Table 3. Results of subgroup analyses according to study or participant characteristics.
| No. of studies | WMD (95% CI) | P within group | P between group* | Pheterogeneity | I2, % | No. of studies | WMD (95% CI) | P within group | P between group* | Pheterogeneity | I2, % | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SBP | DBP | |||||||||||
| Education | ||||||||||||
| Total | 20 | -2.75 (-4.30, -1.19) | 0.001 | <0.001 | 94.8 | 20 | -2.11 (-3.17, -1.06) | <0.001 | <0.001 | 92.6 | ||
| Quality | 0.40 | 0.41 | ||||||||||
| heigh | 7 | -1.72 (-2.51, -0.92) | <0.001 | 0.312 | 15.5 | 7 | -1.25 (-1.74, -0.76) | <0.001 | 0.655 | 0.0 | ||
| medium | 11 | -2.77 (-4.66, -0.87) | 0.004 | <0.001 | 95.1 | 11 | -2.25 (-3.78, -0.72) | 0.004 | <0.001 | 94.7 | ||
| low | 2 | -2.74 (-4.31, -1.19) | 0.150 | 0.027 | 79.4 | 2 | -2.63 (-6.31, 1.06) | 0.162 | 0.146 | 52.7 | ||
| Age | <0.001 | <0.001 | ||||||||||
| <25 | 6 | -0.03 (-3.65, 3.58) | 0.985 | <0.001 | 97.0 | 6 | 0.37 (-2.02, 2.76) | 0.761 | <0.001 | 94.0 | ||
| 25–60 | 6 | -2.29 (-4.33, -0.25) | 0.028 | <0.001 | 82.0 | 6 | -2.31 (-4.18, -0.44) | 0.016 | <0.001 | 91.4 | ||
| >60 | 7 | -5.94 (-7.22, -4.6) | <0.001 | 0.382 | 6.0 | 7 | -4.67 (-6.14, -3.20) | <0.001 | 0.056 | 51.2 | ||
| Hypertension status | 0.890 | 0.250 | ||||||||||
| Normotensives | 0 | - | - | - | - | 0 | - | - | - | - | ||
| Hypertensives | 7 | -2.97 (-6.75, 0.81) | 0.124 | <0.001 | 94.6 | 7 | -2.92 (-4.48, -1.35) | <0.001 | <0.001 | 78.2 | ||
| Mix of hypertensives and normotensives | 13 | -2.63 (-4.67, -0.59) | 0.012 | <0.001 | 94.8 | 13 | -1.67 (-3.06, -0.29) | 0.018 | <0.001 | 94.7 | ||
| Duration | 0.160 | 0.08 | ||||||||||
| <2 months | 5 | -3.44 (-7.91–1.04) | 0.132 | 0.001 | 79.0 | 5 | -4.21 (-5.88, -2.54) | <0.001 | 0.133 | 43.3 | ||
| 2–6.6 months | 9 | -1.20 (-3.88,1.49) | 0.382 | <0.001 | 90.9 | 9 | -0.65 (-3.39, 2.08) | 0.640 | <0.001 | 95.6 | ||
| >6.6months | 6 | -4.49 (-6.56, -2.42) | <0.001 | 0.304 | 96.6 | 6 | -2.70 (-3.89, -1.51) | <0.001 | <0.001 | 91.7 | ||
| Sample size | 0.330 | 0.14 | ||||||||||
| <290 | 13 | -2.04 (-4.69, 0.61) | 0.131 | <0.001 | 93.9 | 13 | -1.39 (-3.42, 0.64) | 0.180 | <0.001 | 93.0 | ||
| >290 | 7 | -3.87 (-6.29, -1.44) | 0.002 | <0.001 | 96.1 | 7 | -3.21 (-4.47, -1.95) | <0.001 | <0.001 | 92.8 | ||
| Self-help materials | ||||||||||||
| Total | 10 | -1.36 (-3.46, 0.74) | 0.205 | 0.003 | 64 | 6 | -1.15 (-2.46, 0.16) | 0.085 | 0.011 | 59.6 | ||
| Quality | 0.93 | 0.60 | ||||||||||
| heigh | 5 | -1.61 (-3.78, 0.56) | 0.147 | 0.228 | 29.1 | 4 | -1.01 (-2.15, 0.13) | 0.082 | 0.601 | 0 | ||
| medium | 5 | -1.38 (-4.95, 2.19) | 0.448 | 0.012 | 72.1 | 5 | -1.76 (-4.33, 0.79) | 0.177 | 0.002 | 76.7 | ||
| low | ||||||||||||
| Age | <0.001 | 0.01 | ||||||||||
| <25 | 1 | 2.60 (0.92, 4.28) | 0.002 | - | - | 1 | 1.40 (-0.09, 2.89) | 0.067 | - | - | ||
| 25–60 | 6 | -2.60 (-4.51, -0.68) | 0.008 | 0.341 | 11.7 | 6 | -1.55 (-2.97, -0.13) | 0.032 | 0.123 | 42.3 | ||
| >60 | 3 | -0.83 (-3.51, 1.84) | 0.542 | 0.418 | 0.0 | 2 | -1.52 (-3.89, 0.85) | 0.208 | 0.260 | 21.1 | ||
| Hypertension status | 0.10 | <0.001 | ||||||||||
| Normotensives | 2 | 0.43 (-4.43, 5.28) | 0.863 | 0.022 | 81.0 | 2 | 0.99 (-0.30, 2.25) | 0.123 | 0.321 | 0 | ||
| Hypertensives | 4 | -3.87 (-6.40, -1.34) | 0.003 | 0.419 | 0 | 4 | -2.91 (-4.33, -1.49) | <0.001 | 0.517 | 0 | ||
| Mix of hypertensives and normotensives | 4 | -0.70 (-2.78, 1.38) | 0.511 | 0.557 | 0 | 3 | -0.45 (-1.87, 0.98) | 0.537 | 0.899 | 0 | ||
| Duration | - | - | ||||||||||
| <2 months | 10 | -1.36 (-3.46, 0.744) | 0.205 | 0.003 | 64 | 9 | -1.15 (-2.46, 0.16) | 0.085 | 0.011 | 59.6 | ||
| 2–6.6 months | 0 | - | - | - | - | 0 | - | - | - | - | ||
| >6.6months | 0 | - | - | - | - | 0 | - | - | - | - | ||
| Sample size | 0 | - | 0 | - | ||||||||
| <290 | 10 | -1.36 (-3.46, 0.74) | 0.205 | 0.003 | 64 | 6 | -1.15 (-2.46, 0.16) | 0.085 | 0.011 | 59.6 | ||
| >290 | 0 | - | - | - | - | 0 | - | - | - | - | ||
| Salt substitute | ||||||||||||
| Total | 14 | -7.44 (-8.82, -6.06) | <0.001 | <0.001 | 93.3 | 14 | -3.77 (-5.21, -2.32) | <0.001 | <0.001 | 97.2 | ||
| Quality | 0.700 | 0.391 | ||||||||||
| heigh | 7 | -7.80 (-9.84, -5.77) | <0.001 | 0.006 | 66.5 | 7 | -4.28 (-6.05, -2.50) | <0.001 | <0.001 | 76.2 | ||
| medium | 7 | -7.11 (-8.97, -5.25) | <0.001 | <0.001 | 96.3 | 7 | -3.27 (-5.31, -1.24) | <0.001 | <0.001 | 98.6 | ||
| low | - | - | ||||||||||
| Age | 0.150 | 0.010 | ||||||||||
| <25 | 1 | -7.14 (-7.71, -6.57) | <0.001 | - | - | 1 | -5.12 (-5.66, -4.58) | <0.001 | - | - | ||
| 25–60 | 5 | -9.25 (-11.35, -7.15) | <0.001 | 0.584 | 0 | 5 | -5.56 (-7.10, -4.02) | <0.001 | 0.677 | 0 | ||
| >60 | 7 | -7.09 (-9.57, -4.60) | <0.001 | <0.001 | 90.7 | 6 | -2.56 (-4.12, -1.01) | 0.001 | <0.001 | 88.8 | ||
| Hypertension status | 0.270 | 0.633 | ||||||||||
| Normotensives | 1 | -7.00 (-8.73, -5.27) | <0.001 | - | - | 1 | -4.60 (-6.52, -2.68) | <0.001 | - | - | ||
| Hypertensives | 10 | -8.16 (-9.71, -6.62) | <0.001 | 0.003 | 64.6 | 10 | -4.24 (-5.61, -2.87) | <0.001 | <0.001 | 83.4 | ||
| Mix of hypertensives and normotensives | 3 | -5.65 (-8.38, -2.91) | <0.001 | <0.001 | 97.9 | 3 | -3.04 (-6.13, -0.04) | 0.053 | <0.001 | 99.3 | ||
| Duration | 0.830 | 0.052 | ||||||||||
| <2 months | 3 | -8.19 (-10.80, -5.58) | <0.001 | 0.738 | 0 | 3 | -6.26 (-8.43, -4.08) | <0.001 | 0.467 | 0 | ||
| 2–6.6 months | 6 | -7.79 (-10.03, -5.55) | <0.001 | 0.002 | 74.2 | 6 | -2.95 (-4.67, -1.23) | 0.001 | <0.001 | 80.4 | ||
| >6.6months | 5 | -6.84 (-8.93, -4.74) | <0.001 | <0.001 | 97.4 | 5 | -3.85 (-6.27, -1.44) | 0.002 | <0.001 | 99.00 | ||
| Sample size | 0.010 | 0.140 | ||||||||||
| <290 | 10 | -8.37 (-9.67, -7.08) | <0.001 | 0.020 | 54.1 | 10 | -4.28 (-5.48, -3.07) | <0.001 | <0.001 | 72.1 | ||
| >290 | 4 | -5.37 (-7.67, -3.06) | <0.001 | <0.001 | 96.9 | 4 | -2.56 (-5.13, -0.01) | 0.051 | <0.001 | 98.9 | ||
CI: Confidence interval, SBP: Systolic blood pressure, DBP: diastolic blood pressure, WMD: Weighted mean difference
*Between groups comparisons are obtained from inverse variance method