Table 3. Quality assessment using Newcastle-Ottawa Scale.
| Study | Representativeness of exposed cohort | Selection of the non exposed cohort | Ascertainment of exposure | outcome of interest was not present at start of study | Comparability of cohorts | Assessment of outcomes | Follow-up long enough for outcomes to occur | Adequacy of follow up of cohorts | Total |
|---|---|---|---|---|---|---|---|---|---|
| Kellermann AL et al (1989)[49] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Hurst V 4th et al (2007) [53] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Trenkamp RH et al (2015) [24] | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Birkenes TS et al (2012) [48] | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |