Strong | Generally consistent findings were presented in multiple high-quality cohort studies |
Moderate | One high-quality cohort study and at least two high-quality case–control studies, or when at least three high-quality case–control studies show generally consistent findings |
Limited | Generally consistent findings were found in a single cohort study, or in maximum two case–control studies, or in multiple cross-sectional studies |
Conflicting | Less than 75% of the studies reported consistent findings |
No evidence | No study could be found |