Quality assessment of included studies
| Factor | Study* | ||||||
|---|---|---|---|---|---|---|---|
| Hassan et al. (31) | Murrell et al. (36) | Phelan et al. (35) | Spinella et al. (32) | Weinberg et al. (33) | Weinberg et al. (30) | Weinberg et al. (34) | |
| Selection | |||||||
| Representativeness of the exposed cohort | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Selection of the nonexposed cohort | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Ascertainment of exposure | ★ | ★ | ★ | ★ | ★ | — | ★ |
| Demonstration the outcome of interest not present at start of study | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Comparability | |||||||
| Comparability of cohorts on basis of design or analysis | ★★ | ★★ | ★★ | ★★ | ★★ | ★★ | ★★ |
| Outcome | |||||||
| Assessment of outcome | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Was follow-up long enough for outcomes to occur | ★ | ★ | ★ | ★ | ★ | ★ | ★ |
| Adequacy of follow up of cohorts | — | — | — | ★ | — | — | — |
| Total score | 8 | 8 | 8 | 9 | 8 | 7 | 8 |
↵* Based on the Newcastle–Ottawa Quality Assessment Scale for cohort studies, each study was awarded a maximum of 1 star for each item within the Selection and Outcome categories, and a maximum of 2 stars for the Comparability category. Total scores for each study were calculated by adding 1 point for each star awarded, with a maximum possible score of 9.