Table 5.
Level of evidence (GRADE).
| Outcome | Effect | Number of participants (studies) | Quality of the evidence (GRADE) | |
|---|---|---|---|---|
| Relative effect (95% CI) | Absolute effect (95% CI) | |||
| Total effectiveness | RR 1.27 (1.19 to 1.34) |
201 more per 100 (from 141 more to 253 more) |
914 (10 studies) |
⊕⊕OO Low1,4 |
|
| ||||
| Vertigo | RR 1.15 (1.03 to 1.28) |
124 more per 1000 (from 25 more to 231 more) |
188 (2 studies) |
⊕OOO Very low1,2,4 |
|
| ||||
| Headache | RR 1.3 (1.11 to 1.53) |
220 more per 1000 (from 81 more to 389 more) |
124 (2 studies) |
⊕OOO Very low1,2,4 |
|
| ||||
| Left vertebral artery | MD 2.86 higher (1.25 to 4.46 higher) |
208 (3 studies) |
⊕OOO Very low1,2,3,4 |
|
|
| ||||
| Right vertebral artery | MD 3.52 higher (1.52 to 5.51 higher) |
208 (3 studies) |
⊕OOO Very low1,2,3,4 |
|
|
| ||||
| Basilar artery | MD 2.6 higher (1.42 to 3.79 higher) |
208 (3 studies) |
⊕OOO Very low1,2,4 |
|
1Most of them did not mention randomization process, allocation concealment, and blinding.
2Published evidence is limited due to a small number of trials, all of which are showing benefits.
3The heterogeneity is significant.
4Publication bias exists.