Table 3 Subgroup analyses of fasting blood glucose, fasting blood insulin and HbA1c stratified by previously defined study characteristics
| Â | Change in FBG | Change in FBI | Change in HbA1c | ||||||
|---|---|---|---|---|---|---|---|---|---|
Subgroup | Trials (n) | Net change (95%CI) (mg/dl) | I2 | Trials (n) | Net change (95%CI) (mg/dl) | I2 | Trials (n) | Net change (95%CI) (mg/dl) | I2 |
Type of intervention | |||||||||
 Green tea beverage | 8 | −0.37(−3.00, 2.27) | 0 | 4 | 1.28(− 0.48, 3.03) | 64 | 5 | −0.10(− 0.42, 0.22) | 55 |
 Green tea capsule | 20 | −1.63(−2.60,-0.66) | 22 | 15 | − 0.88(− 1.54, − 0.22) | 29 | 7 | − 0.06(− 0.13, 0.00) | 0 |
Duration | |||||||||
  ≥ 12 weeks | 15 | − 1.04(− 2.30,0.22) | 12 | 11 | − 0.35(− 1.48, 0.78) | 47 | 5 | − 0.19(− 0.42, 0.05) | 0 |
  < 12 weeks | 13 | − 2.09(− 3.14, − 1.03) | 4 | 8 | − 0.55(− 1.41, 0.30) | 56 | 7 | − 0.04(− 0.13, 0.05) | 25 |
Country | |||||||||
 Western | 13 | − 1.60(− 2.50, − 0.69) | 11 | 9 | − 0.88(− 1.71,-0.05) | 56 | 4 | − 0.02(− 0.13, 0.08) | 52 |
 Asian | 15 | − 1.20(− 3.30, 0.90) | 20 | 10 | 0.40(− 0.58, 1.37) | 20 | 8 | − 0.22(− 0.42, − 0.01) | 0 |
Catechins dose | |||||||||
  ≥ 500 mg/dl | 17 | −1.68(− 2.93,-0.43) | 39 | 11 | − 0.32(− 1.24, 0.60) | 58 | 9 | − 0.05(− 0.13, 0.03) | 16 |
  < 500 mg/dl | 10 | − 0.82(− 2.46,0.83) | 0 | 7 | − 0.79(− 2.31, 0.74) | 36 | 3 | − 0.32(− 0.77, 0.13) | 0 |
Caffeine | |||||||||
 With caffeine | 13 | −2.00(− 3.78, − 0.22) | 0 | 8 | 0.72(− 0.29, 1.73) | 31 | 5 | − 0.30(− 0.55, − 0.05) | 0 |
 Without caffeine | 12 | −1.25(− 2.65, 0.15) | 47 | 10 | −0.89(− 1.59, − 0.19) | 27 | 7 | − 0.04(− 0.11, 0.04) | 12 |
Study design | |||||||||
 Parallel | 25 | −1.51(− 2.49, − 0.53) | 21 | 16 | − 0.57(− 1.43, 0.28) | 53 | 11 | − 0.06(− 0.13, 0.02) | 8 |
 Crossover | 3 | −1.17(− 3.80, 1.46) | 0 | 3 | − 0.08(− 0.63, 0.46) | 0 | 1 | −0.30(− 1.15, 0.55) | NA |
Fasting blood glucose | |||||||||
 High(> 6.1 mmol/l) | 8 | −1.16(−6.22, 3.90) | 26 | 8 | 0.41(−0.75,1.57) | 35 | 6 | −0.26(− 0.52,0.01) | 0 |
 Normal (3.9–6.1 mmol/l) | 20 | −1.56(−2.41, − 0.72) | 11 | 11 | −0.83(− 1.61,-0.05) | 47 | 6 | − 0.04(− 0.12,0.04) | 26 |
Study quality | |||||||||
 High quality | 14 | −0.77(−1.78,0.24) | 0 | 9 | −0.39(−1.04,0.27) | 0 | 4 | 0.03(−0.20, 0.27) | 47 |
 Low quality | 14 | −2.44(−3.74,-1.15) | 10 | 10 | −0.27(−1.33, 0.79) | 67 | 8 | −0.08(− 0.15, − 0.01) | 0 |