Table 3. Subgroup analysis in RCTs and PCSs .
| Subgroup | Studies design | No. of effects | RR (95% CI) | I2 | P value |
| CVD events by gender | |||||
| Both | RCT | 13 | 0.98 (0.93-1.04) | 0% | 0.573 |
| Male | RCT | 1 | 0.95 (0.84-1.07) | - | - |
| Female | RCT | 4 | 1.02 (0.96-1.10) | 0 % | 0.813 |
| CVD mortality by gender | |||||
| Both | RCT | 12 | 0.94 (0.84-1.04) | 0 % | 0.852 |
| Male | RCT | 1 | 0.85 (0.65-1.11) | - | - |
| Female | RCT | 4 | 1.04 (0.92-1.17) | 0 % | 0.777 |
| CVD events by vitamin D3 | RCT | 15 | 0.99 (0.95-1.03) | 0 % | 0.874 |
| CVD mortality by vitamin D3 | RCT | 15 | 0.97 (0.90-1.05) | 0 % | 0.851 |
| CVD events by ROB2 | |||||
| Low risk | RCT | 12 | 1.02 (0.97-1.07) | 0% | 0.763 |
| Some concerns | RCT | 5 | 0.94 (0.88-1.02) | 0% | 0.621 |
| High risk | RCT | 1 | 1.23 (0.39-3.88) | - | - |
| CVD mortality by ROB2 | |||||
| Low risk | RCT | 10 | 1.00 (0.92-1.09) | 0% | 0.776 |
| Some concerns | RCT | 4 | 0.86 (0.72-1.03) | 0% | 0.935 |
| High risk | RCT | 3 | 0.99 (0.11-9.24) | 0% | 0.344 |
| CVD events by follow-up (y) | |||||
| > 3 | RCT | 12 | 0.99 (0.95-1.03) | 0% | 0.882 |
| ≤ 3 | RCT | 6 | 1.16 (0.95-1.42) | 0% | 0.476 |
| CVD mortality by follow-up (y) | |||||
| > 3 | RCT | 11 | 0.97 (0.90-1.05) | 0% | 0.698 |
| ≤ 3 | RCT | 6 | 1.20 (0.62-2.64) | 0% | 0.782 |
| Myocardial infarction by vitamin D3 | RCT | 20 | 0.99 (0.93-1.06) | 0% | 0.999 |
| Stroke by vitamin D3 | RCT | 18 | 1.04 (0.97-1.12) | 0% | 0.986 |
| CVD events by gender | |||||
| Both | PCS | 5 | 1.44 (1.27-1.63) | 51.9% | 0.081 |
| Male | PCS | 2 | 1.03 (0.88-1.22) | 0% | 0.498 |
| Female | PCS | 4 | 1.19 (0.94-1.51) | 80.6% | 0.001 |
| CVD mortality by gender | PCS | ||||
| Both | PCS | 12 | 1.40 (1.18-1.67) | 72.3% | 0.001 |
| Male | PCS | 1 | 0.90 (0.39-2.05) | - | - |
| Female | PCS | 1 | 1.17 (0.72-1.90) | - | - |
| CVD events by follow-up (y) | PCS | ||||
| < 10 | PCS | 6 | 1.27 (1.02-1.57) | 78.9% | 0.001 |
| ≥ 10 | PCS | 4 | 1.25 (1.01-1.56) | 86.2% | 0.001 |
| CVD mortality by follow-up (y) | PCS | ||||
| < 10 | PCS | 5 | 1.16 (0.92-1.46) | 54.8% | 0.065 |
| ≥ 10 | PCS | 9 | 1.52 (1.30-1.77) | 38% | 0.115 |
| CVD event by quality (NOS) | PCS | ||||
| Moderate quality | PCS | 10 | 1.26 (1.10-1.45) | 82.5% | 0.001 |
| High quality | PCS | 1 | 1.03 (0.28-3.79) | - | - |
| CVD mortality by quality (NOS) | PCS | ||||
| Moderate quality | PCS | 9 | 1.33 (1.09-1.61) | 68% | 0.002 |
| High quality | PCS | 5 | 1.49 (1.19-1.87) | 36.9% | 0.175 |
| CVD events by CVD history at baseline | PCS | ||||
| No | PCS | 7 | 1.28 (1.07-1.53) | 84.5% | 0.001 |
| Yes | PCS | 4 | 1.22 (0.92-1.61) | 77.1% | 0.004 |
| CVD mortality by CVD history at baseline | PCS | ||||
| No | PCS | 6 | 1.17 (0.92-1.47) | 77.3% | 0.001 |
| Yes | PCS | 8 | 1.57 (1.36-1.81) | 2.7% | 0.409 |
Note. RCT: Randomized controlled trial;PCS: Prospective cohort study; RR: Risk ratio; CI: Confidence interval; CVD: Cardiovascular diseases; ROB2: Risk of bias 2; NOS: Newcastle-Ottawa scale.