Table 2. Subgroup analyses of blood pressure (BP) stratified by previously defined study characteristics.
| Systolic blood pressure (SBP) | Diastolic blood pressure (DBP) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Test of heterogeneity | Test of heterogeneity | |||||||||
| Variables | No. of trials | Net change (95% CI) | P | I2,% | P | No. of trials | Net change (95% CI) | P | I2,% | P |
| BP status | ||||||||||
| Stage 1hypertension | 3 | −3.52 (−5.61, −1.43)a | 0.30 | 16.2 | 0.001 | 3 | −4.30 (−5.99, −2.60)a | 0.81 | <0.001 | <0.001 |
| −3.56 (−5.65, −1.47)b | 0.006 | −4.30 (−5.99, −2.60)b | <0.001 | |||||||
| Prehypertension | 9 | −1.57 (−2.66, −0.48)a | 0.56 | <0.001 | 0.005 | 9 | −1.33 (−2.11, −0.56)a | 0.05 | 49.3 | 0.001 |
| −1.57 (−2.66, −0.48)b | 0.005 | −1.96 (−3.53, −0.39)b | 0.012 | |||||||
| Study design | ||||||||||
| Parallel | 11 | −2.82 (−3.95, −1.69)a | 0.95 | <0.001 | <0.001 | 11 | −2.52 (−3.33, −1.70)a | 0.29 | 15.9 | <0.001 |
| −2.82 (−3.95, −1.69)b | <0.001 | −2.39 (−3.37, −1.41)b | <0.001 | |||||||
| Crossover | 2 | 0.31 (−1.54, 2.16)a | 0.97 | <0.001 | 0.743 | 2 | 0.05 (−1.33, 1.43)a | 0.04 | 76.0 | 0.942 |
| 0.31 (−1.54, 2.16)b | 0.743 | −2.20 (−8.49, 4.10)b | 0.494 | |||||||
| Type of intervention | ||||||||||
| Trials ruling out confounding effect of caffeine | 9 | −2.00 (−2.99, −1.01)a | 0.19 | 28.8 | <0.001 | 9 | −1.84 (−2.56, −1.12)a | 0.01 | 63.0 | <0.001 |
| −2.04 (−3.31, −0.77)b | 0.002 | −1.89 (−3.24, −0.54)b | 0.006 | |||||||
| Trials using green tea contained caffeine | 4 | −1.55 (−5.84, 2.75)a | 0.89 | <0.001 | 0.481 | 4 | −2.16 (−5.36, 1.05)a | 0.23 | 30.5 | 0.187 |
| −1.55 (−5.84, 2.75)b | 0.481 | −2.15 (−6.06, 1.76)b | 0.281 | |||||||
| Duration | ||||||||||
| <12 wk (low median) | 5 | −0.44 (−1.97, 1.09)a | 0.59 | <0.001 | 0.575 | 5 | −0.79 (−1.90, 0.32)a | 0.02 | 65.3 | 0.161 |
| −0.44 (−1.97, 1.09)b | 0.575 | −1.60 (−4.16, 0.96) | 0.220 | |||||||
| ≥12 wk (low median) | 8 | −2.98 (−4.21, −1.74)a | 0.91 | <0.001 | <0.001 | 8 | −2.57 (−3.48, −1.66)a | 0.29 | 17.2 | <0.001 |
| −2.98 (−4.21, −1.74)b | <0.001 | −2.43 (−3.54, −1.32)b | <0.001 | |||||||
| Green tea polyphenols dose | ||||||||||
| <582.8 mg/d (low median) | 6 | −2.87 (−4.23, −1.51)a | 0.55 | <0.001 | <0.001 | 6 | −3.19 (−4.20, −2.18)a | 0.44 | <0.001 | <0.001 |
| −2.87 (−4.23, −1.51)b | <0.001 | −3.19 (−4.20, −2.18)b | <0.001 | |||||||
| ≥582.8 mg/d (high median) | 7 | −1.08 (−2.44, 0.29)a | 0.60 | <0.001 | 0.122 | 7 | −0.60 (−1.58, 0.37)a | 0.23 | 25.9 | 0.227 |
| −1.08 (−2.44, 0.29)b | 0.122 | −0.79 (−2.11, 0.54)b | 0.244 | |||||||
| Jadad score | ||||||||||
| Low (<4) | 8 | −1.76 (−3.92, 0.40)a | 0.97 | <0.001 | 0.110 | 8 | −1.17 (−2.67, 0.32)a | 0.47 | <0.001 | 0.125 |
| −1.76 (−3.92, 0.40)b | 0.110 | −1.17 (−2.67, 0.32)b | 0.125 | |||||||
| High (≥4) | 5 | −2.03 (−3.10, −0.96)a | 0.04 | 60.7 | <0.001 | 5 | −2.04 (−2.84, −1.25)a | 0.001 | 78.1 | <0.001 |
| −2.15 (−3.94, −0.36)b | 0.019 | −2.20 (−4.06, −0.35)b | 0.020 | |||||||
aThe result was obtained from a fixed-effects model.
bThe result was obtained from a random-effects model.