Table 5. Summary of the findings of the present study.
| Outcome | Results | Number of participants (n studies) | Level of the evidence (scored using the GRADEa system) |
|---|---|---|---|
| Spontaneous pregnancy rate | OR 1.97 (95% CI: 1.28, 3.04); n=190 events; p<0.01; I2=20%; χ2 p=0.20 (Fig. 2) | 1,355 (16 RCTs) | ⊕⊕⊕⊝ (Moderate)b |
| Live-birth rate | OR 1.21 (95% CI: 0.53, 2.76); n=65 events; p=0.64 (Fig. 6) | 388 (4 RCTs) | ⊕⊝⊝⊝ (Very low)b,c,d |
| Miscarriage rate | OR 1.01 (95% CI: 0.34, 3.00); n=13 events; p=0.98 (Fig. 7) | 459 (4 RCTs) | ⊕⊝⊝⊝ (Very low)b,c,d |
| Sperm concentration | MD 5.93 mil/mL (95% CI: 4.43, 7.43); p<0.01; I2=94%; χ2 p<0.01 (Fig. 8) | 4,310 (35 RCTs) | ⊕⊕⊕⊝ (Moderate)b |
| Progressive sperm motility | MD 7.21% (95% CI: 3.66, 10.76); p<0.01; I2=99%; χ2 p<0.01 (Fig. 12) | 2,345 (20 RCTs) | ⊕⊕⊕⊝ (Moderate)b |
| Total sperm motility | MD 7.52% (95% CI: 3.11, 11.94); p<0.01; I2=100%; χ2 p<0.01 (Fig. 16) | 4,452 (36 RCTs) | ⊕⊕⊕⊝ (Moderate)b |
| Sperm morphology | MD 3.28% (95% CI: 2.40, 4.17); p<0.01; I2=96%; χ2 p<0.01 (Fig. 20) | 1,828 (18 RCTs) | ⊕⊕⊝⊝ (Low)b,c |
| Sperm DNA fragmentation | SMD -0.63 (95% CI: -2.29, 1.02); p=0.45 (Fig. 24) | 135 (3 RCTs) | ⊕⊝⊝⊝ (Very low)b,c,d |
| Seminal TAC levels | MD 1.87 (95% CI: 1.26, 2.48; p<0.01; I2=97%; χ2 p<0.01 (Fig. 26) | 316 (6 RCTs) | ⊕⊕⊝⊝ (Low)b,c |
| Seminal MDA levels | MD -0.39 (95% CI: -0.65, -0.14; p<0.01; I2=87%; χ2 p<0.01 (Fig. 27) | 403 (7 RCTs) | ⊕⊕⊝⊝ (Low)b,c |
CI: confidence interval, GRADE: Grading of Recommendations Assessment, Development and Evaluation, MD: mean difference, MDA: malondialdehyde acid, OR: odds ratio, RCT: randomized controlled trial, SMD: standardized mean difference, TAC: total antioxidant capacity.
aHigh level: We are very confident that the true effect lies close to that of the estimate of the effect. Moderate level: We are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low level: Our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect. Very low level: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect.
bDowngraded one level for risk of bias: lack of allocation concealment, lack of blinding and incomplete accounting of patients and outcome events.
cDowngraded one level for serious imprecision: small sample size.
dDowngraded one level for serious imprecision: crossing the line of no effect.