Table 2.
Study quality assessment based on NOS
| Study | Selection (4) | Comparability (2) | Outcome (3) | Risk of bias | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1.1 Representat-iveness of the exposed cohort | 1.2 Selection of the nonexposed cohort | 1.3 Ascertain-ment of exposure | 1.4 Demonstration that outcome of interest was not present at start of study | 2.1 Controlled for main factors (age and gender) | 2.2. Controlled for additional factors (baseline neurologic status) | 3.1 Assessment of outcome | 3.2 Was follow-up long enough for outcomes to occur | 3.3 Adequacy of follow-up of cohorts | ||
| Alali [15] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | Not good |
| Bolduc [57] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Brenner [58] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | Good |
| Chang [17] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | Good |
| Ebner [59] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | Good |
| Elmer [60] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | Good |
| Fujita [61] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | Good |
| Fukuda [46] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | Not good |
| Gaieski [62] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Humaloja [16] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | Good |
| Janz [28] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | Not good |
| Jeon [63] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | Good |
| Johnson [64] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | Not good |
| Kiguchi [39] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Kupiec [65] | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | Not good |
| Lång [47] | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | Not good |
| Lee [66] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | Not good |
| Li [67] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | Good |
| Lopez [68] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | Good |
| Oh [69] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | Not good |
| Peluso [18] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | Not good |
| Popovic [38] | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | Not good |
| Rai [70] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Roberts [71] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | Not good |
| Russell [72] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | Not good |
| Sadaka [73] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Sadaka [74] | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A | N/A |
| Spindelboeck [75] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | Not good |
| Vaahersalo [40] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | Not good |
| Wang [76] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | Good |
| Yokoyama [19] | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | Not good |
| Youn [77] | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | Not good |
N/A, not applicable, NOS, Newcastle–Ottawa Scale