Table 2.
Risk of bias among studies analysed.
| Domain | Elements | Sweeney 2014 [5] | Brown 2014 [6] | Kurppa 2014 [9] | Derakhshan 2020 [11] | Fregnani 2016 [18] | Gültekin 2018 [19] | do Canto 2019 [20] | Heikinheimo 2019 [21] | Oh 2019 [22] | Kelppe 2019 [23] | Seki-Soda 2020 [24] | da Silva Marcelino 2021 [25] | Kunmongkolwut 2022 [26] | Santana 2021 [27] | Shirsat 2018 [28] | Diniz 2015 [29] | Yukimori 2017 [30] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Study question | Clearly focused and appropriate question | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Study population | Description of study population | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Sample size justification | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | |
| Comparability of subjects | Specific inclusion/exclusion criteria | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | N | A |
| Criteria applied equally to all groups | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | N | A | |
| Comparability of groups at baseline with regard to disease status and prognostic factors | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Study groups comparable to non-participants with regard to confounding factors | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Use of concurrent controls | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Comparability of follow-up among groups | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Exposure or intervention | Clear definition of exposure | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Measurement method standard, valid, and reliable | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | |
| Exposure measured equally in all study groups | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | |
| Outcome measurement | Primary/secondary outcomes clearly defined | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A |
| Outcomes assessed blind to exposure or intervention status | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Method of outcome assessment standard, valid, and reliable | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | |
| Length of follow-up adequate for question | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Statistical analysis | Statistical tests appropriate | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | N | N |
| Multiple comparisons taken into consideration | N | A | A | N | A | A | A | A | A | A | A | A | A | A | N | A | A | |
| Modelling and multivariate techniques appropriate | N | A | N | N | A | N | A | A | N | N | N | A | A | N | N | N | N | |
| Power calculation provided | N | A | A | N | A | A | I | A | A | A | A | A | A | A | N | N | N | |
| Assessment of confounding variables | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Dose–response assessment, if appropriate | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Results | Measure of effect for outcomes and appropriate measure of precision | A | A | A | I | A | A | A | A | A | A | A | A | A | A | A | I | A |
| Adequacy of follow-up for each study group | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | _ | |
| Discussion | Conclusions supported by results with biases and limitations taken into consideration | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | A | N |
| Funding or sponsorship | Type and sources of support for study | N | A | A | A | A | A | A | A | I | N | N | N | I | A | I | A | N |
Abbreviations: A, adequate; I, inadequate; N, not reported; -, not applicable to the study design.