2.08 (−3.38 to −0.78)
  173–19972633.710.79.740.90 (0.72–1.09)−0.95 (−2.78 to 0.88)
 HbA1c, % (mmol/mol)0.260.27
  <6.0 (42)1,16862.95.574.470.81 (0.67–0.96)−1.10 (−1.96 to −0.23)
  6.0–6.4 (42–46)68837.18.266.220.76 (0.68–0.89)−2.03 (−3.48 to −0.59)
 GDM among parous women0.020.01
  No95180.36.335.950.94 (0.78–1.13)−0.39 (−1.48 to 0.71)
  Yes23319.711.16.480.59 (0.42–0.84)−4.57 (−7.48 to −1.67)
Diabetes defined by HbA1c ≥6.5%
  Overall1,833100.04.532.860.64 (0.55–0.75)−1.67 (−2.24 to −1.1)
 Age, years0.670.82
  25 to <4556430.75.163.530.68 (0.52–0.90)−1.63 (−2.8 to −0.46)
  45 to <6093651.04.292.740.65 (0.52–0.81)−1.56 (−2.32 to −0.79)
  ≥6033718.34.272.250.55 (0.37–0.82)−2.02 (−3.26 to −0.77)
 Sex0.080.06
  Men58631.95.212.670.52 (0.39–0.69)−2.53 (−3.61 to −1.46)
  Women1,25168.14.262.960.70 (0.58–0.85)−1.3 (−1.98 to −0.62)
 Race/ethnicity0.860.46
  Non-Hispanic white1,09059.33.612.310.64 (0.52–0.81)−1.31 (−1.96 to −0.66)
  African American28815.77.915.230.67 (0.48–0.95)−2.67 (−4.82 to −0.52)
  Hispanic29015.84.863.200.66 (0.45–0.97)−1.67 (−3.17 to −0.16)
  American Indian975.35.392.960.54 (0.28–1.04)−2.42 (−5.01 to 0.17)
  Asian/Pacific Islander723.95.832.300.42 (0.18–1.00)−3.53 (−6.6 to −0.46)
 BMI (kg/m2)0.340.88
  24 to <3060532.93.562.110.60 (0.44–0.81)−1.45 (−2.3 to −0.61)
  30 to <3557531.34.392.680.62 (0.46–0.82)−1.71 (−2.71 to −0.71)
  ≥3565735.85.653.880.70 (0.55–0.89)−1.77 (−2.89 to −0.65)
 FPG, mg/dL0.040.08
  95–1091,32872.33.552.180.62 (0.50–0.76)−1.37 (−1.95 to −0.8)
  ≥11050927.77.925.040.66 (0.51–0.85)−2.88 (−4.46 to −1.3)
 2-h PG, mg/dL0.910.71
  140–15361933.73.642.230.62 (0.46–0.84)−1.41 (−2.26 to −0.56)
  154–17263434.54.762.970.64 (0.49–0.83)−1.79 (−2.79 to −0.79)
  173–19958431.85.403.430.64 (0.49–0.84)−1.97 (−3.12 to −0.82)
 HbA1c, % (mmol/mol)1,16163.32.701.670.0570.001
  <6.0 (42)67236.79.535.650.61 (0.48–0.78)−1.03 (−1.55 to −0.51)
  6.0–6.4 (42–46)1,16163.32.701.670.63 (0.51–0.78)−3.88 (−5.43 to −2.32)
 GDM among parous women0.210.13
  No81880.44.142.970.73 (0.57–0.92)−1.17 (−2.01 to −0.34)
  Yes20019.65.802.970.52 (0.33–0.83)−2.82 (−4.78 to −0.87)
  • MET, metformin; PG, postload glucose; PLAC, placebo; pyr, person-years.